Universal Studios

E.T. charmed Elliott (Henry Thomas) and millions of moviegoers in the 1982 movie "E.T.: The Extraterrestrial."

Thirty years ago, a different kind of alien hit the screen: a vulnerable, cuddly, candy-munching creature that captured hearts as well as box-office records. Is "E.T." still relevant for the 21st century? If you're looking for the extraterrestrial that humanity is most likely to run into first, E.T. definitely doesn't fit the mold. But if you're looking for the cultural icon that's most likely to motivate the search for honest-to-goodness extraterrestrials, E.T. just might be your A-list alien.

"If you look at the number of films that involve extraterrestrials these days, it's something like five or 10 a year," Seth Shostak, senior astronomer at the California-based SETI Institute, told me today. "And most of them are kinda nasty. What I liked about E.T. is that, after all, he was just a botanist who came to Earth and played with the kids.

"He was a good tonic against the xenophobia we have about aliens. He's no more realistic than those other aliens, but his appeal encouraged folks to think that searches such as SETI were maybe not a bad thing."

SETI — the search for extraterrestrial intelligence — is Shostak's specialty. In addition to conducting decades of research in the field, he's written books about aliens, advised moviemakers about them, and hosts a radio show that often touches upon the search for alien signals. If an unrealistically cute and cuddly alien gets more people interested in the quest, that's just fine by him.

"Look, none of these movie aliens are realistic," he said. "Certainly all of the good guys are relatively anthropomorphic. You could analyze it in terms of the science ... but to me, all of the alien films stimulate the idea that there could be something out there. I can see that only as a good."

So what would a realistic alien look like? Probably more like R2-D2 than E.T.: Intelligence that's encased in metallic hardware will travel much better than the kind of intelligence that's carried around in relatively fragile wetware. R2-D2 could be pretty cute at times, but it's more likely that the real-life robo-aliens would be indifferent to our fate. To some extent, Shostak agrees with physicist Stephen Hawking: Our relationship with alien visitors might be similar to the Native Americans' relationship to the Europeans in the 1500s. In short, not all sweetness and light.

"If any were to come, at least extrapolating from the history of visitations here on Earth, most likely they would be nasty," Shostak said. "It wasn't the nice guys who got on the ship to visit the Aztecs."

But then again, perhaps E.T. suggests a sunnier scenario. Why would the aliens visit? Probably not for resources, because any civilization capable of coming to Earth would already command prodigious reserves of power. Certainly not for mating. Even if E.T. was made of flesh and blood rather than metal, the genetic code (and reproductive system) would be different. Perhaps, like E.T., the aliens would come just to catalog the flora, the fauna, maybe even check out the rock and roll.

"That might make sense," Shostak said.

What do you think? Is anyone else out there, or are we alone? How have our perspectives on extraterrestrial life evolved over the past 30 years? Feel free to weigh in with your comments below.

More perspectives on E.T. and "E.T.":

• Aliens won't eat us, and we won't mate with them
• Expert doubts aliens would visit Earth to terrorize us
• Stephen Hawking: Aliens may pose risks to Earth
• Steven Spielberg considered creepy 'E.T. sequel
• Henry Thomas recalls leaving Spielberg in tears
• Cosmic Log archive on aliens

Correction for 10:20 a.m. Oct. 10: Shostak said there were five or 10 alien-themed movies per year, but I mistyped the quote to make it sound as if E.T. got far less screen time. Sorry about the miscue, which has been mended. 

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Gail Shumway / Getty Images

In a recently conducted poll, 19 percent of the respondents said they thought Washington, D.C., would be the most likely landing zone for a UFO. But if that ever happened, who's the best person to lead the welcoming party? About 65 percent said they'd rather have Barack Obama than Mitt Romney handle the situation.

A new poll suggests that 77 percent of Americans think there's evidence that aliens have already visited Earth. The same poll suggests most Americans think President Barack Obama would do a better job than presumptive GOP challenger Mitt Romney if we had to fight off an alien invasion. And if we have to rely on a superhero to save us, they'd rather go with the Hulk than Batman.

That somewhat silly survey was conducted to tout a "Chasing UFOs" TV series on the National Geographic Channel, but the results raise a serious question: If an alien civilization does get in touch with us, who's in charge of figuring out what to do?

"Nobody's in charge," says Seth Shostak, who is senior astronomer at the California-based SETI Institute as well as the chairman of the International Academy of Astronautics' SETI Permanent Study Group. Shostak and I talked about SETI — the search for extraterrestrial intelligence — as well as its serious and silly implications tonight on "Virtually Speaking Science." The hourlong talk show is archived as a podcast on the Web and on iTunes.

As the poll done for National Geographic suggests, a good number of people suspect the aliens have already arrived, presumably on UFOs or through interdimensional travel. Most scientists scoff at that idea. "Why would they appear only to cranks and weirdos?" British physicist Stephen Hawking asked earlier this month. But Shostak thinks it's only a matter of time before extraterrestrial civilizations actually do make themselves known, by sending signals across the light-years. Almost a decade ago, he predicted that we'd detect those signals by the year 2025, and today he told me he's sticking by that prediction.

During our pre-show interview, Shostak laid out his rationale for the 2025 date and discussed how an alien-contact scenario is likely to go down. Check out this edited transcript of the Q&A.

Cosmic Log: Do you still feel that 2025 is a good time frame for alien contact? And maybe more importantly, how do we know we're getting closer to the date?

SETI Institute

Seth Shostak is senior astronomer at the SETI Institute.

Shostak: People ask, 'Are you getting close?' And we no more know whether we're getting close than Chris Columbus knew he was getting close to the Americas — we might some palm fronds a day or two out, but other than that, we don't know. In some sense, it'll come as a complete surprise if we get a signal. We know that from false alarms. They never occur when you expect them, because you never expect them.

But in terms of the prediction, that's based on the following: We're looking for needles in a haystack. If you ask, when are you going to find a needle, you need to know three things: How big is the haystack? How fast are you going through the hay? And how many needles are in there? We know two out of three. The haystack's the galaxy, and we know how fast we're going through it. We don't know the number of needles. So I took estimates of the number from the Drake Equation, and figured that it's two dozen years out. What's happened in the meantime is that the funding crisis has slowed things down a bit.

Q: Do you think you need to revise the 2025 date?

A: I think 2025, 2030 is about right, given that we can continue to do the experiment.

Q: Is it a steady process, or is there an increasing rate of hay examination?

A: This is all predicated on an increasing rate. That's the march of technology, which is mostly digital electronics. Computers keep getting faster and faster at any given price point, and that's good news for us. We can look at a larger chunk of the radio dial at once. We can go through the stars faster. Or we can look at bigger hunks of sky at once. It's mostly computing power that is responsible for the increasing speed of SETI. We're not sitting around with earphones the way Jodie Foster was.

Q: Could it be that the patterns of communication by extraterrestrial civilizations take a form completely different from what we assume?

A: We kind of know what areas SETI is weak in. It's been slow, in the sense that you've got a couple of hundred billion star systems in the galaxy, and if you can look at only a couple a day, that's really slow going. That might take forever. Can we look at more stars in a given time, with adequate sensitivity?

The second thing is, it may be that you really have to look for a long time at any given star system. Of course, we don't do that. We look at any given star system, at any given frequency, for at most a few minutes. Some other search programs look for one and a half seconds at any given star system. If the aliens are broadcasting in our direction once a week, or once a day, or once an hour, we're not going to see it. We know that's a problem.

Another issue is that the aliens may not know we're here because they haven't picked up 'I Love Lucy' yet. They don't know Homo sapiens is here, they just know that Earth is a planet with biology. They may not be motivated to target us relentlessly with reality television. They may broadcast now and then, with a little ping just to see if anybody's here. You really need an experiment that can pick up an intermittent, maybe one-off signal that's designed to ping the planet. Everybody knows that. That's a technology issue, but it's an issue that's getting better.

Q: Has anybody come up with a concept for an all-sky, all-the-time receiver?

A: Yeah, well, all-sky, all the time, all frequencies — that's what you'd looove to have. On paper, you can design an instrument that can look at the entire sky. All frequencies, that's another problem, but you can certainly cover more frequencies than we do. It's all a question of whether you can afford to build such an instrument. The answer is, no, not now. It takes an enormous amount of computing power to do that. However, one thing you can say about the future is that there will be more computing power. This is not impossible. This is not like building rockets to go at 99 percent of the speed of light. That might work on paper, too, but in practice, that's a long way off. But this is something where you can say, with the computing power of a few decades hence, it becomes a practical thing.

Q: Assuming that alien signals are detected by 2025, is humanity ready for that?

A: Well, I don't know how much planning has been done. We've revised some protocols, but those are just the immediate steps you take if you pick up a signal. They deal with practical matters, like checking the signals out and alerting everybody. But I don't know that there's any large-scale effort to prepare humanity, any more than there was any preparation by the Indians in the Caribbean in case a Spanish ship showed up. I don't think that's a problem, to be honest. In poll after poll, the public has said they believe the aliens are out there. They see them on television every night, and at the movies every third weekend. A third of 'em think the aliens are already here, but they don't see a problem with that, either. Nobody's staying home. Everybody's still going to work.

I think that psychologically, everybody could handle it. It's just going to be a big news item. Whatever it would be, people would find it interesting. But they'd be savvy enough to realize there's no immediate threat. The aliens would be 500 light-years away, and we pick up their signal.  There's no reason to think that people would go just completely non-linear.

The long-term consequences are less predictable. People would ask, should we broadcast back? Should we send a rocket in that direction? What should we do?

