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.

Henry Bortman / 2010

Astrobiology researcher Felisa Wolfe-Simon works with samples at California's Mono Lake.

Last updated 8:30 p.m. ET

After five months of battles in the blogosphere, the debate over whether life can be based on an alternate biochemistry is playing out on the highest levels of peer-reviewed research.

Back in December, the journal Science sparked a ruckus by publishing an online report from researchers who claimed that they had coaxed bacteria from California's Mono Lake to live on arsenic rather than phosphorus. That's a big deal, because phosphorus is thought to be one of the six elements essential for life as we know it (along with carbon, hydrogen, nitrogen, oxygen and sulfur). Arsenic, on the other hand, is typically seen as a potent poison.

The researchers, led by astrobiologist Felisa Wolfe-Simon at the U.S. Geological Survey, suggested that such an alien biology could exist in environments beyond Earth that are traditionally thought to be inimical to life — for example, the hydrocarbon seas of Titan, Saturn's largest moon.

That sounds like a wonderful vision, but the claims from Wolfe-Simon and her team instantly came under attack from other chemists and microbiologists. In a flurry of blog postings and Twitter tweets, the critics took aim at what they saw were fatal flaws in the team's methodology. Wolfe-Simon and her colleagues defended their work in a Q&A issued via Science, but said they preferred to pursue the debate through the traditional peer-review process.

Now that process has taken a great leap forward. Today Science posted eight peer-reviewed technical comments from the critics to its Web site, along with a response from the original research group. The journal said all these papers would be printed, along with the original study (which has so far been available only online), in next week's edition.

"There's a lot of stuff that's happened," Wolfe-Simon told me today. "It's been a real challenge for me and my co-authors. ... We think this is evidence that, really, science is moving forward faster."

She held to the original claim that molecules of arsenic were incorporated into the machinery of life, replacing at least some of phosphorus. "We would argue that our conclusion is still viable," she said. "We never claimed 100 percent substitution, and in a way that point was misconstrued."

Wolfe-Simon said more evidence has been amassed to back up the arsenic-life claims over the past five months. However, the fresh evidence had to be held back for future publication. Wolfe-Simon said she was constrained from reporting new data in today's online response to the critics, which was a source of frustration for her. Science insisted on that to keep the cycle of response and counter-response from spinning out of control.

It's not unheard of to publish technical comments and responses in the wake of a controversial paper. Science did exactly that this week, with regard to a study claiming that microbes consumed all the methane that leaked from last year's Deepwater Horizon spill in the Gulf of Mexico. But it's very unusual to publish a research paper, eight critiques of that paper and a follow-up response to those critiques in the same issue of a scientific journal.

Science's editors said they did not expect their data dump "to be the final word on the subject."

"The fact that we received so much feedback to the Wolfe-Simon paper suggests to us that science is proceeding as it should," the editors said in a statement. "The study involved multiple techniques and lines of evidence, and the authors felt their conclusion was the most plausible explanation for these results when considered as a whole. We hope that the study and the subsequent exchange being published today will stimulate further experments — whether they support or overturn this conclusion."

The criticisms — and the responses from Wolfe-Simon and her colleagues — thus set the ground rules for the debate, which will likely continue for months and years to come. Here's a quick rundown of some of the issues involved:

Criticism: The "arsenic-eating" bacteria, known as GFAJ-1, were grown under conditions that still had trace amounts of phosphorus, and it's more likely that the microbes used that trace phosphorus rather than the arsenic. The arsenic-life researchers claimed there was so little phosphorus left that the bacteria couldn't possibly have survived on it — but under extreme conditions, some individual microbes have been found to survive on that little.  

Response from the team: They point out that they checked bacteria under three conditions: high phosphorus and low arsenic; high arsenic and low phosphorus; low arsenic and low phosphorus. If the "arsenic-eating" bacteria were actually living off the low levels of phosphorus, they should have done as well in the low-arsenic / low-phosphorus environment. But they didn't. The team also says the survival rate on an ultra-low-phosphorus level should be compared based on wider populations, and not based on individual extremophile microbes.

