Mars Life Confusion

[CraigS]

I always thought NASA's search for life anywhere, was focused on looking for 'life-as-we-know-it', and the only 'life-as-we-know-it', is what surrounds us here on Earth.

So, the next rover mission to Mars is Curiosity, (scheduled for lift-off between 25 Nov to 18th Dec, this year). Its primary mission is to assess Mars' habitability and whether or not Mars has ever been capable of supporting microbial life. It carries a whole bunch of spectrometers and chemical laboratory instruments for detecting primarily, methane ... deemed to be a by-product of all life on Earth and hence, is the key indicator of Mars life.

Ok .. then this article about a recent study by the University of Florida/Space Life Sciences Lab at NASA's Kennedy Space Centre turns up today: Microbe risk when rover wheels hit martian dirt which basically argues that any microbes carried aboard Mars rovers, are unlikely to survive more than a few hours in the Mars' environment. I have read elsewhere that there are at least 13 separate factors on Mars that can kill Earth microbes (not counting Mars' perchlorate salts).

This infers that even the hardiest of 'life-as-we-know-it', can't live long on Mars.

So if this is the case, why are are they searching for organic compounds and methane by-products on the surface of Mars?

It would seem clear that we already know that 'life-as-we-know-it', cannot survive at, or near, the surface (from bio-physics)… so all this probe can do, is confirm what we already know … or uncover 'life-as-we-don't-know-it' !

So NASA is looking for 'life-as-we-don't-know-it ? .. this news to me, and the rover's design would seem to be a very, very desperate, fundamentally flawed way of looking for 'life-as-we-don't-know-it' !

I really hope they do detect something … if they did .. a manned mission would be inevitable ..

Cheers

[CraigS]

Ok .. so looks like they've tested a few earth-based extremophiles in trying to understand how they might fare under martian conditions.

This article says they tested one called 'Psychrobacter cryohalolentis', which thrives under extremely dry conditions and at temperatures as low as minus 10 degrees C. However, it didn't fare too well under the UV radiation to which it would be exposed on Mars. It normally lives in salt brine mixtures .. like what they've recently hypothesised might exist on Mars where trace liquid water might also survive for brief spells. (We had a thread about this just recently here).

It seems the conclusion to this one, is that if such an extremophile did exist on Mars, it might only be possible at depths greater than the top 10 to 20 centimetres.

Then there's the good old 'Bacillus subtilis' which survived on NASA's Long Duration Exposure Facility spacecraft for six years. It lived exposed to UV radiation of up to 3 times that of its original ancestors (it got its resistance courtesy of a DNA mutation). They sent some dormant spores of this up to the International Space station for 18 months, exposed it to hard UV and cosmic ray radiation. They came back in March of this year (not sure of the results yet, though).

So, on one hand they're saying that neither of these would be likely to survive on Mars' surface, through native hardiness or DNA mutation mechanisms. And it also looks like deliberate transplantation of our own hardiest extremophiles, is also not viable for colonisation purposes, (should anyone be thinking along those lines).

The conclusion here would be that they are eliminating panspermia mechanisms (from accidental probe contamination) which would be necessary, in the case where Curiosity does find 'life indicators' on Mars.

Which means they definitely are looking for Martians which emit earth-based-life-form biosignatures, even though they are expecting the life forms to be different from any earth-originating extremophiles. The model is very much centred on detecting organic based, purely martian DNA.

Very intriguing .. to say the least !

Cheers

[CraigS]

So, the model for the type of life they're looking for, is based on Earth's Archaea domain. These have no cell nucleus, or any other membrane-bound organs within their cells. They possess genes, and roughly similar metabolic processes to the more familiar Eukaryotes, (which posses complex structures, enclosed within cell membranes).

Archaea make use of a variety of energy sources like sugars, ammonia, metal ions, hydrogen gas or sunlight. Commonly they use CO2 to oxidise hydrogen. They don't photosynthesise. They reproduce asexually (no meiosis) and, (so far), none are known to produce spores.