Q: Who would be in charge if there was an alien signal? Assuming that scientists confirm that there's an anomalous signal pattern, hinting at extraterrestrial intelligence, what's the procedure?

A: I don't think that there's anybody designated to be in charge. There was a flap a few years ago, involving an official at the U.N., but that was all a red herring. She quickly admitted that she's not in charge. Nobody's in charge.

Look, the real people who will be in charge will be the media, because they'll be reporting it. In some sense, whoever finds the signal is probably in charge. If it's us, then somebody at the SETI Institute will be called. Or suppose it's the Berkeley group. Well, they're in charge. Or maybe it's a group that comes across the signal by accident. There's no hierarchy. Anyway, you know how the media work — they're not going to follow the rules.

There's no danger in any of this, except for one thing: That's the idea that you're sitting around, and suddenly there's a signal, and you call a press conference. That's not the way it will happen. We get signals all the time, and someday one of those signals will pass all the tests, and it slowly emerges as a real signal. But it takes something on the order of five days before you're convinced. During all that time, the media knows about this, because there is no secrecy. But there's no press conference yet, because the scientists aren't yet sure themselves. This time lag means there will be all sorts of stories before the official word is out. It isn't because of leakage, it's because anytime anybody finds something interesting, they may mention it. They'll put it on their blog. Who knows what they'll do?

It'll be very, very messy. And the corollary to this is that you can probably expect a lot of false alarms. There'll be something interesting, and a lot of people will write about it, and three days later it turns out to be nothing.

Q: Some people worry that our own radio signals are advertising our presence in what could be a rough neighborhood, but I take it that's not a concern of yours.

A: There are people who get their knickers in a knot about this deliberate broadcast stuff. National Geographic is supposed to be collecting tweets to broadcast as an answer to the "Wow Signal." I personally don't get heartburn about broadcasting. The fact is that NBC is broadcasting all the time, right? You can say, well, that's a weak signal. Sure it is. But if you're really worried about broadcasting into space, don't just shut down the publicity stunts. You better shut down the radars at the Seattle-Tacoma airport, too. They're broadcasting into space all the time.

Tune in "Virtually Speaking Science" on BlogTalkRadio or in Second Life — and bring lots of questions. Seth Shostak and I were at the StellaNova Small Auditorium, courtesy of the Meta Institute for Computational Astrophysics, at 9 p.m. ET (6 p.m. PT/SLT) tonight. If you missed the live event, don't worry: It's archived by "Virtually Speaking" on BlogTalkRadio as well as iTunes.

More nuggets from the National Geographic UFO poll: 

• The "Aliens Among Us" survey polled a random nationwide sample of 1,114 Americans between May 21 and May 29. The poll was conducted by Kelton Research, which used email invitations and online surveys. Quotas were set to ensure reliable and accurate representation of the total U.S. population ages 18 and older. Margin of error is +/- 2.9 percent.
• More than one-third of those surveyed (36 percent) believe UFOs exist. Eleven percent are confident they've spotted a UFO, and 20 percent know someone who claims to have seen one.
• Nearly two-thirds (65 percent) said Obama would be better-suited than Romney to handle an alien invasion. Seventy-nine percent believe the government has kept information about UFOs a secret from the public. Nineteen percent think Washington, D.C., is the most likely landing zone for a UFO, while 28 percent think a UFO would touch down in Roswell, N.M.
• Seventy-seven percent think there are signs that suggest aliens have visited Earth. Most of these people said that the evidence came in the form of photographs (60 percent) and videos (57 percent) of UFOs.
• If aliens landed, 22 percent said they would try to befriend the visitors. Fifteen percent said they would run away, 13 percent said they would lock their doors, and 2 percent said they would try to inflict bodily harm.
• Seventy-one percent think that aliens are more likely to exist than are superheroes, vampires and zombies. But if aliens attacked Earth, 21 percent said they would most likely call on the Hulk to deal with the havoc, compared with Batman (12 percent) or Spider-Man (8 percent). Fifty-five percent believe there really are officials like the "Men in Black" who claim to be agents and threaten those who come forward with UFO sightings. 

Previous episodes of "Virtually Speaking Science":

• Paul Doherty on solar eclipses and the transit of Venus
• Veronica Ann Zabala-Aliberto on spaceflight and Yuri's Night
• JPL's Dave Beaty on the search for life on Mars
• Shawn Lawrence Otto on science and politics
• Ig Nobel impresario Marc Abrahams on silly science
• Rocket scientist Robert Zubrin on Mars exploration
• Propulsion expert Marc Millis on interstellar spaceflight
• Sean Carroll on the puzzling frontiers of physics
• Rand Simberg on the private-enterprise vision for spaceflight
• Martin Hoffert on the future of energy policy
• George Djorgovski on science in virtual worlds
• Alan Stern on suborbital research and NASA's mission to Pluto
• Col. 'Coyote' Smith on the outlook for space solar power
• Tim Pickens on rocket ventures and the Google Lunar X Prize

Seth Shostak has a talk show, too! Hear it at "Big Picture Science."

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

If we ever come across traces of an advanced alien civilization like the one featured in "Prometheus," the new semi-prequel to the "Alien" movie series, our first course of action should not be to send them a shipload of human meat. Instead, send in the robots.

At least that's the prescription from Seth Shostak, senior astronomer at the California-based SETI Institute. "Would you indeed load up a starship with alien fodder and send it out?" he asked me. "Of course you wouldn't, because we don't know how to do that."

Sure, the crew of the starship Prometheus starts out in the year 2089, when we can assume that fusion power has solved our energy woes. But there's no chance that we'd be able to mount an interstellar trip by then, unless Spock and his pals from the planet Vulcan beam down and show us how. Even assuming that an ion-powered starship like the Prometheus could somehow get to other stars in a realistic (and relativistic) time frame, Shostak said he wouldn't send the humans on the first expedition to LV-223, the scene of the action in "Prometheus." 

"I think what you'd probably do is load up a spacecraft with sensors of all types, radio receivers, cameras, spectrometers, anything you can take up, essentially make it a Mars Viking mission, and just have it radio back what it finds," he said. "That's a heck of a lot less dangerous, and beyond that, it's a lot easier, because you don't have to put all this life support stuff and these cantankerous hominids on the rocket."

Even better, you could have that spaceship peopled by androids like David (played by Michael Fassbender in the movie), who basically steals the show in "Prometheus" anyway. That way, you avoid the ickiness of having monsters incubate inside human wetware, as they did in the original "Alien."

"If you can design an android that can do all the things that they do in these films, why is it that they haven't gone one step further and just replaced us with the androids?" Shostak asked. "Machinery can evolve much more quickly than biology. It's funny that they all get stunted at just the level where they're mostly helpful and occasionally malevolent."

Of course, without all that human cantankerousness and ickiness, you don't have much of a space horror movie. And be assured, there's plenty of both in "Prometheus." There's also a little real-life science in the movie, thanks in part to Kevin Hand, deputy chief scientist for solar system exploration at NASA's Jet Propulsion Laboratory. Hand served as a consultant on the film, and one of the first things he learned is that you should never let scientific qualms get in the way of a good movie.

"Being a scientist working with filmmakers, you have to keep in mind that the story comes first," Hand told me. "The science is a way to motivate certain elements and provide aspects of the plot. As long as you go in with that understanding, as a scientist, you can let your guard down a bit and not be constrained — which is different from our normal day-to-day scientific metabolism."

With that in mind, here are five themes in the movie that include a twist of scientific realism:

Habitability: Early into his involvement, Hand gave film director Ridley Scott and his team a tutorial on the different environments in our own solar system, ranging from steaming-hot Venus to cold, dry Mars and ice-covered Europa and Enceladus. The setting for the movie, LV-223, is a moon that orbits a giant planet in its parent star's habitable zone. That's similar to the fictional moon in the movie "Avatar," which orbits a Jupiter-like world named Polyphemus. It might also be similar to the theoretical moons circling 55 Cancri f, a planet detected about 41 light-years from Earth.

Hand noted that LV-223 is habitable in the Earthlike sense, meaning that it has an atmosphere and could conceivably support life at the surface. But he thinks that most livable environments are less like Earth and more like Europa, a Jovian moon that is thought to have a miles-deep ocean of water hidden beneath its forbidding surface ice. "Much of the habitable real estate in the universe might be within these ocean worlds that are covered with ice," Hand said. By his reckoning, Earth would be the peculiar planet.

Panspermia: I hope I'm not giving anything away when I say that "Prometheus" touches on the theme of panspermia — the idea that the building blocks of life, if not life itself, can be transferred from one planet to another. It's a great sci-fi theme, but it's not necessarily science fiction. Some theorists have proposed that life could have gotten its start on Mars, which was warmer and wetter billions of years ago, and then hitchhiked its way to Earth on the debris thrown up from a meteor blast. Or life could have come to Earth from farther out in the cosmos, borne by an impacting comet.

Hand pointed out that NASA's Kepler mission has detected thousands of potential planets in just one little patch of sky. That leaves plenty of opportunities for finding life out there, and plenty of opportunities for life to make its way here.

"Here we are on Earth, a planet in a solar system around a star that is 4.6 billion years old, which seems like an incredibly long period of time to us," Hand said. "But the universe is 13.7 billion years old. So there was a lot of time before the solar system even came about, 8 billion years or so of the history of the universe, during which many forms of life, many advanced civilizations, could have come and gone. They could still be there now, or they could have died off billions of years ago."

