Langbahn Team – Weltmeisterschaft

Talk:Allan Hills 84001

The annoucement of the ALH84001

The annoucement of the ALH84001 was first made by a NASA Press Release August, 7th 1996 with later statements of President Bill Clinton. The article in Science published August, 16th.

See Press Release from NASA at ftp://ftp.hq.nasa.gov/pub/pao/pressrel/1996/96-160.txt See Press Release from White House at http://clinton6.nara.gov/1996/08/1996-08-07-remarks-by-president-upon-departure.html See McKay, D. S. & Gibson Jr., E. K. (1996). Search for past life on Mars: Possible relic biogenic activity in Martian meteorite ALH84001. Science 273(5277): 924-931.

All of the facts included in this page are true, with the exception that it could not be confirmed to any reliable degree using radio-carbon 14 dating, since it is far too old. I would propose removing the reference to this test, since it doesn't apply to any object whose supposed arrival on earth was far past the acceptable threshhold of RC-14 dating.

Exogenesis

Is the comment about the word "Exogenesis" really necessary? It just redirects to the Panspermia article. Count Zero 08:48, 7 May 2006 (UTC)[reply]

The last two links in the External Link category do not work.

Opinion or Fact?

The article states that "most experts agree", and somewhat later cites a reference from the Associated Press that the finding has been discredited. References should be from either scientific sources or from published surveys so that we do not have to simply trust that "most experts agree"... (I know a number of experts who do Not agree).

Moreover, nanobacteria have not been discredited; to the contrary, the evidence is growing that they do indeed exist. See for example the Wikipedia article on Nanobacterium, particularly the findings in 2005-2006 Nanobacterium. Bonnie108 17:46, 5 April 2007 (UTC)[reply]

Wow, you know a number of "experts" who do not agree? I'm impressed.65.7.5.159 (talk) 04:40, 14 December 2012 (UTC)[reply]

Name

ALH84001 → ALH 84001 — The official abbreviation for this meteorite is ALH 84001 and it is equally common. — Basilicofresco (talk) 19:46, 16 June 2008 (UTC)[reply]

I suggest to move it... is there any comment? Basilicofresco (talk) 13:34, 7 July 2008 (UTC)[reply]
why use an abbreviation. The real name is Allan Hills 84001--JeffG (talk) 22:15, 7 July 2008 (UTC)[reply]
Well, because it is more common the abbreviated form than the full name. However I have no objection for the use of the full official name. In my opinion the point is to use an official denomination. Basilicofresco (talk) 05:11, 8 July 2008 (UTC)[reply]
I strongly recommend using the full, formal name on the article, and making sure that the abbreviation, with and without the space, redirects there. The policy for using abbreviations in titles says it must be "almost exclusively known only by its acronym and is widely known and used in that form." This name fails the exclusive test and is not an acronym. --JeffG (talk) 17:55, 8 July 2008 (UTC)[reply]
I absolutely believe that the title should go back to ALH 84001. It's absolutely more well known: Google has 24,200 hits for ALH 84001, but only 7,070 for Allan Hills 84001, and I've only ever seen it as ALH 84001 in publications before. Kuralyov (talk) 06:28, 23 November 2008 (UTC)[reply]
Nobody would argue that it isn't better known by its abbreviation. However, you are not correct about its use in publications: there are many that use the formal name. This is simply not a case where it is "almost exclusively" known by the abbreviation. You prove this with the google statistics, which show a quarter of the hits using the formal name (about the same ratio as in publications). Contrast this with something like "NASA" or "BBC", where at most a few percent of google hits use the formal name. Finally, the Guidelines for Meteorite Nomenclature, published by the Meteoritical Society, say that correct usage is to write the full names of meteorites in titles [1]. We should try to do it correctly here too. JeffG (talk) 14:37, 23 November 2008 (UTC)[reply]

Legibility

"Around 1 in 10 million meteorites from Mars arrives in less than a year, and around 10 rocks that weigh more than 100 grams make the journey in 2-3 years." Can someone please rewrite this sentence so that it makes sense? --Golbez (talk) 02:50, 28 September 2008 (UTC)[reply]

Confusing text

This section seems muddled to me:

Several tests for organic material have been performed on the meteorite and amino acids and polycyclic aromatic hydrocarbons (PAH) have been found. The debate if the organic molecules were created by nonbiological processes or are due to contamination from the contact with Antarctic ice is still ongoing.

What about the debate that they were created by biological processes on Mars? That seems to be the main point of interest, and it's not even mentioned.

As of 2006, some experts still argue that the microfossils are not indicative of life, but instead are caused by contamination by earthly biofilms.

"Some experts still" sounds like a dwindling minority view. So, the majority view is that the microfossils are indicative of life, and, by implication, life on Mars? Is that really true? If so, it needs to be clearly stated. If not then the wording needs adjusting to avoid the implication.

Nevertheless, evidence continues to grow that nanobacteria do exist, in spite of initial skepticism[10] (based on the idea that the particles were too small to contain RNA).

Does this mean nanobacteria on Mars, or on Earth? —Preceding unsigned comment added by 86.136.26.202 (talk) 01:58, 16 November 2009 (UTC)[reply]

"new secrets of possible life"

There is a new news release today on new data obtained from this meteorite. Here it is for those interested in incorporating its info into this article: [2]. The document is part of the November issue of the journal Geochimica et Cosmochimica Acta, the journal of the Geochemical and Meteoritic Society. Its authors are Kathie Thomas-Keprta, Simon Clement, David McKay, Everett Gibson and Susan Wentworth. -65.207.116.226 (talk) 18:00, 25 November 2009 (UTC)[reply]

Removed OR

I removed the following section:

Recent studies on ALH 84001 have shown that, although chances are low, eventually, Martian rocks such as ALH 84001 could actually transfer Martian life to Earth.[1] Bacterial spores, and rock dwelling organisms are speculated to survive in space for 5 years, meaning transfer of Martian life to our planet is theoretically possible.
If Mars's atmosphere at the time life started on Earth was like it is now, though, survival and propagation of any life form after arriving would be even less likely. The life form's native environment probably would be completely unlike anywhere it would land on Earth. Mars has an atmosphere many times thinner than that on top of Mount Everest, with almost no water. A life form evolved to survive in such conditions would almost invariably find dense air to be toxic, as it would the relatively high temperatures[citation needed]: even the Antarctic does not get as cold as much of Mars does most of the year.[2]

References

  1. ^ Paine, Michael (October 1996). "Transpermia - microbes hitch a ride between planets". Retrieved 2008-03-21.
  2. ^ :: NASA Quest > Aerospace ::