So far, they've found them in lots of harsh environments, including the human gut. Their classification is based on ribosomal RNA sequencing. They contain only a single chromosome, and the smallest is estimated to have only 537 protein-encoding genes. They may contain smaller independent pieces of DNA. Probable cell fossil records date back to almost 3.5 billion years ago.

So, this is the model of life they've designed Curiosity to look for.
If archaea-like lifeforms are found, it would demonstrate that abiogenesis, (life originating from inorganic chemicals), followed Evolutionary/Natural Selection processes might happen in another habitable zone planet, other than Earth.

Would its discovery rule out Panspermia (via say meteor impacts) ?
This would seem to depend on the sub-type of archaea discovered, and how long it could possibly live in space, during transit.

But what if they don't find any bio-signs ? (This being basically, a higher percentage of biogenic C-12 bearing methane, over and above, non-biogenic C-13 bearing methane).

Does this then lead towards an evidence-based working assumption, that water-bearing planets, having life-supporting environments in the Habitable Zone, do not necessarily inevitably result in life ?

.. Now that would be a big conclusion !

Cheers

[xelasnave]

Thank for posting that Craig.
Excellent coverage and good reading.
alex

[CraigS]

Originally Posted by xelasnave

Thank for posting that Craig.
Excellent coverage and good reading.
alex

Thanks for the feedback, Alex .. its nice to know someone might be reading this thread !

Cheers

[CraigS]

So, I found the NASA Astrobiology website. This one hits the nail right on the head .. and gives an answer … right from the horse's mouth … the answer is from: David Morrison Astrobiology Senior Scientist, dated September 6, 2011 …

Question:
When astrobiologists say " life as we know it ", what does it really mean in the search for extra-terrestrial life? What would life as we don't know it be like?

There is no clear-cut meaning for "life as we know it". Usually this phrase refers to life based on DNA or RNA, probably also including viruses (although many biologists do not consider a virus to be alive).

Sometimes the meaning is expanded to include any life that us based on the same sort of water-mediated carbon chemistry (with amino acids & proteins) as we have on Earth, but with some other inheritance mechanism that does not use DNA or RNA.

Life as we don't know it would include life that some speculate could exist on Saturn's moon Titan where the temperatures are far below the freezing point of water but other hydrocarbons might, conceivably, form the basis for carbon-based life very different from that on Earth.

Astrobiologists are uncertain how we could recognize or detect life as we don't knew it, although presumably any life would use energy to change its chemical environment, thus perhaps providing clues to its existence.

You can learn more by looking up shadow biosphere:

http://en.wikipedia.org/wiki/Shadow_biosphere, weird life
http://science.howstuffworks.com/weird-life.htm, and synthetic life http://en.wikipedia.org/wiki/Synthetic_life

Cheers

[CraigS]

Again from NASA's Astrobiology website … and answered by: David Morrison
Astrobiology Senior Scientist, date: August 25, 2011:

Question:
I understand that you have found a life form in the Mono desert that can stand high levels of arsenic, and began to wonder if an arsenic, if not phosphorus, was used by it in its DNA. Could not this be a representative of the earliest life on Earth, and that in some point phosphorus came into the picture and the organism survived, and then another story began.

Phosphorus is one of a handful of essential elements for life as we know it on Earth. This element is part of the molecular backbone of DNA and plays a key role in the storage and transfer of chemical energy within cells. Arsenic has a similar atomic structure to phosphorus, but it is not important in biochemistry, and in large quantities it is a poison.

The experiments you refer to were carried out by a team led by Felisa Wolfe-Simon (NASA and U.S. Geological Survey). As summarized by Dennis Overbye in the New York Times:

"Seeking evidence that life could follow a different biochemical path than what is normally assumed, Dr. Wolfe-Simon grew [microbes from Mono Lake] in an arsenic-rich and phosphorus-free environment, reporting in the paper and a NASA news conference on Dec. 2 [2010] that the bacterium, strain GFAJ-1 of the Halomonadaceae family of Gammaproteobacteria, had substituted arsenic for phosphorus in many important molecules in its body, including DNA."