Propulsion: The Prometheus starship uses an ion propulsion system that gives a nod to the real-life ion drives used by probes such as the Dawn spacecraft, which is currently in orbit around the asteroid Vesta, Hand said. "The spacecraft that they're using is a much more advanced version of that kind of propulsion, but it's got a link to our current mode of exploring the solar system," he said.

It's unlikely that ion propulsion will be able to provide the power and maneuverability that Prometheus has anytime soon, and certainly not by 2089. But ion drives could offer a good option for interplanetary or interstellar flight. Their hallmark is slow but steady acceleration, starting out with as much force as it takes to hold up a piece of paper. Unlike chemical rocket engines, ion propulsion drives keep going, and going, and going, building up a figurative head of steam. Some experts suggest that nuclear or solar electric ion propulsion will provide the oomph for eventual missions to Mars.

Mapping: In the film trailer, there's a scene where the away team tosses out a few flying robotic spheres that scan the underground caverns with lasers and send back mapping data. Hand said he couldn't take total credit for that idea, but the robo-balls are based on the same principle that Stone Aerospace is using to design real-life submersible robots capable of observing and mapping subglacial lakes in Antarctica or, perhaps eventually, on Europa. "I mentioned some of that work to the artistic team," Hand recalled. There's just one big difference: The real-world robot, known as the Deep Phreatic Thermal Explorer, or DEPTHX, will be "going through underwater environments on Earth as opposed to exploring alien spaceships," Hand said.

Terraforming: At one point in the movie, Prometheus' away team finds out that they can take off their helmets and breathe the air inside an underground cavern. Hand was asked to come up with a plausible explanation for that plot point, and he proposed that an alien civilization could easily come up with a nuclear-powered device that electrolyzes water to produce oxygen. Heck, even we puny humans are thinking of ways to use rock-eating microbes to make Mars more livable. It won't happen overnight ... but maybe it could happen by 2089, if we play our cards right.

"Prometheus" focuses on an expedition to go after to the aliens, but what if the aliens were of a mind to come after us? Should we lie low, as famed physicist Stephen Hawking has suggested? Unfortunately, it's too late for that, Shostak said.

"For any society that could come here to do nasty things to us ... it's very easy to show that they could pick up all the stuff we've been sending out since the Second World War. In fact, they could pick up the lights of New York City," he said. "In a sense, we've already told the aliens we're here. The idea that it might be dangerous if we found some planet over there, so don't send them anything ... it's too late. That's not to say it might or might not be dangerous. We have no idea. But it's too late. It's silly to worry about it, because it would require that you lay low not just for the weekend, but forever. Forever! That would so cramp the sorts of things that our descendants could do, that I don't think that policy would have legs."

And if the aliens really do come after us? If they have the capability to project their firepower over a distance of light-years, forget what you saw in the movie "Battleship." We're toast.

More about the search for alien civilizations:

• Expert doubts alien visitors would terrorize us
• Queen of SETI retires from research
• City lights could point to E.T.
• What if E.T. thinks we're evil?
• What would you ask E.T.?
• Cosmic Log archive on aliens

More Hollywood reality checks:

• Reality check on 'Hunger Games' tech
• Invisibility and other 'Harry Potter' technologies
• 'John Carter' and the real-life Martian quest
• Virtual actor takes over in 'Tron: Legacy'
• Apollo 18 in fiction and fact
• 'Avatar' and the future of 3-D moviemaking
• Reality check for 'Star Trek' tech

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Alan Boyle / msnbc.com

SETI astronomer Jill Tarter looks out from the radio dish named after her at the Allen Telescope Array in northern California. The array's 42 linked dishes search for signals from extraterrestrial civilizations.

The real-life astronomer who inspired the central character in "Contact," the book and movie about the search for extraterrestrial intelligence, is retiring from her research post at the age of 68. But that doesn't mean Jill Tarter is giving up on the SETI quest. Instead, she's focusing on the search for funding for the non-profit SETI Institute.

For most of the institute's 28-year history, Tarter has been serving as director of the Center for SETI Research as well as holding the Bernard M. Oliver Chair for SETI. "I've worn two hats," she explained. Now she's passing along the center's top research hat to physicist Gerry Harp, a colleague at the institute — and wearing the Oliver Chair hat full-time as a fundraiser.

"We have got to get this endeavor stably funded," she told me.

Tarter knows as well as anyone on Earth how much of a challenge that will be. In the 1980s and 1990s, she participated in NASA-funded efforts to search for alien radio signals — efforts that drew intense fire from some members of Congress. The fire became so intense that NASA as well as the National Science Foundation were barred from funding SETI research in 1993. To keep hope alive, Tarter spearheaded a program to continue the search with private donations.

Breakthrough ... then, a bummer
A breakthrough came in 2007 with the dedication of the 42-antenna Allen Telescope Array in Northern California, a facility funded with $25 million in seed money from software billionaire Paul Allen and matching funds from other contributors. The SETI Institute partnered with the University of California at Berkeley to operate the array, and it looked as if the search for alien signals was finally on stable footing.

That didn't last long, however.

Berkeley had to drop out of the partnership due to money troubles. Last year, the institute mothballed the array and put out a plea for $200,000 in contributions to restart operations. "That certainly put an exclamation point on the funding crisis," Tarter said. The money was raised in a month and a half — thanks in part to a big financial and moral vote of support from actress-director Jodie Foster, who played the Tarter character (named Ellie Arroway) in the movie version of "Contact."

Now the telescope array is back in business with a new partner, SRI International, which maintains the facility in return for getting half of the array's observing time to track satellites and orbital debris for the U.S. Air Force. But Tarter wants to get the institute's SETI effort out of its scrimp-and-scrape mode. "Lots of startups do that, but they don't last very long if they don't get secure funding," she said.

One of Tarter's top objectives is to build up an endowment for SETI research. "I find it very interesting that at any one time, even in this economy, there are endowment campaigns of $100 million. We could be one of them," she said.

Stable funding would reassure the researchers who work with the institute that they'll be able to pursue their projects over the long term, Tarter said. "We have to make this a real destination for folks who want to do visionary things. ... They're in some sense hanging on a cliff, because there's no guaranteed scientific payoff, although there are lots of interesting instrumentation payoffs along the way," she said.

New twists for SETI
Lots of interesting twists are in store for the SETI quest. For example, researchers are working their way through a list of hundreds of candidate planets identified by NASA's Kepler mission. Tarter said about 10 percent of the Kepler field has been surveyed so far, at a rate of 30 targets a day.

"We don't yet have Earth 2.0, but we almost can taste it," she said. "That will change the whole approach. Does anybody live there? That's going to concretize so many things which are now a bit abstract."

The institute is already using a survey setup that checks three star systems at once for telltale patterns in radio emissions that could hint at an artificial source. The setup, known as SonATA, uses the triple-check to confirm the nature of any interesting effect that's detected. If the same effect is detected from three separate directions, that's a tip-off that the telescopes are picking up on earthly radio interference rather than E.T.'s phone call. 

"The next thing we're going to take on is real-time imaging of a wide field of view," Tarter said. "There are lots of challenges there, and lots of opportunities for SETI detections that haven't been there in the past."

Those are the sorts of challenges that Gerry Harp will be taking on as the new director of the Center for SETI Research. Meanwhile, Tarter will be focusing on the long-term future of the search for extraterrestrial intelligence.

"If we can get the research to the next level, there is something so fundamental that we can learn from the detection of a signal, even if it's just a cosmic dial tone," Tarter said. The message would be that technological civilizations can actually survive long enough to reach out to other corners of the cosmos.

"If they can do it, then dammit, we can do it," Tarter said.

More about the SETI quest:

• Gallery: 50 years of looking for E.T.
• Interactive: What are the odds of finding E.T.?
• Scientists need your eyes to look for E.T.
• Cosmic Log archive on SETI

The SETI Institute is celebrating Tarter's 35 years of SETI research at SETIcon II, set for June 22-24 at the Santa Clara Hyatt in California's Silicon Valley. SETIcon is a public convention that draws together more than 60 scientists, artists and entertainers to focus on the present and future search for life in the universe. Tarter will be honored at a gala event on June 23. Speakers will include fellow SETI astronomer Frank Drake; former astronaut Mae Jemison, a leader of the 100 Year Starship effort; and "Star Trek" actor Robert Picardo. Tickets are available via the SETIcon website.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.

David A. Aguilar / CfA

If an alien civilization builds brightly lit cities like those shown in this artist's conception, future generations of telescopes might allow us to detect them.

Astronomers suggest that artificial illumination creates a signature that could point to the existence of civilizations on other worlds — and they say we should get started on a survey of the edges of our own solar system, just in case.

The suggestion comes from Harvard's Abraham Loeb and Princeton's Edwin Turner, in a research paper submitted to the journal Astrobiology. A version of the paper appears on the arXiv.org preprint server and sparked a write-up today on Technology Review's Physics arXiv Blog.

Loeb, who chairs Harvard's astronomy department and is affiliated with the Harvard-Smithsonian Center for Astrophysics, acknowledged that detecting aliens by looking for the glow of their cities would be a long shot. But he pointed out that the cost of the exercise would be low.

"We say that we can piggyback on existing surveys that people are doing anyway. There's no need to use extra resources. ... My philosophy is simple: If we can do it, why not do it and check? Why put blinders on ourselves?" Loeb told me today.

Here's how the idea could work: An object's brightness varies with distance, but the relationship between those two factors will depend on whether the brightness is due to reflected sunlight or due to illumination from the object itself. For a self-illuminated object, the brightness varies by a factor of 1 over the distance squared, but "if you have an object that reflects light from another source ... the flux dies out like 1 over the distance to the fourth power," Loeb said.

