Microbial mats traced in Mars sediment? Noffke's hypothesis

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This work looks solid and careful to me:
http://online.liebertpub.com/doi/pdf/10.1089/ast.2014.1218

On Earth, in semiarid regions, mats of bluegreen algae develop in lakes and ponds which subsequently may completely dry up---the microbial material becoming part of a sedimentary sandstone formation with visibly distinctive features.

Nora Noffke (BS 1990 MS 1992 Tübingen PhD1997 Oldenburg) is a geomicrobiologist who has made a specialty of studying "microbially induced sedimentary structures" (MISS) e.g. in arid parts of Australia and south Africa, including very old structures e.g. age > 3.7 billion years. She has identified remarkable similarities in photos of Mars surface taken by the mast camera of the Curiosity rover.

Distinctive features where it looks like the mat has blistered and formed an empty pocket, or where it has torn and folded over as if washed by a current, or where a small portion the drying mat has actually rolled up.

She has identified flat folds, and roll-ups, and distinctive tears and cracks in the Mars rover photos of a dry lake bed, and prepared comparisons with photos taken of Earth MISS.

So there is this hypothesis, which can be tested by further/closer examination
 
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marcus
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I imagine most people prefer "little green men" or ancient ruins of an advanced civilization or even a love letter by John Carter but this really could be IT - the beginning of recognizing that Life is something the Universe "just does", a natural consequence of physical laws. I find this extremely exciting and possibly the best reason I've heard in decades to risk a manned exploration. OTOH if it results in advances in current robotic abilities, I'm good with that, too :)
 
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Signs of life on Mars (if not directly connected to life on Earth!) would certainly suggest that life is very common in the universe.
It would also make the Fermi paradox more pressing - at least one step towards interstellar colonization has to be extremely unlikely, and we don't know where this step is yet and if we passed it.
 
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Garth
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Thank you again marcus for some very interesting links.

Agreed, potentially the most exciting discovery for exobiology.

It would also make the Fermi paradox more pressing - at least one step towards interstellar colonization has to be extremely unlikely, and we don't know where this step is yet and if we passed it.
As for the Fermi paradox - either they are not there, anywhere, or it is the 'zoo hypothesis' - we are in quarantine until we prove ourselves fit to join the galactic community, which I don't see happening any time soon. :(

Garth
 
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Garth
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Signs of life on Mars (if not directly connected to life on Earth!) would certainly suggest that life is very common in the universe.
Of course We may all be Martians!

Garth
 
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That article sounds odd. There is no evidence that molybdenum or boron is necessary for the formation of life, and water is absolutely vital for earth-like life.
 
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Garth
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That article sounds odd. There is no evidence that molybdenum or boron is necessary for the formation of life, and water is absolutely vital for earth-like life.
Apparently they are required as templates for the formation of RNA, a precursor for life: Elements and the Origin of Life. Boron and Molybdenum.

Water has an ambivalent effect on the formation of life, on the one hand biochemicals are water solvent, on the other they tend to dissolve in its presence and thus prevent polymerisation. On Earth the Moon's tidal effect is sometimes thought to be important as a way of alternately wetting and drying pre-biotic materials on sea shores (possibly on clays with large effective surface areas.) The dryer and variable climate of earlier Mars might have provided an alternative life producing environment.

Garth
 
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BTW my favourite photograph by Curiosity of Gale crater is this one:
marsgale_curiosity_1452.jpg


You can just see, almost straight ahead, the road winding its way down the crater wall..... ;)

Garth
 
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marcus
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Garth, I did not know about the Goldschmidt conferences on geochemistry.

Please explain more about the chemical conditions for RNA to be produced abiologically, if you feel so inclined. I am stunned by the unfamiliarity of some of this, but curious.

Apparently the boron and/or molybdenum minerals need to be in an OXIDIZED state, in order to stabilize or serve as templates. The early earth had a reducing atmosphere, that seems to be the catch.