Age estimate

The age estimate of this rock has been revised down to 4.091 billion years, based upon lutetium-hafnium isotope analysis.[3]—RJH (talk) 19:58, 16 April 2010 (UTC)[reply]

This appears to be in conflict with the claim, later in the same paragraph, that the rock was blasted off the surface of Mars 4.5 billion years ago. — Preceding unsigned comment added by Dirtgirl (talk • contribs) 14:49, 24 July 2014 (UTC)[reply]

Nanobacteria

From the article:

Furthermore, microbiologists have successfully cultured nanobacteria in the lab, with sizes within the range of at least some of the purported microfossils in ALH 84001.<ref>http://www.agu.org/sci_soc/eisromanek.html</ref>

The link (http://www.agu.org/sci_soc/eisromanek.html) does not work for me. The nanobacterium article calls into doubt the idea that nanobacteria are living organisms. --JWSchmidt (talk) 23:54, 11 December 2010 (UTC)[reply]

False Reference

6 paragraphs down in the "Possible biogenic features section" says "Other initial skepticism towards the biogenic hypothesis focused on the idea that the nanometer-sized filaments were too small to contain RNA, but evidence continues to grow that nanobacteria do exist in nature.[14]" However, the actual reference concludes the exact opposite of that, stating that samples thought to be of nanbacterial origin are in fact derived from host cells, and "all fail to provide reasonable support for the existence of small microorganisms referred to as nanobacteria." —Preceding unsigned comment added by 216.227.89.35 (talk) 17:53, 7 April 2011 (UTC)[reply]

Photograph scale

I assume the cube with 'N1' written on it next to the meteorite is there for scale - but what scale is it? Is it 1cm3? Could it be clarified in the caption please? 86.138.46.156 (talk) 10:06, 6 August 2011 (UTC)[reply]

Magnetite grains

Why no mention of the magnetite grains? As I recall, these were central to the debate over whether there was evidence of life in the meteorite. --Amble (talk) 22:01, 7 September 2012 (UTC)[reply]

I agree, and so does Dr. Guy Consolmagno, now director of the Vatican Observatory. (Or he at least agreed in 2000, at the very end of Part 1 of his book, "Brother Astronomer.") Paraphrasing his comments, he noted that most of the press attention went to the worm-like structures, which he considered the weakest of the evidence. He said we know of no way to produce magnetite crystals of that purity, size, structure, and consistency except in bacteria. Either nature is more clever at making them than we think, he concluded, or they are terrestrial contamination, or they were made by Mars bugs. But he concludes, to accept the latter, you have to throw out all sorts of ideas about planetary chemistry and the origins of biology. Therefore, it's going to take a "complex suite of evidence and theory" for the proposition to be accepted. 121.163.188.1 (talk) 08:50, 2 August 2016 (UTC)[reply]

You could write it into the article. The source sounds reliable, and if you have the book on hand, you'd be eminently suited to adding it yourself. Banedon (talk) 09:06, 2 August 2016 (UTC)[reply]
A a good point to mention, since McKay was involved, but keep unbiased. The experiments, observations and models (reported here) ruled out contamination; the magnetite was incorporated during rock formation from an outside source and it excludes inorganic synthesis by heat alone; but it does not "prove" biogenic origin. Cheers, BatteryIncluded (talk) 17:59, 2 August 2016 (UTC)[reply]

Neutrality

Currently the section on "possible biogenic features" reads strongly pro-life. In particular the reference [1] is strongly against the detection of life (just check out the title: "few believe life on Mars"), yet the citation to it in the section quotes only David McKay's pro-life statement. Considering the wealth of contrary information in the citation, some very detailed, I think this is a blatant breach of neutrality. As such I've added a NPOV tag. Banedon (talk) 02:52, 12 September 2012 (UTC)[reply]

That's strange, because I also see neutrality problems with this section, but for the exact opposite reason.--Jacob.husted (talk) 17:53, 2 October 2012 (UTC)[reply]

From what I've read elsewhere, I thought this whole "nanobacteria" idea had now been consigned to the dustbin of science... 86.146.106.216 (talk) 20:58, 8 November 2012 (UTC)[reply]
Dear 86.146.106.216 (talk) Esq.,
"(...) From what I've read elsewhere (...)", IMHO, doesn't cite clear sources.
As well, AFAIC, there is no such thing as a "dustbin of science".
Please compare the "Falsifiability", "Demarcation problem" and the "Consensus reality" articles.
Thanks for reading me.
  M aurice   Carbonaro  08:40, 10 January 2013 (UTC)[reply]
I have done a general edit of this section addressing the neutrality issue. In addition, I'd like to delete the "Student participation" section as it is irrelevant; Science is expected to be objective. CHeers, BatteryIncluded (talk) 16:51, 16 January 2013 (UTC)[reply]
Hallo there BatteryIncluded (talk),
thanks for your general edits addressing the neutrality issue.
You surely have my personal consent for temporarly hiding the "==Student participation==" section:
Science is expected to be objective. (Indeed!)
And this "single blind" experiment IMHO seems a bit sexist too:
Why choosing a single undergraduate female student for just two weeks? Huh?
The opening anecdote of Wisdom of the crowds relates to Francis Galton's (1822-1911) surprise that the crowd at a county fair accurately guessed the weight of an ox when their individual guesses were averaged (the average was closer to the ox's true butchered weight than the estimates of most crowd members, and also closer than any of the separate estimates made by cattle experts). Well the crowd was made of 800 (sic!) people (800 tickets were issued)[2].
They didn't just sell a *single* ticket to an ... unwed... woman! LOL... I hope you caught my drift... ;O)
Catch you L8R?
  M aurice   Carbonaro  18:47, 27 January 2013 (UTC)[reply]
Hello. It has been established as standard procedure at NASA that morphology alone cannot be used as a biosignature of microscopic life detection. The section of "student participation" -in any aspect of the original study- brings no information to this subjec. CHeers, BatteryIncluded (talk) 21:03, 27 January 2013 (UTC)[reply]
Doesn't make you think that maybe "standardisation" is slowly killing "speculation"? If so... that is so sad indeed ... :O/... Cheers.   M aurice   Carbonaro 
Doesn't make you think that maybe "science" is slowly killing "pseudoscience"? If so... that is very good indeed. No Martians here, keep walking. Keep walking. Cheers, BatteryIncluded (talk) 14:01, 28 January 2013 (UTC)[reply]
Hypotheses non fingo LOL some mirroring makes forum interactions more *interesting* indeed. Ahem, BI... honestly I was thinking about Europans and NOT Martians. BTW maybe "NASA standardisation" is not synonim of "science"... Huh? Should we stop here our walk or should we engage in some tap dance together? If so please let's switch to our talk pages or, better, in private e-mails:
Wikipedia is not a forum unfortunately. Catch U L8R... :O)   M aurice   Carbonaro  17:32, 28 January 2013 (UTC)[reply]