Monitoring the changes in the brightness of an object on the edge of our solar system, in a broad disk of icy material known as the Kuiper Belt, could provide a "very simple test" to determine whether extraterrestrials have turned on the lights, Loeb said.

"We conclude that existing telescopes and surveys could detect the artificial light from a reasonably brightly illuminated region, roughly the size of a terrestrial city," on a Kuiper Belt object, Loeb and Turner write.

NASA

The lights of Cairo, Alexandria and the Nile shine through the night on Oct. 28, 2010, as seen from the International Space Station. Astronomers say such illumination could serve as a tip-off in the search for civilizations on other worlds.

How likely is it that E.T. would be found on the edges of our own solar system? Not that likely, but Loeb and Turner speculate that it could happen. "Artificially lit KBOs [Kuiper Belt objects] might have originated from civilizations near other stars," they write. "In particular, some small bodies may have traveled to the Kuiper Belt through interstellar space after being ejected dynamically from other planetary systems."

In addition to the E.T. search, Loeb said the Kuiper Belt survey would also be useful for studying how Kuiper Belt objects reflect light at different points in their orbits. "Even if the answer is, 'No, there is nothing peculiar,' we can still learn something from doing that," he told me. "And if there's something out there worth finding, that could change our perception of our place in the universe."

The technique could conceivably be extended to other stars once next-generation telescopes such as the James Webb Space Telescope and the Giant Magellan Telescope come online, over the next decade or so. There's been a lot of debate over whether the traditional search for radio signals from alien civilizations might be fruitless if E.T. moved beyond analog radio transmissions — and the search for artificial illumination could be worth checking out as a new frontier.

Someone could even try looking for the spectral signature of artificial light. (Do aliens use incandescent bulbs, compact fluorescent or LEDs?) But that particular kind of search would not be easy.

"For this signature to be detectable, the night side needs to have an artificial brightness comparable to the natural illumination of the day side," Loeb and Turner write. And when you consider that Earth's day side is about 600,000 times brighter than the night side, that means E.T. would have to cope with one heck of an electric bill.

What do you think about the search for E.T.'s city lights? Feel free to add your comment below.

More about the search for extraterrestrial intelligence:

• Donations revive the SETI quest
• Gallery: Four decades of SETI
• Alien-hunters add super-Earths to their list
• A new idea in the search for E.T.'s footprints
• More from Cosmic Log about aliens ... and about SETI

Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding me to your Google+ circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds. 

A study that reviews a host of sci-fi scenarios for contact with extraterrestrials stirred up such a ruckus today that NASA had to step in and distance itself from the research. The controversy focuses on the idea that E.T. could well decide that we're a threat to interstellar order, and therefore we have to be stopped before we spread.

The report itself, published in the journal Acta Astronautica, covers ground that's familiar to dedicated fans of E.T. lore. For example, the premise of the 1951 sci-fi classic "The Day the Earth Stood Still" is that universalist-minded aliens see our civilization as so rooted in violence that it's better to snuff us out than let us ruin the neighborhood. (The 2008 remake, starring Keanu Reeves, recycled that idea with an environmental theme.)

Then there's the "Hitchhiker's Guide to the Galaxy" scenario, in which Earth is destroyed merely to make way for a new stretch of intergalactic infrastructure.

"At the heart of these scenarios is the possibility that intrinsic value may be more efficiently produced in our absence," the researchers write.

The most familiar sci-fi scenario is the one in which the aliens are as selfish and territorial as we are, and want to wipe us out or enslave us and take our stuff. Think "War of the Worlds" or "Independence Day." In such cases, the researchers note that there's the potential for big payoffs ... if we prevail.

"Humanity benefits not only from the major moral victory of having defeated a daunting rival but also from the opportunity to reverse-engineer ETI [extraterrestrial intelligence] technology," they write. Indeed, New York Times columnist Paul Krugman joked last weekend that a fake alien invasion might be just the thing to spark an economic turnaround.

The researchers touch on more benign scenarios as well — for example, the "Star Trek" scenario, in which helpful aliens welcome us into the United Federation of Planets because we're all basically good guys (as opposed to those evil Klingons, until they become good guys, too). And then there's something like the "E.T." scenario, in which the aliens mostly just want to stay out of our way.

The 33-page study reflects at length on the potential risks.

"The possibility of harmful contact with ETI suggests that we may use some caution for METI [sending messages to extaterrestrial intelligence]," the researchers write. "Given that we have already altered our environment in ways that may be viewed as unethical by universalist ETI, it may be prudent to avoid sending any message that shows evidence of our negative environmental impact. The chemical composition of Earth's atmosphere over recent time may be a poor choice for a message because it would show a rapid accumulation of carbon dioxide from human activity. Likewise, any message that indicates widespread loss of biodiversity or rapid rates of expansion may be dangerous if received by such universalist ETI."

In short, let's keep our environmental bad habits on the down low, so as not to get the sad-Keanu E.T.'s on our case.

The basis of the brouhaha
By themselves, these ideas are not all that, um, alien. For years, sci-fi author David Brin has advised keeping quiet about our existence, and celebrity physicist Stephen Hawking agrees. U.N. officials and scientific experts also say the messages we direct toward any aliens we come across would have to be carefully managed.

So what's the big deal? Well, one of the authors of the paper, Shawn Domagal-Goldman, happens to be a postdoctoral student working at NASA Headquarters — and that highly tenuous connection to the world's most influential space agency sparked a huge wave of scare headlines. It started with The Guardian's story, and rolled onto The Drudge Report's webpage with a headline reading "NASA REPORT: Aliens may destroy humanity to protect other civlizations..." Another variant was this one: "NASA: Aliens May Destroy Humanity Over Greenhouse Gases."

Eventually, NASA had to send out a Twitter update saying "Yes, @drudge and @guardiannews are mistaken about an 'alien' report. It's not NASA research. Ask the report's author...." The space agency followed up later with two more tweets, emphasizing that it was not involved in the study and saying that Fox News and CNN "have it wrong."

In each case, NASA linked to a lengthy clarification and apology from Domagal-Goldman, who made clear that the study was not a "NASA report," that no NASA funding was expended on it, and that he spent none of his working hours on writing the paper. He said his two co-authors, Seth Baum and Jacob Haqq-Misra of Pennsylvania State University, "put in the vast majority of work on it."

"It was just a fun paper written by a few friends, one of whom happens to have a NASA affiliation," Domagal-Goldman wrote.

He admitted that including the NASA affiliation turned out to be a "horrible mistake":

"I did so because that is my current academic affiliation. But when I did so I did not realize the full implications that has. I'm deeply sorry for that, but it was a mistake born out of carelessness and inexperience and nothing more. I will do what I can to rectify this, including distributing this post to the Guardian, Drudge and NASA Watch. Please help me spread this post to the other places you may see the article inaccurately attributed to NASA.

"One last thing: I stand by the analysis in the paper. Is such a scenario likely? I don't think so. But it's one of a myriad of possible (albeit unlikely) scenarios, and the point of the paper was to review them. But remember — and this is key — it's me standing for the paper ... not the full weight of the National Aeronautics and Space Administration. For anything I have done to mis-convey that to those covering the story, to the public, or to the fine employees of NASA, I apologize."

This isn't the first case where the NASA connection has become entangled in scientific speculation. In March, the space agency took great pains to distance itself from NASA researcher Richard Hoover's claims to have found evidence of outer-space organisms in meteorites.

In Domagal-Gordon's case, the substance was far less controversial. As I've tried to point out above, the views expressed in the paper aren't that far off from the typical science-blog fare. I'm willing to bet a goodly sum of quatloos that Domagal-Gordon will go on to have a fine career in science ... and also that this won't be NASA's last P.R. kerfuffle over E.T.

More about aliens:

• Hollywood remakes an alien
• What would you ask the aliens?
• Why we love to fear E.T.
• The alien files on Cosmic Log

Connect with the Cosmic Log community by "liking" the log's Facebook page or following @b0yle on Twitter. You can also add me to your Google+ circle, and check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

SETI Institute

Radio antennas stand sentinel at the Allen Telescope Array, north of San Francisco.

The SETI Institute's search for extraterrestrial intelligence is back on track, thanks to more than $200,000 in donations from thousands of fans.

"We're not completely out of the woods yet, but everybody's smiling here," the institute's chief executive officer, Tom Pierson, told me today.

In April, the institute had to put its big ear for hearing E.T.'s radio call, the 42-antenna Allen Telescope Array in Northern California, into "hibernation" due to budget woes. The biggest hit was the loss of funding by the University of California at Berkeley, the institute's partner for operating the antenna array.

The SETI Institute has been around for decades: It stepped in to help keep the search for alien radio signals active after NASA cut off funding for the quest in 1993. It's not the only organization doing SETI, but it's the leader in the field. The Allen Telescope Array, or ATA, was launched with $50 million in contributions from software billionaire Paul Allen and others — and if the array ever takes in 350 linked antennas, as it's designed to do, it would rank among the world's premier radio-telescope facilities.

But in light of the financial challenges, that's a huge "if" right now. In fact, until last week it wasn't certain if or when the ATA would come back online.

After the antenna array was mothballed, the institute and its fans in Silicon Valley set up a Web-based campaign for donations, known as SETIstars. The campaign kicked off in June, and about 45 days later, on Aug. 3, contributions hit the $200,000 mark. That was how much money the SETI Institute said would be needed to bring the antenna array back into operation. (Since then more than $4,000 in additional contributions have come in.)