Too much water and not enough oxygen.

I can begin to picture how RNA might have been synthesized on Mars, assuming it had an oxidizing atmosphere and semi-arid conditions with occasional pools of water that would periodically dry up.

On the other hand I find it very hard to imagine how RNA once synthesized on Mars could have been blasted into space by a meteorite collision and carried to Earth and survived the trip. Have to go, errands back later. Explain anything you feel like its new and kind of dizzying in parts.

Make it as basic as you want, other people besides me might be interested. I recall boron makes many different complicated oxides, not just one type. Is that right? That might be relevant. But a methane atmosphere might "reduce" minerals by gobbling up their oxygen---stealing it from the boron or molybdenum minerals--and spoil the intricate scaffolding on which RNA could accidentally be built and preserved.

So you don't want a methane atmosphere, you want a CO2 atmosphere, with some oxygen in the mix. The oxygen would come from the UV in the sunlight breaking water into H and O and then the hydrogen escaping off into space. But already CO2 could be classified as "oxidizing" rather than "reducing". I'd like to hear more about how early Mars would be a better place than early Earth, for the formation of RNA.

One of the links you gave:
http://adsabs.harvard.edu/abs/2008AGUFM.B24C..01B
Elements and the Origin of Life
Abstract
The central paradox surrounding the origin of life is not presented by a scarcity of organic compounds (which are abundant in the cosmos), but rather the ease with which organic compounds become tar when they are exposed to energy. One emerging solution to this problem is the interaction of minerals with organic compounds in ways that not only guides their reactivity, but also stabilizes end products having biological value. One breakthrough in this area is the discovery that ribose, the "R" in "RNA", is formed in a guided process in the presence of boron-containing minerals, and is stabilized by boron once it is formed. This process may have been coupled with molybdenum-guided pathways on early Earth. These observations, confirmed in detail in the laboratory, are guiding those who model planetary formation to consider how these two elements, neither particularly abundant in the Earth's crust, might have been made available to organic molecules evolving early in Earth's history to give chemical systems capable of Darwinian evolution.

Here is the program of the 2013 Goldschmidt conference (at Florence that year)
http://goldschmidt.info/2013/program
Prof. Stephen Benner , who gave the talk described in Phys.org at that conference, was one of the authors of the "Elements and the Origin of Life" paper in the Harvard abstracts. Is that paper online anywhere?
Was there a followup presented at the 2014 Goldschmidt conference?
 
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Apparently they are required as templates for the formation of RNA, a precursor for life: Elements and the Origin of Life. Boron and Molybdenum.
The abstract just says those two elements can help. That does not mean they are necessary.

I forgot where I read that, but it was shown that quite complex things can survive getting ejected due to a meteorite impact (and landing on earth). Probably including RNA. Then we need something to replicate it, either on Mars (plus transfer to Earth) or on Earth (but then how did we get enough RNA on Mars to make a transfer likely?).
 
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marcus
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The abstract just says those two elements can help. That does not mean they are necessary.

I forgot where I read that, but it was shown that quite complex things can survive getting ejected due to a meteorite impact (and landing on earth). Probably including RNA. Then we need something to replicate it, either on Mars (plus transfer to Earth) or on Earth (but then how did we get enough RNA on Mars to make a transfer likely?).
Many serious questions need to be answered, certainly.
Garth may know if this is right: I think the researchers may focus on RNA because it is the closest thing to being SELF-replicating under the right conditions. is that right?
 
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Nobody knows how life first formed on Earth, the various papers on the subject - and my comments - are all hypotheses and educated guesses, but yes I think the formation of a simple form of RNA is thought to be an intermediate step.