References

  1. ^ Crenson, Matt (2006-08-06). "After 10 years, few believe life on Mars". Associated Press (on usatoday.com). Retrieved 2009-12-06. {{cite web}}: External link in |publisher= (help)
  2. ^ Introduction (page XII): Although Surowiecki's description of the "averaging" calculation (page XIII) implies that Galton first calculated the mean, inspection of the original 1907 paper indicates that Galton considered the median the best reflection of the crowd's estimate. (Galton, Francis (1907-03-07). "Vox Populi" (PDF). Nature. the middlemost estimate expresses the vox populi ). Galton's quotation from the end of this paper (given by Surowiecki on page XIII) actually refers to the surprising proximity of the median and the measurement, and not to the (much closer) agreement of mean and measurement (which is the context Surowiecki gives it in). The mean (only 1 pound, rather than 9, from the ox's weight) was only calculated in Galton's subsequent reply to a letter from a reader, though he still advocates use of the median over any of the "several kinds" of mean (Galton, Francis (1907-03-28). "Letters to the Editor: The Ballot-Box". Nature. 75 (1952). doi:10.1038/075509e0. my proposal that juries should openly adopt the median when estimating damages, and councils when estimating money grants, has independent merits of its own); he thinks the median, which is analogous to the 50% +1 vote, particularly democratic.

Carbon 14 used to date

Are you sure? 88.106.39.215 (talk) 10:25, 4 July 2015 (UTC)Allan M.88.106.39.215 (talk) 10:25, 4 July 2015 (UTC)[reply]

References

History Update

Whoever owns this page Talk:BatteryIncluded please may I offer this additional information:

In Jan 2012, the results of a study by the Primordia Institute of New Sciences and Medicine and by grants from Chang Gung University (FMRPD2T02) and Ming Chi University of Technology (0XB0)were published.[1] For those who were hoping that this analysis would confirm evidence for fossilized remains of living microorganisms, the results were disappointing. The researchers offer alternate, equally possible, explanations of what was observed, using nonliving chemical processes. They argue that minerals can display biomimetic properties and even can produce structures that resemble terrestrial bacteria as well as more complex forms that resemble platelets and films by amorphous-to-crystalline transformations and by binding to substrates.

They remind the reader that so-called nanobacteria described in geological samples as well as the putative nanobacteria observed in human body fluids and tissues have been shown to represent nonliving biomimetic mineral nanoparticles; and that Morphology is a poor indicator of biogenicity, and it should not be used as the sole evidence for life. BSmith821 (talk) 20:53, 29 July 2013 (UTC)[reply]

References

  1. ^ Martel, Jan (2012). [earth.annualreviews.org "Biomimetic Properties of Minerals and the Search for Life in the Martian Meteorite ALH84001"]. Annu. Rev. Earth Planet. Sci. 40: 167–193. doi:10.1146/annurev-earth-042711-105401. {{cite journal}}: Check |url= value (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)

Theories on what the unknown "worm" object could be?

I'm sorry if I missed it in the article be assumingly given all of the opposition to it being a lifeform there must be some suggestion to what it could instead be in that picture? Shouldn't this be expanded upon more or should we assume or is it just assumed it's a strangely shaped rock? Robo37 (talk) 19:16, 26 November 2013 (UTC)[reply]

The scientists' consensus is that it is not a fossil, and that microscopic shapes alone cannot be used as a reliable indication of life. Had it been a microfossil, the premise is that it resembles a chain of bacterial cocci (spheres), not a worm. Cheers, BatteryIncluded (talk) 00:42, 27 November 2013 (UTC)[reply]
I think it is more accurate to say that the consensus of many - but not all scientists - is that it could be formed by inorganic processes. They haven't proved that it is not a fossil, and the hypothesis of life remains compatible with all the observations. But the bar is very high for proving existence of past or present day life on Mars, as indeed it should be, and most scientists would say the case has not been proven that this was life as it could be due to inorganic processes. We might well find more meteorites from Mars of the same age as this meteorite that clarify the situation, or evidence from our rovers from Mars may make it all clearer and prove either way that it is inorganic or that these are fossil microscopic lifeforms. That's common on Earth also, in particular evidence of early microscopic life on Earth is often controversial, with various fossils held to be microbes or stromatolites by some researchers and not by others, and then sometimes the situation is resolved by more data, e.g. presence of organics clearly dated to the time of origin of the structures. Microsocopic fossils of alleged early microbes on Earth are often particularly controversial. Robert Walker (talk) 11:35, 15 September 2016 (UTC)[reply]

List of Hypothetical Biogenic features in ALH84001

I've just added this as a new section. I was astonished to see that the article didn't even mention magnetite, the strongest evidence originally presented for life in the meteorite. Nor did it mention the carbonate modules or the workshop on the limitations of size for living cells which was held in 1999 soon after the discovery.

Anyway I took some material recently deleted from the Life on Mars article as a basis, and re-read the original 1999 paper and some other material and then wrote up this list of some of the main hypothetical biogenic features. Robert Walker (talk) 11:29, 15 September 2016 (UTC)[reply]

Removal of conclusions of limitations of size workshop

@BatteryIncluded: What's your reason for removing the material about the conclusions of the 1999 limitations of size workshop and the cite of this workshop? I know we've had our differences with me attempting to get you to include information about modern ideas for possibilities of present day surface and near surface life on Mars in the Life on Mars article and you labeling me a troll for the attempt. I have given up on that, but I thought you would find this uncontroversial as it is about past rather than present day life, and it definitely fits the noteworthy criteria for wikipedia. It's a publication of the Space Studies Board of the National Research Council in the US - you can't get much more establishment / noteworthy than that.

They found that though present day life can't be smaller in volume than the figures you retain in the article, that earlier forms of life could be as small as 50 nm in diameter, and they also cover other hypotheses for ALH84001 such as that they could be fragments of larger organisms. Do please check the cite as I have only just added this and perhaps you haven't had time to read it yet.

This is the material you removed. If you check out the cite, you'll see that I have summarized exactly what they say in the summary at the head of the book. Which was published in 1999 and mentions ALH84001 in the intro as one of the main motivations for the workshop.