Among the contributors are Jodie Foster, the actress who played a SETI researcher in the movie "Contact"; science-fiction writer Larry Niven, creator of the "Ringworld" series of novels; and Apollo 8 astronaut Bill Anders, who flew around the moon in 1968. "It is absolutely irresponsible of the human race not to be searching for evidence of extraterrestrial intelligence," Anders wrote in a note accompanying his contribution.

Pierson said the institute's managers and scientists were drawing up a plan that would restart science operations in September.

"We think we're going to come out of hibernation and be solid for the next five months or so, and during those five months we're going to take care of calendar year 2013 and put that under our belt," he said.

Pierson acknowledged that the ATA's long-term success would "require a mix of funding," including continued contributions as well as renewed cash flow from other applications for the radio array. The institute is hoping that the U.S. Air Force will use the array to  track orbital objects that otherwise might pose a threat to the International Space Station and other satellites. During the daytime, the ATA could be used for the Air Force's "debris deconfliction," and during the night it could search for alien signals, Pierson said.

The institute is also looking for ways to reduce the array's operating costs from the current level of $1.5 million per year, plus another $1 million for science operations, Pierson said. "We need to transition to a new modality without UC-Berkeley," he said.

Eventually, astronomers at the SETI Institute hope to use the ATA to listen for signals from the most promising planetary systems identified by NASA's Kepler planet-hunting mission. Jill Tarter, the institute's director of SETI research, said in April that the fund-raising target for the Kepler follow-up project would be $5 million.

The institute has already set up a website called setiQuest, where citizen scientists can help sift through the data expected from the ATA, and SETIstars will remain open to receive donations, Pierson said. He had two messages for the SETI supporters: "No. 1 is how grateful we are," he told me. "More than 2,000 people jumped in and help. Also, stand by for future campaigns from SETIstars. We hope to build opportunities that will really excite the public."

More about the search for alien signals:

• New E.T. hunt tunes in on Earthlike planets
• Calculate the odds of finding E.T.
• Are we alone in the universe? Well, maybe
• Gallery: 50 years of searching for E.T.
• Search for extraterrestrials on msnbc.com

Connect with the Cosmic Log community by "liking" the log's Facebook page or following @b0yle on Twitter. You can also add me to your Google+ circle, and check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Univ. of St. Andrews photoillustration

On a world that spins around two dim suns, the vegetation may well look black to human eyes.

Researchers suggest that vegetation on an alien planet like Tatooine in "Star Wars" might well look black or gray to human eyes. But they probably wouldn’t seem devoid of color to the eyes of the aliens — assuming they have eyes, that is.

The conjecture comes from a paper presented by the University of St. Andrews' Jack O'Malley-James at the Royal Astronomical Society's National Astronomy Meeting in Wales. O'Malley-James is working on a Ph.D. project to assess the potential for photosynthetic life in multiple-star systems with different combinations of sunlike stars and red dwarfs.

On Earth, the leaves of plants generally look green because two types of chlorophyll absorb the reddish and bluish wavelengths in the visible-light spectrum. Those red and blue wavelengths drive the photosynthetic process by which plants convert the sun's energy into chemical energy. In contrast, the green wavelengths are reflected into the RGB optical sensors known as our eyes.

Scientists surmise that the birds and bugs may see plants quite differently, with greater sensitivity to different shades of green and the ability to sense ultraviolet wavelengths as well.

O'Malley-James suggests that in different corners of our galaxy, plants could evolve to take advantage of different combinations of wavelengths, depending on the light coming from their parent sun ... or suns. The possibilities become particularly intriguing for a planet in a multiple-star system — like Tatooine, Luke Skywalker's fictional home planet in the "Star Wars" movie saga.

J. O'Malley-James / Univ. of St. Andrews

On planets orbiting red-dwarf stars, the vegetation may have more photosynthetic pigments in order to make use of a fuller range of wavelengths, giving them a "black" appearance. Here are some earthly examples of dark plants and flowers.

"If a planet were found in a system with two or more stars, there would potentially be multiple sources of energy available to drive photosynthesis. The temperature of a star determines its color and, hence, the color of light used for photosynthesis. Depending on the colors of their starlight, plants would evolve very differently,"  he said in a news release.

Statistics show that more than 25 percent of sunlike stars and 50 percent of the red dwarfs in our galaxy are found in multiple-star systems. Armed with such statistics, O'Malley-James and his colleagues ran computer simulations to determine the optimal strategy for photosynthesis over a wide spectrum (heh, heh) of planetary alignments.

“Our simulations suggest that planets in multi-star systems may host exotic forms of the more familiar plants we see on Earth," O'Malley-James reported. "Plants with dim red dwarf suns for example, may appear black to our eyes, absorbing across the entire visible wavelength range in order to use as much of the available light as possible. They may also be able to use infrared or ultraviolet radiation to drive photosynthesis. For planets orbiting two stars like our own, harmful radiation from intense stellar flares could lead to plants that develop their own UV-blocking sunscreens, or photosynthesizing microorganisms that can move in response to a sudden flare."

But even if the plants reflected none of the visible-light wavelengths, extraterrestrial gardeners might well have their own special appreciation for an ultraviolet bloom, or leaves that are variegated in the thermal infrared.

I know it sounds like a flight of fancy, but this is just the kind of flight I enjoy the most. The subject reminds me of the scene from "Battlestar Galactica" where Brother Cavil complains about the "ridiculous gelatinous orbs" in his head. "I want to see gamma rays!" he shouts. "I want to hear X-rays!" Which new senses do you think the aliens might have ... and which do you wish you could have? Feel free to weigh in with your own conjectures in the comment section below.

More about alien perspectives:

• Want to call E.T.? Keep it simple, stupid Earthling
• Rare exoplanet has 'Star Wars' twin sunset
• How to find aliens: Follow the photosynthesis
• Alien plants get new twist in world of 'Avatar'
• Plants on other planets might not be green

O'Malley-James' supervisors on the Ph.D. project include Jane Greaves of the University of St. Andrews, John Raven of the University of Dundee and Charles Cockell of The Open University.

Join the Cosmic Log community by clicking the "like" button on our Facebook page or by following msnbc.com science editor Alan Boyle as b0yle on Twitter. To learn more about my book on Pluto and the search for planets, check out the website for "The Case for Pluto." 

Science / AAAS

A photomicrograph shows a strain of bacteria called GFAJ-1 that was said to incorporate arsenic into its cellular machinery.

Last updated 2:15 p.m. April 2:

Is there life beyond Earth? Over the past few months, scientists have repeatedly suggested that there could be — but the science behind those suggestions remains frustratingly murky and controversial.

Astrobiology's X-Files were the subject of a talk I gave on Saturday in the Second Life virtual world, at the invitation of the Meta Institute for Computational Astrophysics. Here's the vidcast of the talk — which gives you a taste of how Second Life works as well as how the search for extraterrestrial life works.

Arsenic life
This talk came exactly four months after researchers shook up the scientific world with claims that they were able to get the cellular machinery of microbes from California's Mono Lake working with arsenic instead of phosphorus. That's an amazing result, because arsenic is supposed to be poisonous to living things. If organisms on Earth could be tweaked in such a dramatic way, perhaps life could arise in other environments that don't seem conducive to life as we know it ... the Saturnian moon Titan, for example.

The implication of the research, published in the journal Science, would be that we might be missing strains of "weird life" that just might exist under our noses. (Perhaps literally under our noses, as a "second Genesis" that has gone undetected.)

The study ran into a lot of skepticism from the start. Some microbiologists and chemists have faulted the research team's laboratory techniques, or the conclusions that the team drew from their data. In response, the research team insisted their science was sound — but also encouraged their detractors to run their own experiments and report the results. Science pledged to publish a follow-up.

That follow-up is still in the works, but commentaries on the "arsenic life" are showing up in peer-reviewed journals such as BioEssays and FEMS Microbiology Letters. These papers have sparked a secondary controversy: Does scientific criticism really count if it's just on the Internet?

The BioEssays paper sees no "fatal flaw" in the original paper, and the paper's authors contend that Internet-only discussions "are not components of the peer-reviewed literature and thus are not placed on record as part of the official scientific discourse." The Microbiology Letters commentary complains about "the magic and nonsense that floods cyberspace."

As you can imagine, that's sparked a lot of counter-criticism from the folks who have been using the blogosphere and Twittersphere as a sounding board for their own review of the research. To get that side of the story, check out the postings from Rosie Redfield at the University of British Columbia, Zen Faulkes from the University of Texas-Pan American and Michael Eisen from the University of California at Berkeley (who attended an informal seminar given by Felisa Wolfe-Simon, the lead author of the arsenic-life study).

R. Hoover / Journal of Cosmology

A field-emission scanning electron micrograph shows one of the filaments that was found in the Ivuna CI1 carbonaceous meteorite. The filament looks similar to those seen in earthly cyanobacteria.

Meteorite life
Less than a month ago, NASA astrobiologist Richard Hoover published a paper in the online-only Journal of Cosmology, suggesting that a number of meteorites contained microbes that could have come from outer space. Once again, the study created a splash, in large part because of the NASA connection. There was quite a furor over whether or not Hoover was misinterpreting what he was seeing, and some critics pointed out that the research had been submitted to (and rejected by) other, better-known journals before it wound up in the Journal of Cosmology.

The story went big on a Saturday, but by the following Monday, executives at NASA disavowed the research, and the debate quickly died down. The Journal of Cosmology's editors said they were selling off the publication. Hoover, who has had a long and distinguished career as a researcher at NASA's Marshall Space Flight Center, faced sharp questions about his academic credentials.