Criticism: In the course of breeding bacteria to make them live in a high-arsenic environment, the team might have actually created bacteria that adapted to the low-phosphorus concentrations by processing the chemicals differently. That would explain why the high-arsenic / low-phosphorus bacteria did so much better than the low-arsenic / low-phosphorus bacteria.

Response from the team: They saw no evidence that the bacteria's biochemistry processed phosphorus in the way that was suggested, but acknowledged that the chemical pathways used by GFAJ-1 "are important avenues for future investigation."

Criticism: The molecular bonds involving arsenic would simply not be strong enough to hold up in alternate forms of DNA and other biochemical building blocks. What's more, phosphorus is far more abundant than arsenic in the solar system, and most of the arsenic available on rocky planets would be available in a form that is structurally quite different from phosphorus. These considerations point to the unlikelihood of life arising on Earth or elsewhere with an arsenic-based biochemistry.

Response from the team: It's conceivable that the arsenic bonds in large biomolecules are more resistant to a breakdown than the bonds in smaller molecules. "GFAJ-1 may have evolved specific strategies to cope with this issue, such as stabilizing structures," the team wrote.

Criticism: The team didn't devote enough attention to guarding against contamination of their samples and purifying the DNA that they analyzed. What's more, the uncertainties surrounding the measurements may not allow the team to make definite conclusions.

Response from the team: Wolfe-Simon and her colleagues recap the procedures they used and say they "were sufficient to remove any impurities." They also cite multiple techniques that cross-checked their results, through radiolabeling as well as high-resolution mass spectroscopy. They agree that further analysis of the DNA "would be a useful future experiment" because it could shed further light on the chemistry involved. They reworked their calculations on some of the analysis to respond to some of the criticisms about averaging, and said the data still supported their conclusions.

The bottom line is that the debate will continue, with more researchers getting into the act. Wolfe-Simon's team says samples of GFAJ-1 are being made available to other labs upon request, through the Oremland Laboratory at the U.S. Geological Survey.

"We look forward to working with our peers to replicate our observations and to test our hypotheses along the lines suggested by [one of the critics, Stefan] Oehler and others," the team writes.

One of the most vocal critics, University of British Columbia microbiologist Rosie Redfield, said today that she was still unconvinced:

"The authors don't report any new experiments. Most of their responses take the form of 'our interpretation could be correct on this point if...' In many cases there is indeed a small possibility that it could, but there are so many of these points of interpretation, each with only a very small probability of being correct, that I don't think anyone will find the arguments convincing."

Redfield said the team's responses to her comments about contamination were "in some ways the most scientifically valid, as they provide information about their media and DNA purification." She promised to have more about that on her blog later today.

So the blogosphere beat goes on. What do you think? Are you intrigued by this latest chapter in the grand scientific debate, or has the whole subject of arsenic life lost its appeal? Either way, please feel free to add your comments below.

Update for 8:30 p.m. ET: I've added some comments from Wolfe-Simon above after chatting with her this afternoon. She said she and her colleagues took Redfield's concerns about potential contamination very seriously. "Her criticisms are definitely valid," she said. "One of the first things we went back and did was look at all the ways we can get [phosphorus levels] down to zero."

But she said the key observations would come when scientists look at GFAJ-1's molecular machinery, to confirm that arsenic really is being incorporated into DNA, lipids and other molecules where phosphorus is usually found. "The question that people are really asking is, 'Show me the money. Let's see those biomolecules,'" she said.

Wolfe-Simon said she and her co-authors have been getting offers of help from other researchers in fields ranging from molecular biology to astronomy. She's also been getting supportive messages from lots of folks, including a 7-year-old girl who told her she wants to do research at Mono Lake when she grows up. "If I can put my peg on the wall, if we can ask the right questions ... she's going to answer the questions," Wolfe-Simon said.

Meanwhile, Redfield has posted an additional blog item that details her concerns about contamination. She's not satisfied with the response that Wolfe-Simon and her colleagues provided. "Overall, the most striking aspect of the authors' formal response is that they never admit to having made any mistakes or having done anything badly," she writes. "This is a bit disconcerting, given how many concerns were raised."