However, a workshop on the limitations of size of microbes in 1999 found that though modern nanobacteria can't be smaller in volume than the interior of a sphere of diameter 250 ± 50 nm, primitive microorganisms based on a single-polymer system, for instance, RNA based, with ribozymes (catalytic RNA) taking the place of ribosomes as enzymes for cell replication, could be as small as a sphere 50 nm in diameter. Cells could also shrink after death, or the fossils could be remains of fragments of larger organisms, or they could be pathogens or symbiotes which depend on a host, or they could live in consortia of smaller cells unable to survive independently on their own, or they could be based on biological systems different from the ones we understand. [1]

Robert Walker (talk) 13:52, 15 September 2016 (UTC)[reply]

List of features ≠ list of hypotheses. Besides, I do not feed trolls, remember? BatteryIncluded (talk) 13:57, 15 September 2016 (UTC)[reply]
Well why include mention of the limitation of 250 nm for modern life, and remove the limitation of 50 nm for precursors for modern life? And why remove the cite? This is the section from the book which I summarized [1]

"Whereas Panels 1 and 2 indicated that a cell operating by known molecular rules—with DNA or maybe RNA, ribosomes, protein catalysts, and other conventional cell machinery—would have a lower size limit of 200 to 300 nm in diameter, Panel 4 suggested that primitive microorganisms based on a single-polymer system could be as small as a sphere 50 nm in diameter. There is no assurance that primordial cells would have been this small or, if they were, that such minute cells would have been more than transitory features of early evolution. Nonetheless, unless one is willing to posit that everywhere it has arisen, life has evolved a biochemical machinery comparable to that seen on Earth, the rules that govern minimum cell size may not be universal. In fact, as explored by Panel 3, there are a number of ways that living cells or fossils might fall below the minimum size deemed likely by cell biologists and ecologists. On Mars or Europa, fossils might preserve a record of biological systems different from those we understand—perhaps early products of evolution that made do with a small complement of functional molecules. Organisms of modern biochemistry might become small by being pathogens or living in consortia—that is, by using the products of another organism's genes. Or, fossils might preserve remains that shrank after death, or parts of organisms rather than complete cells—both are common in the terrestrial record." (emphasis on 50 nm added by me to highlight it in context on the page)

- along with later material on RNA life based on ribozymes in the section by Panel 4 later in the book. I am not a troll.
Everything I said on the talk page for Life on Mars Talk:Life_on_Mars is sincere and heavily cited to modern journals including the 2013 conference on the Present Day Habitability of Mars[4], the work of DLR in Germany, of Nilton Renno highly respected leader of the Curiosity "Weather station on Mars" team and one of the top experts on surface conditions on Mars, and other top ranked researchers in the field. There was no justification for hiding the suggestion to include this material from the talk page. But as I said I've given up on the attempt to get that material included in wikipedia, but that doesn't make me a troll, it just makes me someone who has tried to get something notable included in wikipedia and failed - a common occurrence nowadays, sadly. Robert Walker (talk) 15:27, 15 September 2016 (UTC)[reply]
Your Martian invasion prophesy could be a notable story for the cheap tabloids, not Wikipedia, Troll. BatteryIncluded (talk) 15:46, 15 September 2016 (UTC)[reply]
Once again, why include mention of the limitation of 250 nm for modern life, and remove the limitation of 50 nm for precursors for modern life? And why remove the cite? Calling me a troll for attempting to get material restored on Planetary protection to Human mission to Mars after it was deleted is no answer, it's just changing the subject! Robert Walker (talk) 18:31, 15 September 2016 (UTC)[reply]
  1. ^ a b Size Limits of Very Small Microorganisms: Proceedings of a Workshop (1999). 1999.

Thought it was dead?

I saw a mention of this in a new-ish Cosmochemistry textbook by McSween, where he says that scientific consensus has always been that these are not of biological origin, but that the controversy itself is significant to the history of the science. That's the POV I've been aiming at. I'll see if I can find that source and add it. The last really secondary source in the article is a news piece from 2006. Geogene (talk) 20:29, 15 September 2016 (UTC)[reply]

You probably mean this? [5]

"In any case the putative fossils appear to be far too small to represent living forms and could at best be appendages or fragments of organisms. The controversy over life in this Martian meteorite has now largely subsided with the consensus that abiotic processes provide more compelling explanations for all the observed evidence. However, the interest in ALH84001 has generated new research into the authenticity of various chemical and physical biomarkers and spawned a reinvigorated Mars exploration program focused on the search for life."