Today, Hoover came in for an added dose of indignity: The James Randi Educational Foundation named him one of the year's "five worst promoters of nonsense," alongside anti-vaxxer Andrew Wakefield, televangelist Peter Popoff, TV doctor Mehmet Oz and the CVS pharmacy chain (for offering homeopathic remedies). The last thing Hoover needs right now is a "Scientist Pigasus Award" from the Amazing Randi.

NASA / LPI

Some scientists have suggested that tiny wormlike structures seen within the Mars meteorite known as ALH84001 may be "nanofossils" of biological origin.

Life on Mars
You could argue that the sharp debate over the prospects of detecting microbial life from beyond Earth began 15 years ago, with Science's 1996 publication of research about "nanofossils" found in a meteorite from Mars. Some might go two decades further back, to the much-debated life-detection experiments that went to Mars aboard the Viking landers.

Even after 15 years, the microfossil debate is still percolating. The researchers behind the original study have been setting out other lines of evidence to argue that they're seeing the fossilized traces of ancient organisms rather than modern-day contamination from Earth, or geological shapes that just happen to look like critters.

Other studies, conducted as part of NASA's Phoenix Mars Lander mission, have shown the presence of perchlorate, a chemical that could be associated with particular kinds of exotic life on Earth. Those findings have revived discussions over what Viking found (or failed to find).

Although the debate over past life-on-Mars experiments is continuing, most astrobiologists say it's going to take additional  studies on the Red Planet to resolve the controversy. That's the goal of an experiment being proposed by MIT and Harvard researchers, known as the Search for Extra-Terrestrial Genome, or SETG. Right now the researchers are facing one big challenge: They don't yet have a spot on a future Mars probe.

Even if SETG's genome sequencer went to Mars and detected a snippet of DNA or RNA, would that serve as sufficient evidence that life arose on other planets? Or would such a claim end up in the same limbo that surrounds earlier claims for alien life. I suspect that the latter would be the case — but what do you think? Feel free to weigh in with your comments below, and check out Saturday's hourlong presentation.

More controversies in astrobiology:

• Strange find on Titan sparks chatter about life
• Mars methane mystery: What's making the gas?
• Search for alien life may take giant leap forward
• What exactly is life, anyway?

Join the Cosmic Log community by clicking the "like" button on our Facebook page or by following msnbc.com science editor Alan Boyle as b0yle on Twitter. To learn more about my book on Pluto and the search for planets, check out the website for "The Case for Pluto."

R. Hoover / Journal of Cosmology

An image created using a field-emission scanning electron microscope shows a coiled filament that was found within a carbonaceous meteorite. The scale bar indicates a length of 20 microns.

Last updated 7 p.m. ET March 8:

A NASA researcher's claim that organisms from outer space have been found within a rare class of meteorites certainly sparked a lot of comments over the weekend, from experts on astrobiology and microbiology as well as from the public at large. Some of the commentators have been pretty scathing. David Morrison, senior scientist for the NASA Astrobiology Institute, told me in an e-mail that the paper really should have been published on April Fool's Day. Pharyngula's P.Z. Myers, a biologist at the University of Minnesota at Morris, said "this work is garbage" and voiced surprise that anyone was taking it seriously.

Now the Journal of Cosmology, which published the much-debated paper by NASA biologist Richard Hoover, has added a batch of commentaries from a variety of researchers and others. Here are some of the folks in the journal's lineup:

• Cody Youngbull of the University of Arizona's Biodesign Institute notes that Hoover's claims have "gone viral, with major media news sources and Internet blogs all carrying reports of this story. And so too the experts, for whom this information is not new, who have been monitoring the accounts of fossils in these same meteorites since 1961, have something to get excited about. ... This is because, while the elemental and mineral composition data remains identical to prior accepted reports, the morphological data far exceeds anything yet shown on the subject."
• Harrison Schmitt, the Apollo 17 scientist-astronaut who went from walking on the moon to serving in the U.S. Senate and who is now a researcher at the University of Wisconsin at Madison, says he can't pass judgment on the research itself. Instead, he wonders "why many do not seem to want life to have originated independently on Earth. ... We just have to figure out how it all happened."
• Patrick Godon, an astrophysicist at Villanova University, says Hoover "presents firm evidence" that fossil microbes are embedded within the meteorites, but he says it's "debatable" whether the microbes came from Earth or from somewhere else in outer space.
• Elena Pikuta, a microbiologist from the University of Alabama at Huntsville who has collaborated with Hoover, says the study "represents a sensational discovery which will have the potential to change our understanding on the origin of biosphere." The findings from the meteorites were "analyzed and interpreted according to the current standards in science using highly sensitive laboratory techniques," she says.
• Tulane University physicist Frank Tipler, author of the controversial book "The Physics of Immortality," says that "although Hoover has done as much as is possible with his small sample, we cannot yet conclude that he has indeed seen fossil cyanobacteria."

The journal may have decided against immediately publishing some of the responses it received, based on the missing numbers in the order of the commentaries. As of late today, No. 15 out of 21 was still missing  — and No. 11, attributed to Cardiff University astrobiologist Chandra Wickramasinghe and carrying the subtitle "A Vindication of Panspermia," wasn't yet displayed on the page.

Generally speaking, the journal's commentaries don't provide the kind of hard-hitting criticism that some of the better-known outside experts on microbiology have been voicing in other forums. But they do suggest that Hoover's claims will continue to be debated rather than going immediately into the trash can.

Update for 11 a.m. ET: In a statement distributed by the SpaceRef website, one of NASA's top scientists says the space agency does not support Hoover's findings. Here's the word from Paul Hertz, chief scientist of the Science Mission Directorate at NASA Headquarters in Washington:

"NASA is a scientific and technical agency committed to a culture of openness with the media and public. While we value the free exchange of ideas, data and information as part of scientific and technical inquiry, NASA cannot stand behind or support a scientific claim unless it has been peer-reviewed or thoroughly examined by other qualified experts. This paper was submitted in 2007 to the International Journal of Astrobiology. However, the peer review process was not completed for that submission. NASA also was unaware of the recent submission of the paper to the Journal of Cosmology or of the paper's subsequent publication. Additional questions should be directed to the author of the paper."

Meanwhile, Universe Today's Nancy Atkinson got in touch with Chris McKay, an astrobiologist at NASA's Ames Research Center. Here's a sampling from McKay's comments:

"The implication of these results is that the meteorite hosted a liquid water environment in contact with sunlight and high oxygen. ... Richard Hoover is a careful and accomplished microscopist so there is every reason to believe that the structures he sees are present and are not due to contamination. If these structures had been reported from sediments from a lake bottom there would be no question that they were classified correctly as biological remains."

McKay also acknowledged, however, that the structures could turn out to be "chance shapes" that just happen to look like pieces of an organism. That kind of interpretation was put forward to explain the "nanofossils" seen in a meteorite from Mars back in 1996. Moreover, if the structures do turn out to be cyanobacteria, and they're not contaminants, it'd be hard to explain in biological terms how they could survive on a meteorite in space.

Update for 11:30 a.m. ET: One of the questions that has come up is, "If they really did find alien life, why isn't this research being published by one of the big scientific journals, such as Science or Nature, rather than some little online publication that's on the brink of going out of business?" Lana Tao, managing editor for the Journal of Cosmology, addressed that question in an e-mailed statement:

"The Journal of Cosmology has received e-mails asking why Dr. Hoover's paper was not published in Science or Nature. We are aware that individuals who may or may not be associated with these publications are posting ad hominem attacks, which essentially wish the public to believe that if Dr. Hoover's article was really important it would have been published by these other journals. These are tantamount to schoolyard taunts by jealous children.

"1) First, Dr. Hoover's article was an original contribution and had not been submitted to these two periodicals.

"2) Secondly, both Science and Nature have a nasty history of rejecting extremely important papers, some of which later earned the author's a Noble Prize [sic]. Use Google keywords search for a wealth of info.  Nature magazine admits to this, though they put a positive spin on these rejections.

http://www.nature.com/nature/journal/v425/n6959/full/425645a.html

"3) Editors at Science have been accused of using the Bible to make editorial decisions by scientists such as Dr. Gil Levin (who devised the famous NASA Viking Mars Experiments). 

"4) It is a matter of public record that the organization which publishes science magazine have engaged in illegal anti-competitive practices designed to harm the Journal of Cosmology. The continuing success of JOC poses a competitive threat to their business model. We should not be surprised their 'hand puppets' are complaining that JOC published this article, and not them.

"5) Science and Nature are in the business of making money. The Journal of Cosmology is free, open access, and is in the business of promoting science.

"6) Science and Nature protect the status quo, and have a history of rejecting great papers.

"7) In less than 2 years, the Journal of Cosmology has become one of the top online science journals, with nearly a million hits for January. Our mission is to advance science.

"8) The ad hominem attacks and complaints by those say Dr. Hoover's article should have been published in these other periodicals, and not JOC, are just sour grapes and should not be taken seriously.

"9) We have repeatedly offered to publish critical commentary. We are still waiting."

Update for noon ET: Bad Astronomy's Phil Plait says he's come to the conclusion that "Hoover's claims are wrong," based on many of the factors we've been talking about (criticism of methods from microbiologists, questions about the venue for publication, scant peer review and lack of NASA support, etc.). One of the more interesting angles comes from his e-mail exchange with Penny Boston, an astrobiologist and geologist at New Mexico Tech who is an expert on extremophiles in caves. Her view is that it's virtually impossible to rule out the possibility of earthly contamination just by looking at something in a rock sample, due to the ubiquity of life on Earth. Here's a sample quote:

"Rocks, even the most high density materials, are prone to microfractures. Microorganisms are notoriously splendid at working their way into incredibly minute microfractures. ...