Update for 9:30 p.m. ET: An additional post from Rosie Redfield addresses how to test arsenic-life claims. Meanwhile, science writer Carl Zimmer looks at the big role that online discussion played in the arsenic-life debate, and Nature's Erika Check Hayden rounds up reactions from other researchers. One theme: Is it worth spending time and effort to try replicating the findings?

The story so far:

• December 2010: Life as we don't know it ... on Earth?
• 'Weird life' claims spark a backlash
• 'Weird life' reveals science at work
• 'Weird life' researchers answer critics
• February 2011: Arsenic debate just won't die
• April 2011: Alien life revisited

Science is making all 10 papers accessible with free online registration. You can see the whole list on Science Express, the journal's rapid-publication website, and here's an item-by-item menu:

• Comment by James Cotner and Edward Hall
• Comment by Rosemary Redfield
• Comment by B. Schoepp-Cothenet, W. Nitschke, L.M. Barge, A. Ponce, M.J. Russell and A.I. Tsapin
• Comment by Istvan Csabai and Eors Szathmary
• Comment by Stefan Oehler
• Comment by David Borhani
• Comment by Steven Benner
• Comment by Patricia Foster
• Response by Felisa Wolfe-Simon, Jodi Switzer Blum, Thomas Kulp, Gwyneth Gordon, Shelley Hoeft, Jennifer Pett-Ridge, John Stolz, Samuel Webb, Peter Weber, Paul Davies, Ariel Anbar and Ronald Oremland
• "A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus" by Felisa Wolfe-Simon et al.

You can connect with the Cosmic Log community by "liking" the log's Facebook page or following @b0yle on Twitter. Also, give a look to  "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."

C. Carr

This 1 inch by 1 inch microfluidic chip is part of the SETG instrument prototype. Tiny channels feed in the samples to be analyzed and control the fluidic circuitry on the chip. Blue light excites fluorescent dyes that help identify DNA within 3072 cubic chambers, each about the width of a human hair, or one billionth of a liter in size.

Life as we know it has a common ancestor — somewhere. Is it a Martian? A new device under development to fly on a future mission to Mars to find and sequence bits of genetic material could provide an answer, according to MIT and Harvard scientists.

"Given what we know about meteorite impacts and transfer of material between Earth and Mars, we are hoping that life may in fact exist on Mars and that it may in fact be related to us," Christopher Carr, a MIT research scientist who is leading the project, told me today.

The idea that life originated on Mars goes back before the Viking missions of the 1970s, which looked for signs of life on the Red Planet. It got a boost in the 1990s with the discovery that microbes could have hitched interplanetary rides on meteorites between the two planets during an intense period of bombardment between about 3.5 and 4 billion years ago.

"About a billion tons of rock probably went between Earth and Mars, most of that actually went in the Mars-to-Earth direction — about a 100-fold higher amount," Carr noted. "So that makes it more likely that if we find something on Mars that's related to us that it actually came from Mars to Earth."

Device development
Carr and colleagues have identified regions of genome sequences that are conserved across all known life forms on Earth and are working on a device that will look for bits of this genetic material on Mars.

The device, called the Search for Extra-Terrestrial Genome (SETG), will isolate any RNA or DNA from bits of soil, rock and ice brought up from the subsurface of Mars, amplify it to the point it could be detected and then sequence it.

So far their prototype consists of the micro-fluidic chip in the image above which can amplify and detect bits of genetic material. In the next few years, they aim to add components to isolate the genetic material and sequence it as well.

"Our hope is that in the next two years, we will have a system that we can put in soil at the beginning and get sequences out at the end," he said. The aim is for an instrument that weighs about 2 kilograms and is roughly the size of a shoebox.

Finding genetic material on Mars that shows a link with life on Earth would allow scientists to learn more about how we are related and when the split occurred. As for whether the scientists will have any luck finding genetic material that shows we're all Martians remains an open question.

"I think it is entirely possible," Carr said. "I wouldn't necessarily say probable. Bottom line, if it is there, we want to find it. It may or may not be."

More stories about life on Mars:

• Did probes find Martian life … or kill it off?
• Were life's building blocks picked up on Mars decades ago?
• Next up for Mars missions: the search for life
• Early cave bacteria hints at Mars life

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." 

