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

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