"Showing that the bug that you have actually is NOT a contaminant organism that made its way into a meteorite is a practically unsolvable problem. If you turn up an organism whose chemistry, way of coding information, or something else (besides morphology) indicates that it is significantly (and I MEAN significantly) different from anything that has ever been seen on Earth, THEN you might have a chance of proving this. Pictures of tube shaped structures don’t do it."

Update for 2:40 p.m. ET: Carl Pilcher, director of the NASA Astrobiology Institute, told The Associated Press that the structures seen in the meteorite are most likely earthly contamination. He turned thumbs down on Hoover's claim that they were extraterrestrial organisms:

"There has been no one in the scientific community, certainly no one in the meteorite analysis community, that has supported these conclusions. The simplest explanation for Mr. Hoover's measurements is that he's measuring microbes from Earth. They're contamination."

Update for 4:45 p.m. ET: In a comment appended to Keith Cowing's posting about the study on NASA Watch, Rocco Mancinelli of the Bay Area Environmental Research Institute takes issue with the NASA statement that "the peer review process was not completed" when a paper by Hoover was submitted for publication in the International Journal of Astrobiology in 2007. "The paper was rejected, after peer review," said Mancinelli, who is listed as an associate editor of that journal. (Mancinelli also sent in critical comments that were included in my previous roundup on the "meteorite life" study.)

Update for 9:25 p.m. ET: There's been a lot of back and forth over whether Hoover has claimed to have a Ph.D. NASA Watch's Keith Cowing has put a lot of effort into this — and determined from NASA that he doesn't have a Ph.D., even though the Journal of Cosmology paper lists him as having one. Jennifer Lewter, a teacher who says she's a "big fan of Dr. Hoover's," indicates in her blog postings that he has two honorary doctorates.

Meanwhile, the journal's managing editor, Lana Tao, said in an e-mail that 21 commentaries on Hoover's paper had been received and that all were published, even though two (Nos. 11 and 15) still seemed to be missing at the end of the day. One of the late entries, from Oxford's Martin Brasier (No. 9) cast doubts on Hoover's results. "These samples have been sitting around in laboratories for between 205 and 73 years," he wrote. "It is well known that microbial contaminants can penetrate deep into such rocks, even during storage. The null hypothesis, therefore, is that many of these objects ... may be prokaryotic contaminants." (Cyanobacteria qualify as prokaryotic organisms.)

Tao also fired back once more at the journal's critics, insisting that Hoover's paper went through adequate peer review. Here's a quote from the e-mail:

"As every editor and guest editor will attest, all articles are subjected to peer review. We reject over 30 percent of invited papers and over 70 percent of those which are not invited. Every editor, and guest editor, has had their work subjected to peer review, and every editor has been required to revise their articles after peer review. Even the executive editors have been required to revise their papers after peer review.  We believe in peer review.

"Peer review provides wonderful feedback which can help make a paper better, or which can explain why the paper is hopeless and must be rejected. However, we do not reject great papers because we disagree with them as is the habit of other periodicals.

"Dr. Hoover's paper was received in November. It was subjected to repeated reviews and underwent one significant revision.

"We have published every commentary received, 21 so far. The vast majority support Dr. Hoover's findings.

"The choice is simple: Scientific discourse vs psychosis. Hysteria and lies do not constitute scientific doubt. They are calls for medication."

Update for 7 p.m. ET March 8: Now for the postmortems: Two more e-mails went out from Tao overnight. One was addressed to Paul Hertz, the NASA scientist who implied that the agency could not "stand behind or support" Hoover's claims because they had not been sufficiently peer-reviewed. In the message, which was copied to numerous others including yours truly, Tao said "we will file a formal complaint with NASA regarding your unprofessional, dishonest conduct." She said "over 30 NASA scientists have published with the Journal of Cosmology" and insisted that the articles "underwent rigorous peer review."

In another e-mail message, Tao thanked members of the media "for covering this important story and bringing attention to Richard Hoover's discoveries." She said the journal's owners accepted a buyout offer two weeks ago, before last weekend's flap. "The selling of JOC also means a new managing editor," she wrote. "Therefore with this thank you, I also get to say ... goodbye!"

Today, Columbia Journalism Review's Curtis Brainard recapped the whole saga of the microbes in the meteorite ... and the media ... in a posting to The Observatory blog.  "Anything having to do with extraterrestrials has a way of creating a media frenzy," Brainard observed. "But reporters have obviously learned from frenzies past."

I'm definitely feeling frenzied out, but Tao's earlier reference to Gil Levin's claims about the Viking experiments has reminded me to add that issue to the list of controversial astrobiology results:

• Did Viking find life on Mars ...
• ... Or did Viking kill life on Mars?
• Definition of life: Arsenic debate just won't die
• Strange find on Titan sparks chatter about life
• Mars methane mystery: What's making the gas?
• Meteorite study revives debate over life on Mars
• Search for alien life may take giant leap forward

Join the Cosmic Log community by clicking the "like" button on our Facebook page or by following msnbc.com science editor Alan Boyle as b0yle on Twitter. To learn more about Alan Boyle's book on Pluto and the search for planets, check out the website for "The Case for Pluto." 

R. Hoover / Journal of Cosmology

A field-emission scanning electron micrograph shows one of the filaments that was found in the Ivuna CI1 carbonaceous meteorite. The image includes labels for data about elemental composition. The bar at lower left shows the 1-micron scale. The filament looks similar to those seen in earthly cyanobacteria.

Last updated 4:20 p.m. ET March 6:

Are there traces of ancient bacteria trapped inside meteorites that fell to Earth decades ago? You can add that question to the list of unresolved issues surrounding the search for life beyond Earth, thanks to a just-published study by a NASA researcher.

The new study, published in the Journal of Cosmology, focuses on structures that look like the filaments that biologists typically see on micro-organisms known as cyanobacteria. Richard Hoover, an astrobiologist at NASA's Marshall Space Flight Center in Alabama, found the filamentary structures inside samples of meteorites that are thought to date back to the solar system's beginnings, more than 4 billion years ago.

If the structures are confirmed to be of biological but unearthly origin, that would serve as fresh evidence that life can make its way through outer space and "seed" planets, including our own, Hoover told me today.

"Life may have a wider planetary distribution than simply being limited to the planet Earth," he said. In the paper, Hoover said the evidence suggests that microbial life could well exist on comets or icy worlds such as Europa or Enceladus.

Most astrobiologists might be willing to go along with that broad conclusion. However, Hoover's specific claims could well end up in the same sort of limbo that surrounds the claims made 15 years ago about microfossils inside a meteorite from Mars.

The initial evidence was the subject of dramatic news conferences and huge headlines, but as time went on, doubts about the findings grew. Today, few astrobiologists see the Mars meteorite as containing any conclusive evidence for the existence of past or present Martian life.

Cautious and skeptical reactions
"This may turn out to be another one of those cases where it's controversial but remains unproven," Seth Shostak, senior astronomer at the California-based SETI Institute, told me today.

Shostak said Hoover's findings would be "important, if true." But he noted that the research paper relied on a highly technical interpretation of electron microscope images and chemical analyses. "Is it true? I'm not qualified to say that," Shostak said.

The Journal of Cosmology's editor-in-chief, Rudy Schild of the Harvard-Smithsonian Center for Astrophysics, said in a note accompanying Hoover's study that 100 experts were invited to critique the research, and that any commentaries would be published beginning Monday. The overall tone of the commentaries is likely to be skeptical: Lynn Rothschild, an astrobiologist at NASA's Ames Research Center in California, said many biologists were "very concerned" about the claims.

More than one expert wondered why the research merited any news coverage at all.

"Many scientists have examined thousands of meteorites in detail over the past 50 years without finding any evidence of fossil life," David Morrison, senior scientist at the NASA Astrobiology Institute at Ames Research Center, told me in an e-mail. "Further, we know a great deal about the conditions on the parent objects of the meteorites, which (not counting the few meteorites from the moon and Mars) were rather small, not at all like planets.

"I would therefore invoke Carl Sagan's famous advice that extraordinary claims require extraordinary evidence. At a bare minimum this would require publication in a prestigious peer-refereed scientific journal — which this is not. Cyanobacteria on a small airless world sounds like a joke. Perhaps the publication came out too soon; more appropriate would have been on April 1," Morrison said.

Questions about origin
The debate over the validity of Hoover's claims is likely to concentrate over whether the filamentary structures are truly biological in origin, and if so, whether they're the result of earthly contamination.

Hoover said that the filaments, which can measure more than 20 microns long, are of the right size and shape to match the characteristic structures seen in types of cyanobacteria.

"Because of the fact that they are so large and so complex, and many of them have specialized cells, these cyanobacteria can be identified — sometimes to genus and species — just on the basis of certain specialzed cells," he explained. One of the structures found in the meteorites is similar to that seen in the giant bacterium known as Titanospirillum velox, for example.

If the structures are so similar to those seen in earthly organisms, could that be because they're actually the traces of cyanobacteria that found their way into the meteorite? Hoover argues that they're not the result of contamination. He said that cyanobacteria are generally found in aquatic environments, but the meteorites are made of stuff that falls apart when exposed to liquid water. He also said chemical tests on the filaments could find no evidence of nitrogen, which should have been present if earthly cyanobacteria infiltrated the meteorites. One of the meteorites, for example, is known to have fallen to Earth in France in 1864.