Henry Bortman

Astrobiology researcher Felisa Wolfe-Simon works with samples at California's Mono Lake.

The continuing controversy surrounding the announcement of strange bacteria deep in a California lake that can apparently survive on arsenic and even incorporate the element into its DNA is being held up as a shining example for how the scientific process works.

The latest to point this out are the folks at Real Climate, a blog on climate science — a discipline that is no stranger to controversy.

The arsenic-DNA study, published in the journal Science, was announced at a NASA news conference on Dec. 2 that was hyped in advance as an opportunity "to discuss an astrobiology finding that will impact the search for evidence of extraterrestrial life."

What's groundbreaking about the find is it suggested that salt-loving bacteria gathered from California's Mono Lake could be coaxed to substitute atoms of arsenic, which is toxic to life on Earth, in place of the usual phosphorus atoms in DNA and other parts of their cellular machinery.

If that's possible on Earth, then it's also possible that such alternate forms of life could be thriving elsewhere in the universe. This, in turn, might expand the definition of "life" and require a broadened search for extraterrestrial organisms.

Since the study was published, a number of microbiologists and chemists have questioned whether the experiments actually proved the researchers' point.

Among their criticisms are concerns that inadequate care was taken in purifying DNA samples from the bacteria in the arsenic-rich medium, and that the arsenic found in the DNA was merely contamination. They said that the bacteria might have been using trace amounts of phosphorus left as impurities in the growth medium.

As these criticisms played out in the media and on the Internet, the researchers behind the original paper issued a statement responding to their critics — and said more would be forthcoming in Science.

So that's the story so far. Has this high-profile airing of claims, counterclaims and counter-counterclaims hurt the credibility of the scientists involved? Not at all, Real Climate's bloggers say. Instead, they contend that the controversy "has demonstrated the credibility of scientists, and should promote public confidence in the scientific establishment."

Climate scientists are keen to point out the scientific process at work, in part to counter their own critics. Such critics say many researchers are afraid to go against the scientific consensus that human activity is a driving factor in global climate change because it might staunch their flow of funding from agencies such as NASA.

Real Climate flagged a comment on the Watts Up With That blog, a hub of climate skeptics, that reads:

"It’s amazing how fast the scientific community came out to attack NASA for what they claim is plainly flawed science. Then again, NASA isn’t funding any of the attackers.

"In the Climategate mess, however, we still have heard very little from an awful lot of so-called scientists who should have been saying a lot more about flawed science but are too afraid to lose their grant money."

The reality is more complex: Science writer Carl Zimmer has done the work to show that many of the arsenic-DNA study's critics are indeed NASA-funded, including Norman Pace at the University of Colorado, extremophile expert Hazel Barton at the University of Northern Kentucky, and John Roth at the University of California at Davis.

Real Climate notes: "Scientists offer opinions based on their scientific knowledge and a critical interpretation of data. Scientists willingly critique what they think might be flawed or unsubstantiated science, because their credibility — not their funding — is on the line."

While the Real Climate bloggers have mixed feelings about the arsenic-DNA controversy playing out in the blogosphere and media, rather than strictly within the confines of the peer-review process, they are far from alone in using the controversy to help explain the merits of the scientific process.

Over on the NeuroLogica Blog, for example, Steven Novella has a post up that responds to a comment on the ScienceNOW website in which the criticism is characterized as "unfair."

"The commenter is confusing being fair with being nice. The self-critical aspect of science is not nice. It’s brutal – necessarily so. But it is still fair and professional, just not politically correct.

"This is one critical aspect of science that I feel the public needs to better appreciate. This is also a fun and dramatic aspect of science — real-world mud fights where scientists go at each other’s throats. The mass media needs to appreciate this real drama more so that they will rely on their hackneyed Hollywood cartoon of science less."

In USA Today, science columnist Dan Vergano recaps the controversy and notes that the back-and-forth is likely to continue, though it will eventually be settled via the peer-review process.

What do you think about the way in which the "weird life" controversy has been playing out on blogs and in the media, rather than strictly through the peer-review process? Is it actually a shining example of science at work? Feel free to weigh in with your comments below.

John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).