Garth
 
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Couple comments/questions from a p-chemist with a geochemistry minor to "stir" the pot a bit.
Distinctive features
Not necessarily "unique," hence the hypothesis.
required as templates
those two elements can help
Other templates have been proposed/suggested/hypothesized --- as of 40-50 years ago the assays of the offered candidate mineral substrates may not have detected trace elements which could have effected the "life/proto life" chemistry. Still, mfb's observation that B and Mo can/might help is probably the safer working statement.
an OXIDIZED state
What's #3 in terms of cosmic abundance? Try telling me the universe is not oxidizing at the bottom of small local gravity wells.
 
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This is very intriguing, but as Carl Sagan said, extraordinary claims require extraordinary evidence. I'm excited to see what happens (and childishly hoping these are microbial mats!), but very skeptical.

Also bear in mind that when you have a hammer every problem looks like a nail to you. The author of this paper is a geomicrobiologist and so it makes sense she'd leap to a microbiological explanation of these structures; I'd like to see more research done on them by sedimentologists to look for alternative explanations.
 
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Very exciting, If some evidence of life is found it would be a huge shift, life found at least twice in one solar system would mean life is pretty common accident in the universe.
 
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Is there currently an alternate hypothesis?
 
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It's very hard to make RNA prebiotically, because of its ribose.

Prebiotic ribose synthesis: a critical analysis. - PubMed - NCBI by R. Shapiro, 1988
The discovery of catalytic ability in RNA has given fresh impetus to speculations that RNA played a critical role in the origin of life. This question must rest on the plausibility of prebiotic oligonucleotide synthesis, rather than on the properties of the final product. Many claims have been published to support the idea that the components of RNA were readily available on the prebiotic earth. In this article, the literature cited in support of the prebiotic availability of one subunit, D-ribose, is reviewed to determine whether it justifies the claim. Polymerization of formaldehyde (the formose reaction) has been the single reaction cited for prebiotic ribose synthesis. It has been conducted with different catalysts: numerous basic substances, neutral clays and heat, and various types of radiation. Ribose has been identified (yields are uncertain, but unlikely to be greater than 1%) in reactions run with concentrated (0.15 M or greater) formaldehyde. It has been claimed in reactions run at lower concentration, but characterization has been inadequate, and experimental details have not been provided. The complex sugar mixture produced in the formose reaction is rapidly destroyed under the reaction conditions. Nitrogenous substances (needed for prebiotic base synthesis) would interfere with the formose reaction by reacting with formaldehyde, the intermediates, and sugar products in undesirable ways. The evidence that is currently available does not support the availability of ribose on the prebiotic earth, except perhaps for brief periods of time, in low concentration as part of a complex mixture, and under conditions unsuitable for nucleoside synthesis.
Butlerov's formose reaction is essentially polymerizing formaldehyde. One needs a high concentration of it, and it has to be relatively free of nitrogenous contamination.

The low yields of ribose suggest that the reaction produces isomers of it almost indiscriminately, suggesting that ribose is not much more stable than its numerous isomers. As one adds formaldehyde monomers, the number of isomers increases exponentially. They differ in where the double-bonded oxygen is, either at the end (aldo) or in the middle (keto), and also in asymmetries of the asymmetric carbon atoms, those bonded to four different groups.

Asphalt, water, and the prebiotic synthesis of ribose, ribonucleosides, and RNA. - PubMed - NCBI, 2012 states
RNA has been called a "prebiotic chemist's nightmare" because of its combination of large size, carbohydrate building blocks, bonds that are thermodynamically unstable in water, and overall intrinsic instability.
though the authors speculate on prebiotic-synthesis mechanisms that could produce it.

These difficulties with RNA have made some biologists consider alternatives to a nucleic-acid backbone, like amino acids (peptide nucleic acids) or polycyclic aromatic hydrocarbons (PAH nucleic acids). Both small AA's and PAH's are relatively easy to produce prebiotically.


So while the RNA world is now well-supported, it looks like its RNA was descended from some other replicator. In fact, the origin of its RNA is the main criticism I've seen of the RNA-world hypothesis.
 

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