However, on the particular detail of whether the fossils are too small to be living cells - that may be true of a two-biopolymer system such as we have for all modern life, based on both RNA and DNA then the smallest structures in ALH84001 are probably too small, though there is evidence that some modern cells are of sizes approaching this (see page 19 of this report [6]).
Also it is a respectable hypothesis that the two biopolymer system was preceded by a single biopolymer system as that after all is the RNA World hypothesis. [7]. A 50 nm cell would be too small to contain much by way of ribosomes at 20 nm diameter even for prokaryotes, but it could contain the much smaller ribozymes of the RNA world hypothesis.
Most of the discussion of the smallest cell size on Mars seems to focus on the smallest size for "life as we know it" in a two biopolymer RNA + DNA cell - but in the case of ALH84001 especially, you are talking about a sample from Mars only 400 million years after formation - it might well have modern life precursors. Older than the oldest lifeforms known from Earth. The discussions in the 1999 workshop mention this possibility frequently as well as the possibility of life based on different biochemistries from Earth life that might permit small sized cells. For some reason it seems to have been forgotten or rarely mentioned in more recent discussions, they tend to just look at the limitations of size of modern life. I don't know why that is. But they haven't disproved the RNA World hypothesis AFAIK. Just don't tend to mention it in the context of ALH84001 any more.
I don't know what that means for wikipedia. Was @BatteryIncluded: right to just remove mention of 50 nm RNA based cells as a possible explanation for the structures because it was based on the 1999 reference and is seldom mentioned nowadays? What do you think? Robert Walker (talk) 22:45, 15 September 2016 (UTC)[reply]
Yes, that source. I'm more interested in the gestalt that scientific consensus favors abiotic processes. Minimalist RNA-based lifeforms would seem to be a drastic retreat from the original McKay theory that has Martian bacteria precipiating magnetite and causing the precipitation of carbonates as well. That seems like the kind of biochemical toolkit you would need lots of genes and a significant proteome for. One of the sources you gave seems to have alluded to that [8] when it says that any ancient RNA world would probably not leave identifiable traces in the rock record. I'm also taking it as an unstated assumption that any RNA world leftovers on Earth or Mars would have quickly either devoured by prokaryotes, or that they took on new careers as viruses. I would need to see a diff of specific content before giving a definitive opinion, but generally speaking if nobody's still talking about it then probably not. Geogene (talk) 00:25, 16 September 2016 (UTC)[reply]
Oh, I see. So in your view it probably would depend on finding some present day research suggesting this. Or could it be included as a historical note that back in 1999 researchers explored the possibility of 50 nm cells based on the RNA World hypothesis?
I agree that RNA based life is unlikely to survive on Earth except possibly in viruses, though there is the hypothesis of the nanobacteria which probably would be RNA based if they exist, however the current consensus seems to be that they are inorganic or at least, non biological, don't think there is much research going on in support of nanobacteria any more.
With Mars, however, until we have evidence of what is actually there, there's the possibility that it is still an RNA World to this day or has some alternative biology we have never encountered on Earth. And ALH84001 would only have fossils of early life. That's a good point, as far as I know in the 1999 workshop, they don't go into how such small microbes would create magnetite. A search of the book for "magnetite" turns up 0 matches.
But they do have an estimate of the number of genes of RNA based on ribozymes that could fit into a cell of the size of the smallest putative microbial features in ALH84001. It depends very much on how efficiently the genes are packed. If they are packed as efficiently as the most efficiently packed viruses, then they calculated that the smallest features of ALH84001 could have 5 genes each of 1500 base pairs for ligase, replicase, monomer synthase, fatty acid synthase, and membrane synthase ribozymes, and then it was a question of whether that was enough for a primitive lifeform. Calculation here [9]. However ALH84001 contains cell like structures of a wide variety of sizes, including ones the size of ultra microbacteria of 200 - 300 nm in diameter and all the way up to ones of 1 - 2 microns in size. So the magnetite doesn't have to be produced by the nanobacteria, if that's what they are. Or am I missing something. Robert Walker (talk) 01:13, 16 September 2016 (UTC)[reply]
@Geogene: I've just found a much more recent cite to the hypothesis that the structures in ALH84001 represent organisms from an RNA world. This is from a book published in 2012 by the Cambridge University Press, in the chapter "Towards a Theory of Life" by Steven E. Brenner (microbiologist at the University of California) and Paul Davies. [1]

"Why should proteins be universally necessary components of life? Could it be that Martian life has no proteins? Here, our earlier observations about the possibility of ancestral RNA-based life on Earth are relevant. Life forms in the putative RNA world (by definition) survived without encoded proteins and the ribosomes needed to assemble them. Thus, our additional "half example" of life on Earth refutes the "protein theory of life" and undermines the argument that the structures observed in the Alan Hills meteorite are too small to be remnants of living cells. If those structures represent a trace of an ancient RNA world on Mars, they would not need to be large enough to accomodate ribosomes (Benner 1999). The shapes in meteorite ALH84001 just might be fossil organisms from a Martian "RNA world".

So I think you can say that this hypothesis of small cells from an RNA World for ALH84001 is still being talked about. It's not been refuted, nor is it fringe science, just a minority hypothesis that is still being entertained by some scientists, we have two notable cites, it's modern, and fits the wikipedia criteria for notability - unless I'm missing something it seems to tick all the boxes for a mention in wikipedia, shouldn't it be included in the article? Robert Walker (talk) 03:29, 16 September 2016 (UTC)[reply]
No. Fringe is fringe is fringe is fringe. A Martian invasion is NOT happening. Live with it. BatteryIncluded (talk) 13:30, 16 September 2016 (UTC)[reply]
What does that comment have to do with anything? Robert Walker (talk) 13:59, 16 September 2016 (UTC)[reply]
Typical troll reply. Here it goes for the nth time: WP:Fringe theories. BatteryIncluded (talk) 14:04, 16 September 2016 (UTC)[reply]
I am talking here about the hypothesis that the small cells in ALH84001 are RNA world cells. RNA World is not a fringe theory and RNA World cells can be much smaller than DNA cells because they have only one informational polymer instead of two which hugely reduces the complexity of the cell. They also don't have proteins and instead use the much less bulky rybozimes which are made up of fragments of RNA joined together. This makes it possible for an RNA World cell to be a fraction of the size of a DNA cell. Whatever early life was, it can't possibly have been DNA life as the system is far too complex to have arisen in one jump from non biological precursors. One possibility is that the simpler early precursors were also smaller than present day cells as well as simpler. None of that is fringe science and the limitations of size book was a publication of the National Research Foundation and the 2012 book was edited by distinguished editors Chris Impey, Jonathan Lunine, José Funes and published by the Cambridge University Press. Nothing in any of this raises fringe science warning flags as far as I can see. Please explain yourself. Robert Walker (talk) 21:27, 16 September 2016 (UTC)[reply]

1) Bull shit. they are not cells. 2) My friend Bubba has a "hypothesis" that competes with yours: There are invisible pink unicorns all over Mars. Can we add it too, Troll? Peer-review is a b!tch, ain't it? BatteryIncluded (talk) 21:42, 16 September 2016 (UTC)[reply]

I think you are the one trolling me. Sorry to have to say so. But I'm not going to rise to it, and obviously this conversation is at an end unless someone else has any views on the matter. And as with our discussions on the talk page of Life on Mars where I attempted to get the most recent research on habitability of the warm seasonal flows and other surface and near surface proposed habitats on Mars such as Nilton Renno's ice / salt interface droplets included, obviously this means this article is not going to mention the RNA World hypothesis for the structures on ALH84001. Though I have no idea why not. Robert Walker (talk) 00:22, 17 September 2016 (UTC)[reply]

I'm not sure I have a strong opinion on this either way. I just want the readership to take away that it's probably not something to get excited about, although minority opinions should get their views in as well. I agree with what seems to be BatteryIncluded's opinion that this life on Mars is starting to look like a non-falsifiable construct, but Cambridge University Press is usually reliable. Geogene (talk) 02:50, 17 September 2016 (UTC)[reply]