"The inability to detect nitrogen in the filaments indicates that they are ancient, and since the meteorite came to Earth in 1864, that indicates that they were in the meteorite when it fell," Hoover said.

Previous analyses of the meteorites' chemical composition have concluded that they were formed during the solar system's earliest epoch, perhaps as comets. But Hoover said that doesn't necessarily mean the structures were present from the very beginning. They could have been picked up from debris that was knocked into space by cosmic impacts. They could even have come from Earth itself, as the result of a meteor blast that occurred millions or billions of years ago.

"That's absolutely possible," Hoover acknowledged. "I have no reason to say I could rule that out."

Hoover has made provocative claims before, and he fully expects that others will contest his conclusions this time as well. "I can only make my observations, based on the scientific results that I see," he told me.

What do you think? Is this a significant advance for the study of life beyond Earth, or a blip hardly worth writing about? Feel free to weigh in with your comments below.

Update for 6 p.m. ET: Rocco Mancinelli, senior research scientist at the Bay Area Environmental Research Institute, weighed in with this e-mailed critique of Hoover's paper:

"As a microbiologist who has looked at thousands of microbes through a microscope, and done some of my own electron microscopy, I see no convincing evidence that these particles are of biological origin.  

"The techniques used may not have been appropriate for these types of analyses. It is stated that the implements were flame-sterilized, with no details of how this was performed.  Were the implements placed in the flame of a Bunsen burner? If so, sometimes soot can get on them at the microscopic level. The usual procedure for flame sterilization is to dip the implements in ethanol then burn the ethanol off. Yet, these would be inappropriate for this type of analysis. You need to have everything clean and then bake at 550 degrees C overnight.  These missing details would cause me to question not just about the photos, but the elemental analyses as well.  I am also disturbed about the lack of nitrogen. There should be more. There are many technical flaws in this paper."

Update for 10:50 p.m. ET: Dale Andersen, principal investigator at the Carl Sagan Center for the Study of Life in the Universe at the SETI Institute, sent his detailed reaction in an e-mail:

"I would be absolutely thrilled to see this story verified, and it would be even more exciting if we found evidence of life that was quite different from terrestrial life — say, for example, its genetic coding used different base pairs than Earth life. That would imply not just evidence of life from beyond our planet, but would demonstrate an independent genesis of life, something that would be absolutely astonishing.

"That said, one needs to look at this paper with a lot of caution, particularly with [the Mars meteorite] ALH 84001 in mind. That was a great story and generated a wonderful debate that continues even today — regardless of the outcome, I would say it was a success story. The best of the best have worked on that meteorite and tried in vain to prove or disprove the original thesis that ALH 84001 holds evidence of life from the planet Mars. While I think it's fair to say that the general scientific consensus is that McKay et al. [the researchers who did the Mars meteorite study] did not provide unambiguous evidence of extraterrestrial life, the process that accompanied the effort throughout was well worth the effort. The scientific community was compelled to think in new ways and to find better tools and methods to examine the evidence. This resulted in technological advances and a much better understanding of how to approach the problem and finding its answer. And the public was very engaged throughout, which was a good thing. I hope there is long-term, strong support for NASA's Exobiology program and that NASA is allowed to continue the search for a better understanding of the origin, evolution and distribution of life in the universe; it's a goal worthy of support.

"With respect to Richard Hoover's claims about finding evidence of life within the samples of meteorites he has observed, I think he has a very high bar to clear before this story is accepted by the scientific community.  It should also be noted that Richard has published this thesis previously (e.g., in 2004: "Perspectives in Astrobiology" (NATO Science Series: Life and Behavioural Sciences, Vol. 366) [Hardcover] Richard B. Hoover (Editor), Aleksei Iurevich Rozanov (Editor), Roland Paepe (Editor)), and the ideas were not well-received nor did they gain traction within the scientific community.

"Peer review will include the examination of his and other scientists’ data and logic, and not until that has occurred will we see how the story unfolds. Occam's razor will eventually be used to slice and dice the carbonaceous chondrites used by Richard to present his evidence. Is it more likely that upon looking into the interior of a meteorite collected on Earth and finding photosynthetic cyanobacteria, which on Earth are usually found in water or wet sediments, their presence is due to contamination from terrestrial sources or that it formed inside the parent body of comet or asteroid in deep space? There will be many other possibilities to rule out before one arrives at the extraterrestrial answer.

"I hope the public does not assume that this story is a certainty — it clearly is not, at least not at this point.  Mostly, I hope the general public is able to learn more about the scientific process and the use of critical thinking skills to arrive at the truth and are not confused by an endless parade of silly articles that neither enlighten nor inform. Let the debate begin.

"A side note: I am not an expert with respect to meteorites. It would be very useful to get some of the ALH 84001 folks to weigh in on Richard’s findings, techniques, histories of the meteorites used (where collected, handling), logic etc. And while it may be OK to express healthy skepticism in public forums — meetings such as AbSciCon, AGU, AAAS, etc. and the scientific literature are the places to really rebut and critique the body of work presented — the scientific process should be the judge. Perhaps that is the real story here.  Let the facts demonstrate the truth."

I e-mailed an inquiry to David McKay, one of the leaders of the ALH 84001 research team at NASA's Johnson Space Center, even before Andersen mentioned the idea — and I'll report back if I hear anything.

Update for 3 p.m. ET March 6: More critical commentaries are coming in, from Pharyngula's P.Z. Myers as well as from Rosie Redfield, the microbiologist at the University of British Columbia who blew the whistle as well on the "arsenic life" research that made such a splash last December. Here's a link roundup:

• Pharyngula: Did scientists discover bacteria in meteorites?
• RRResearch: Is this claim of bacteria in meteorite any better than 1996's?
• NASA Watch: MSFC astrobiologist claims he's found life in a meteorite
• Dot Earth at N.Y. Times: NASA scientist sees signs of life in meteorites
• NPR: Has evidence of alien life been found in meteorites?
• Discovery News: Has evidence for alien life been found?
• Bad Astronomy: Has life been found in a meteorite?

Update for 4:20 p.m. ET March 6: Rudy Schild, the astrophysicist at the Harvard-Smithsonian Center for Astrophysics who is also the editor-in-chief of the Journal of Cosmology, sent this open letter via e-mail today:

"The Journal of Cosmology had issued a personal invitation to 100 scientists, and a general invitation to over 5,000 members of the scientific community, inviting critical commentary on Dr. Hoover's landmark, paradigm shattering paper.  All were given access to a PDF containing a preprint of Dr. Hoover's article.

"Within hours of making it available, it was downloaded over 1,400 times.

"After issuing an open invitation for scientists to search for flaws and to report them in a scientific forum, as of March 6, the Journal of Cosmology has received 12 commentaries.

"Five detail what could best be described as minor quibbles. One offers an alternative explanation as to the origin of these fossils but does not dispute the evidence. We will publish all commentaries so far received, this evening.

"It is natural to have doubt. Skepticism is the nature of science. Debate is healthy and is good for science. We are frankly amazed that we have not received an avalanche of critical commentaries.

"Perhaps the reaction could be described as 'stunned silence'?

"As to those who post insults on various websites, this is not to be taken seriously.

"On the other hand, Dr. Hoover's article, and the lack of scholarly, critical dispute, may be an indication of a paradigm shift; similar to the realization that Earth was not flat nor the center of the Universe. What I mean is: Most scientists and perhaps most of the public realize life must be everywhere throughout the cosmos and not just confined to Earth, and Dr. Hoover's paper simply confirms what most already suspect.

"This may also account for why the over 150 news articles and blogs so far published (with the exception of MSNBC), the response has been generally favorable or positive in nature.

"The inability, so far, of the scientific community to find and present any major flaws in a scientific forum and to submit and publish them in a scientific Journal which has invited critical commentary, speaks for itself.

"However, the jury is still out.  Our deadline for receipt of scientific commentaries is Monday, the 7th.   We will extend that deadline.

"The Journal of Cosmology will publish critical commentary. We encourage it. We ask the media to encourage the scientific community to send us critical commentary.

"However, so far, the verdict appears to be: We are not alone."

Earlier, Schild forwarded some additional reactions to Hoover's paper. Here is a quote attributed to Carl Gibson of the Center for Astrophysics and Space Sciences at Scripps Institute and the University of California at San Diego:

"Dr. Hoover has provided the world with extraordinary evidence to back up extraordinary claims. This discovery completely changes our perspective of the nature of life and our place in the universe. The world will never be the same."

Here's a quote from Chandra Wickramasinghe, director of the Astrobiology Centre at Cardiff University, who has also stirred up controversy for his views about life from space:

" Dr. Hoover has provided the world with decisive evidence that we are all aliens. Life is a truly cosmic phenomenon. ... We believe Dr. Hoover's evidence, coupled with other findings and recent genetic studies, indicates life has a genetic ancestry which leads over 10 billion years back in time. Some of these life forms were delivered to Earth, in comets."

I've started up a new item with further reaction, from the Journal of Cosmology's commentaries as well as other sources. 

More controversies in astrobiology:

• Definition of life: Arsenic debate just won't die
• Strange find on Titan sparks chatter about life
• Mars methane mystery: What's making the gas?
• Meteorite study revives debate over life on Mars
• Search for alien life may take giant leap forward

Join the Cosmic Log community by clicking the "like" button on our Facebook page or by following msnbc.com science editor Alan Boyle as b0yle on Twitter. To learn more about Alan Boyle's book on Pluto and the search for planets, check out the website for "The Case for Pluto."