Oh, I think it is like microbial fossils on Earth. There's a lot of controversy about those too. See section 3.3 recognizing microfossils in this paper [10]. I don't think it's going to be resolved by studying ALH84001 on its own, only by studying other Martian meteorites whenever we find them or studying in situ on Mars. The idea that Mars had life in the early solar system is certainly very respectable and many think it may still have life today and as I've tried to get mentioned in the Life on Mars article there are many teams of researchers currently researching into habitability of the warm seasonal flows and salt / ice interfaces and running tests with Earth microbes to see how they survive in similar environments etc. They certainly haven't given up on present day life on Mars and some of them are extremely optimistic about finding it while others are pessimistic.
There's a complete spectrum of views on this topic all the way from the view that it is unlikely, to, of course, Levin's view at the other extreme that it has already been detected by Viking - now also accepted as a possibility by a few other researchers based on the recent discovery through re-analysing the raw Viking data of rather puzzling apparent circadian rhythms in the data not in sync with the temperature changes - and a whole range of views in between. I summarized it in my article here which I wrote as a draft for wikipedia summarizing the latest research much of it published only in the last two or three years - but it was never accepted for publication here so I published it on my science blog instead and as a kindle booklet: | Present day habitability of Mars#Views on the possibility of present day life on or near the surface]. The article is still there in case anyone decides that it is okay for wikipedia after all. I've done everything I can to make it as good as I possibly can and can't improve it any more.
Anyway on this article I certainly don't want the reader to take away the message that it is likely either. Just that it is a hypothesis that some scientists have entertained and continue to entertain. Many would say that life on Early Mars is quite likely, much fewer though would say that we have got evidence of it already in ALH84001. If we do find early life though especially if it contains fossilized remains of precursors to DNA based life, it may well consist of tiny cells or in other ways be unlike present day life and hard to recognize. I think that's also a reasonably fair bet. Which of course doesn't prove that ALH84001 is that evidence :). Robert Walker (talk) 03:29, 17 September 2016 (UTC)[reply]
@Geogene:, for years, Robert has trolled the Mars-related articles at WP pushing his belief on current life on the surface of Mars and on an imminent fatal Martian invasion. For years, I have cleaned up after him. As I will for the years to come. When he reads that any inert physical environment may be potentially "habitable", he hears "inhabited", AND the Martians are going to kill us all as soon as any Mars sample-return mission happens. He will do WP:synthesis worth a Nebula Award, and torture the references so that they will confess to anything. That is just in the Talk pages. He is all yours to entertain if you enjoy such dynamics. I was done with his paranoid project years ago, now I just delete the BS without feeding the troll. Cheers, BatteryIncluded (talk) 04:02, 17 September 2016 (UTC)[reply]
@BatteryIncluded: and @Geogene: This is not true, you have been mislead by a troll who deleted my work some years back. I have only asked for you to include the latest scientific research which shows that present day life on the surface of Mars is a possibility - microbial life and lichens. I had contributed to the articles for some time on this topic with no problems at all, when one day when I was writing an article on the back contamination risks of samples returned from Mars, a troll came and wrote outrageous statements about me, saying that I was mentally deranged and promoting doomsday scenarios. There was no truth at all in what he said. He somehow managed to persuade several other people that he was telling the truth and they then went on a campaign together and removed all the content I had ever contributed to wikipedia on planetary protection issues, and in the process also, material on the present day habitability of Mars contributed by many authors was removed too (I added just a couple of sentences on that topic but that was enough for them to remove the entire topic from wikipedia). They finally rewrote the entire Planetary Protection article, until it was a nonsense of confused and mistaken material, much of it incoherent and some of it nothing to do with the topic.
I tried to stop them with RfCs and such like but they just voted against me and said we have reached a "rough consensus", and deleted the articles anyway after letting the RfCs run for only a day or so without attempting to get an impartial third party to close the RfC. And reverted any attempts I made to stop them. Anyway finally @Robert McClenon: stepped in when they did that rewrite of Planetary protection saying they had to stop and leave that article to me, at which point they did stop and I was permitted to get that article back into shape again. You can see the quality of my work in this topic area from the current version of that article which is 50% my own work. I think it is obvious to anyone reading it that it is not the writings of a deranged troll :).
At some point in the proceedings I tried to get the deletions reverted but the troll convinced the wikipedia administrators that I was a deranged troll and so I wasn't able to achieve that. Indeed, they were debating taking action against me. But none of the things he said about me were true. Finally in the middle of that debate he suddenly announced that he was leaving wikipedia and the action was closed with no conclusion. That's how it unfolded from my perspective.
The article just covered the material on sample return hazard assessments by the NRC and the ESF and their recommendations to build a sample return containment facility as well as criticism by others including Carl Sagan, who consider that such a facility is not sufficiently safe, okay if the design worked perfectly but could release Mars organisms in case of accidents and lapses of procedure, and from the Nobel prize winning microbiologist Joshua Lederberg who was very active in promoting need for caution for sample returns from outside of Earth, and it also covered Zubrin's views that planetary protection is unnecessary and a full spectrum of views on the topic.
I never said any of the things he attributed to me, and far from promoting doomsday scenarios I am very active in debunking them on my science20 blog. But only Robert Zubrin and a very few others say that it is safe to return samples from Mars to Earth without taking any precautions at all. That is a minority position. The problem is that a sample from Mars could in the most interesting scenario include life based on a completely different biology. The dangers from a return from Mars are similar to those from releasing artificial lifeforms created in a laboratory, for instance not based on DNA but PNA instead (something we may be able to experiment with in the laboratory in the near future). Though the risk may be low, hard to assess, most scientists think we should not take this risk and precautions are necessary in view of the possibility of harm to the ecosystems of Earth, not just to humans. For instance if the XNA based life took over from green algae in the sea, perhaps because it is more efficient at photosynthesis, that obviously would have a major impact on marine ecosystems, just by way of example.
I understand that those who want to send humans to the Mars surface don't like to hear this. But many scientists do say that there is a realistic possibility of life in the surface habitats. You have said many times that cosmic radiation sterilizes the upper layers of the Mars surface. That is true, but only over timescales of hundreds of millions of years for dormant life. If the radiation levels were so high that a radioresistant microbe couldn't survive long enough to replicate and couldn't heal itself, it would be as hazardous as nuclear waste (since radiodurans lives in reactor cooling ponds) and humans would not survive for long at all. In actuality the levels of cosmic radiation are similar to the interior of the ISS and of course are easily survived by microbes on timescales of years, centuries, and indeed even millennia. Until recently scientists thought that there could be no liquid water exposed to the Mars surface for what seemed very good reasons - water and even ice would rapidly sublime into the near vacuum of the atmosphere. But recent discoveries starting with Phoenix in 2008 showed that liquid water can form on the surface of Mars through deliquescing salts, very salty but experiments in Mars simulation conditions show that it could, depending on the mix of salts, be habitable for salt tolerant extremophiles. Other research since then also showed that water can form in tiny droplets on salt / ice interfaces, also that the RSL features on Mars actually contain hydrated salts and are thought to have flowing thin films of salty water seasonally. Curiosity has also detected liquid water indirectly beneath the sand dunes it travels over (most think that particular habitat is too cold for life, Nilton Renno however thinks there is a possibility of microfilms making it locally habitable).
And indeed there is evidence of a possible RSL on Mount Sharp as a result of which they may have to do a large detour to prevent it from contaminating them. See NASA Weighs Use of Rover to Image Potential Mars Water Sites. ESA's ExoMars has search for past life as its primary objective but has the search for present day life as a secondary objective. So it's possible even in equatorial regions and this is no longer a minority view held by a few scientists like Gilbert Levin but a mainstream view of many of the researchers in this topic area. Also the DLR group in Germany in another development have found that some lichens and cyanobacteria are able to survive simulated Mars conditions in partial shade and even metabolise and photosynthesize without any water at all using only the 100% night time humidity on Mars - which causes the early morning frosts first seen in the Viking photos.
All this is mainstream science and I can provide links for all of that to highly rated scientific journals and papers and video presentations from conferences. See the citations for my article Draft:Present day habitability of Mars which has numerous references, every statement in that article of any significance is cited, so you can follow them up to find out more about this research and the views of the researchers on the possibility of present day life on Mars. Hope this helps! My only wish is to improve wikipedia and make sure it is comprehensive and accurate in this topic area and I have no wish to promote any particular view on the topic here over any other view.
I do of course have views of my own, indeed very strong views which I have expressed on my science blog and talked about on David Livingston's "the Space Show" and presented in a talk to a conference on the search for life in the subsurface oceans of Europa and Enceladus in Oxford last summer. But I would never suggest putting those views into an encyclopedia. Indeed I removed a cite of my blog from one of the planetary protection articles which someone else added, as not WP:RS according to the criteria of wikipedia in my view, because it presented my own personal views on the topic in a personal blog, and was not a peer reviewed paper. Robert Walker (talk) 13:53, 18 September 2016 (UTC)[reply]
There you go folks, again straight from the trolls mouth: Living Martians on the surface, death on Earth by Martians, SPAMING his paranoid web site, Wikipedia ganged up on him (for no reason at all), and a world-wide scientific cover up. And don't even get him started on the "benevolent radiation environment" on the surface of Mars. Feed him another cookie. I won't. BatteryIncluded (talk) 15:15, 18 September 2016 (UTC)[reply]
I just linked to my blog to show that I regularly debunk doomsday scenarios. My most recent article is a petition to ask Youtube to stop running ads on doomsday videos because they cause vulnerable people to become suicidal and scared (an issue first brought to our attention by NASA scientist and former head of the Sagan Institute, David Morrison (astrophysicist). I spend hours a week answering comments and messages from scared vulnerable people to reassure them that various doomsday hoax stories and videos are nonsense - to say I promote doomsday scenarios could hardly be further from the mark! I've removed the link now, since you objected, but I had no intention at all of promoting my blog here!!!!
The aim of the National Research Council, the European Space Foundation, Carl Sagan, Joshua Lederberg and all those who have written on this topic is to protect Earth. For the same reason, we take precautions to make sure that harmful diseases are not released from biosafety laboratories, and take many precautions to make sure that experimental bioengineered and synthetic lifeforms created in laboratories can't replicate "in the wild". This is also written into the Outer Space Treaty and there are meetings of COSPAR, international scientists, every two years, to discuss the detailed provisions. We also have planetary protection officers - NASA's Planetary Protection Officer is Catharine Conley. You couldn't be more mainstream than this.
The current material in wikipedia in Life on Mars has a "proof" of the impossibility of life in surface liquid layers is based on an amalgation of citations that predate Phoenix and refer to dormant rather than active life. The mainstream view is that it is possible, to the extent that they probably won't let Curiosity approach closer to the RSL on Mount Sharp than a few kilometers to avoid contaminating it with Earth life. There are dozens of papers on the topic published each year but this entire topic area can't be included in Life on Mars because of this purported "proof" even though they have passed peer review. Wikipedia should not undertake its own independent process of peer review like this! If it's published in a WP:RS source and passes notability, there shouldn't be an additional step of peer review by a wikipedia editor. Note that this is not a community decision to exclude this material, it is an individual editorial decision by @BatteryIncluded:.
My only reason for saying these things is to try to get this material included. I am not the least bit interested in participating in yet another debate here if there is no chance of this happening. I expect that if ExoMars or some other mission finds life on Mars in surface habitats, Wikipedia will finally get edited to say that Mars surface life is possible and include the results of all this research??
And apparently also for similar reasons, though I don't see the connection myself, it won't mention the hypothesis that the smallest structures in ALH84001 could be RNA World cells from early life precursors either, although I gave excellent cites - the most reliable of WP:RS you could have in this topic area. Anyway I'd better stop, I see I've been drawn into yet another of these strange discussions with @BatteryIncluded: They never get anywhere so what's the point in continuing? Robert Walker (talk) 20:19, 18 September 2016 (UTC)[reply]
Please do not feed the trolls. Thank you. BatteryIncluded (talk) 18:26, 18 September 2016 (UTC)[reply]
To anyone reading this the "Do not feed the Trolls" sticker is just an individual decision by @BatteryIncluded:. Anyone can add such a sticker to any conversation. Do feel free to continue this conversation if you don't think I'm a troll.Robert Walker (talk) 22:05, 18 September 2016 (UTC)[reply]

I'd like to point out - in this entire conversation thread, the only argument that @BatteryIncluded: has given for not mentioning RNA world cells hypothesis here is an ad hominem one. He claims that I am a troll because I wanted to restore a section on on planetary protection that was deleted from Human mission to Mars and because I want to restore a section on present day habitability of Mars to the Life on Mars article and want to include the material in Draft:Present day habitability of Mars in wikipedia. I've argued strongly that this does not make me a troll, not remotely so. Just someone who thinks that wikipedia is missing some material that I consider to be notable and to pass WP:RS and has tried to get included on that basis. But whatever your views on that, it has nothing at all to do with the topic of the RNA World hypothesis for the ALH84001 cells. And anyway - surely Wikipedia shouldn't have a blanket policy to exclude a particular topic such as present day habitability of Mars from the encyclopedia? It's certainly not a community decision to do so.

Whether or not you think the person advocating that the topic is included is a troll or not, it should be a question based on the notability of the topic. And if papers have been published and passed peer review in WP:RS that's the only criterion. Even if you have a "proof" that it is impossible - wikipedia doesn't do peer review, the WP:RS do that and it is up to the reviewers of the journals to provide those arguments, not us.

So the question is, does the material on RNA World cells pass this requirement of WP:RS. That's the only thing to consider when deciding whether to include it. So anyway I'll summarise the evidence in a new section. Robert Walker (talk) 10:52, 19 September 2016 (UTC)[reply]

Also just to say @BatteryIncluded: was responsible for removing the section Possibility of enough liquid water to support life from the Water on Mars article. I don't know the reason but he has some kind of agenda on removing some of the material that supports possibilities of past or present day life on Mars. He says it is "peer review" (see above where he says "Peer-review is a b!tch, ain't it?") but according to its own guidelines, Wikipedia shouldn't do peer review. It should publish anything that is notable and published in WP:RS and it is those publications that do the peer review. Even fringe science should be published if notable and marked clearly as fringe. But this is not fringe science, it is just minority view science and in some cases majority view science nowadays due to changes of scientific opinion over the last eight years. Robert Walker (talk) 22:26, 21 September 2016 (UTC)[reply]

RNA World Cells Hypothesis - summary of the cites - do they pass WP:RS?

The cites are

1. A chapter in the book "Frontiers of Astrobiology" published in 2012 by the Cambridge University Press, in the chapter "Towards a Theory of Life" by Steven A. Benner (notable as the first person to synthesize a gene amongst many other accomplishments) and Paul Davies. [2]

"The reader can decide the extent to which the structures discovered in the Alan Hills meteorite resemble Earthly microbes. But in the decade following the initial publication of the meteorite's discovery, some in the biological community began to argue that the intriguing microbe-like structures could not be remnants of cells because of their small size, only 100 nanometers across. This was "too small" to be life. But too small for what form of life? The most frequently cited arguments against McKay's cell-like structures as the remnants of life compared their size to the size of the ribosome, the molecular machine used by terran life to make proteins. The ribosome is approximately 25 nanometers across. This means that the "cells" in Alan Hills 84001 can ohold only about four ribosomes - too few, supposed by many biologists, for a viable organism. The syllogism is clear. Proteins are necessary for life Ribosomes are necessary to make proteins. Martian cells are too small to hold ribosomes. Hence, Martian cells are too small to be life....

"Why should proteins be universally necessary components of life? Could it be that Martian life has no proteins? Here, our earlier observations about the possibility of ancestral RNA-based life on Earth are relevant. Life forms in the putative RNA world (by definition) survived without encoded proteins and the ribosomes needed to assemble them. Thus, our additional "half example" of life on Earth refutes the "protein theory of life" and undermines the argument that the structures observed in the Alan Hills meteorite are too small to be remnants of living cells. If those structures represent a trace of an ancient RNA world on Mars, they would not need to be large enough to accomodate ribosomes (Benner 1999). The shapes in meteorite ALH84001 just might be fossil organisms from a Martian "RNA world".

2. The 1999 workshop on Limitations of Size published by the =Soace Studies board and published by the National Academy Press. [3]

"Whereas Panels 1 and 2 indicated that a cell operating by known molecular rules—with DNA or maybe RNA, ribosomes, protein catalysts, and other conventional cell machinery—would have a lower size limit of 200 to 300 nm in diameter, Panel 4 suggested that primitive microorganisms based on a single-polymer system could be as small as a sphere 50 nm in diameter. There is no assurance that primordial cells would have been this small or, if they were, that such minute cells would have been more than transitory features of early evolution. Nonetheless, unless one is willing to posit that everywhere it has arisen, life has evolved a biochemical machinery comparable to that seen on Earth, the rules that govern minimum cell size may not be universal. In fact, as explored by Panel 3, there are a number of ways that living cells or fossils might fall below the minimum size deemed likely by cell biologists and ecologists. On Mars or Europa, fossils might preserve a record of biological systems different from those we understand—perhaps early products of evolution that made do with a small complement of functional molecules. Organisms of modern biochemistry might become small by being pathogens or living in consortia—that is, by using the products of another organism's genes. Or, fossils might preserve remains that shrank after death, or parts of organisms rather than complete cells—both are common in the terrestrial record." (emphasis on 50 nm added by me to highlight it in context on the page)

Are these WP:RS? @BatteryIncluded: argued that the 1999 workshop cite is too old to be mentioned in the article - though he didn't come up with any later refutation of its conclusions by anyone else. The 2012 cite shows that these ideas are still current in my view. The 2012 cite validates the 1999 cite as still valid in my view so long as both cites are accepted as WP:RS. Note that Benner, the principal author of the 2012 cite, is one of the contributors to the 1999 workshop with 34 mentions in the section on the conclusions of Panel 4.

The only question under consideration here should be whether these cites are notable and WP:RS. If they are, surely the RNA World cells hypothesis should be mentioned in the article. Please leave my hypothesized motives for suggesting this addition out of this discussion! Please just discuss whether it is WP:RS and whether it should be included. Thanks! Robert Walker (talk) 10:52, 19 September 2016 (UTC)[reply]

I plan to reinstate this material in the next day or two. @BatteryIncluded: came up with no good reasons to remove it, and he is no longer contributing to wikipedia. I am not sure why - his talk page mentions a block for abusive language and another block for alleged sock puppetry - but I'm not sure if he is still blocked, or has voluntarily stopped editing here. Robert Walker (talk) 12:30, 4 February 2017 (UTC)[reply]
Have just added it in as a new section, see Allan Hills 84001#RNA World Hypothesis and other proposals that could be consistent with such small structures as cells Robert Walker (talk) 21:04, 11 February 2017 (UTC)[reply]
I don't see this language in the current article. Was it deleted again?
I just read the interesting discussion of ALH84001 in Jo Marchant's The Human Cosmos (2020). She wrote that the NASA team still thought their evidence supported a Martian biologic origin for the structures found in the meteorite as of 2019. Pete Tillman (talk) 00:41, 10 November 2024 (UTC)[reply]

References

  1. ^ Cite error: The named reference Brenner was invoked but never defined (see the help page).
  2. ^ Steven a. Benner, Paul Davies, editors: Chris Impey, Jonathan Lunine, José Funes (15 Nov 2012). Towards a Theory of Life, in Frontiers of Astrobiology (Page 37). Cambridge University Press. {{cite book}}: |last1= has generic name (help)CS1 maint: multiple names: authors list (link)
  3. ^ Size Limits of Very Small Microorganisms: Proceedings of a Workshop (1999). Soace Studies board, National Research Council,NATIONAL ACADEMY PRESS. 1999.

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