But the same article notes that critics have said that "the experimenters had failed to provide any solid evidence that arsenic had actually been incorporated into the bacterium's DNA."

This debate is still continuing in the astrobiology community. There is no question that arsenic was chemically incorporated into the bacterium. What is less clear is whether the arsenic actually substituted for phosphorus in functional DNA molecules. This is an important debate that will likely not be resolved for many months.

As Overbye wrote at the end of his article, "Only more data ... will tell whether the GFAJ-1 bug is weird life that has found a new way to live, or just tough and able to survive in arsenic." We need to understand the answers to these questions before we can profitably speculate about possible arsenic-based lifeforms. You can read more about this research on the NASA Astrobiology website here and here.

So, it seems that the 'evidence' for fundamental substitutions of base elements like phosphorus for arsenic in DNA sequences, is not necessarily agreed nor straightforward. So, the possibility of this permutation arising on Mars, doesn't look to be a straightforward 'given', either.

Cheers

[Shiraz (Ray)]

Hi Craig. Interesting thread

I guess no-one will know what forms of life can exist elsewhere till someone finds some. In the meantime, it probably makes sense to assume that they will be based on carbon, due simply to the unique chemical properties of that material. Apart from that, life-forms could have any structure, since, on Mars they could have had maybe 3 billion years to evolve in that totally different environment.

I doubt that minor issues like an increasingly toxic environment would make much difference to continuance of life once it got started - crikey there are bacteria in our hospitals that happily live in antibiotic environments that would have completely written them off only 50 years ago. Once life gets going it seems that you can't kill it with a stick - providing the environment changes slowly enough, it will adapt without even being aware of change. Our bugs might die on Mars, but the locals should be quite at home - if they exist.

Thus, since it is not likely that we can guess what forms life would take on Mars, the best starting point is to assume only that they will be carbon based and will require some form of water and energy. They will also produce waste and that is what I assume NASA is looking for - gas from decaying remains or alien crap. There may not be life in any form that we know, but any carbon life-form will produce recognisable waste.

Regards Ray

[CraigS]

Hi Ray;

Thanks for your comments - much appreciated.

Although most of us have been over this same ground a few times already, I was wanting to (kind of) document it all in the one thread, as the launch date for Curiosity is rapidly approaching. I believe this is the first time ever, that any space agency has actually gone looking specifically for life .. so I was also wanting to drill into exactly what it is that they're looking for from a 'what is currently known about life' perspective.

Expectedly, (I suppose), it seems to be a pretty sketchily defined mission objective. There's a lot that doesn't add up (for me) … but once again, somewhat expectedly, this is probably answerable by asking the question: 'how does one go looking for life as we don't know it'?

Along these lines for example, if they don't find anything … does this then mean, (in general), that life doesn't necessarily crop up on water-bearing planets, with similar age and composition as Earth, in 'habitable zones' ? I don't see how this conclusion would be easily avoidable … and it would have significant ramifications on our thinking about exo-life elsewhere in the universe.

It might also just deepen the mystery even further, but mishaps aside, this mission should give us information we haven't ever had access to … ever.

Cheers

[xelasnave]

Even if no trace of life on Mars it simply means we have not found anything on one planet..even if the signs are there we may not pick the right spot...and there are many more places to go both in our solar system and far far away.

But they will conclude something and as you observe Craig that is a step forward really.

It is interesting goggling re alien life (in general).

I turned up one of the guys who had been to the Moon declaring NASA is covering the truth and that they (aliens) are already here.... but so far there seems to be no evidence...which means they are covering something up by conspiracy theorists approach.

But that guy must be such an embarrasment to NASA.

I am not saying he is wrong but until I personally meet one ( an alien) I hold that this chap has lost it.

Craig a great review on the situation.

Your posts are always interesting and lead me to read a great deal of associated material..usually not that crack pot stuff...but its hard to miss it sometimes.

I was looking for an article I had read about some folk who are developing the methods for dealing with aliens (I thought it was on science daily )...I was going to post it but cant find it..happily

alex

[CraigS]

Originally Posted by xelasnave

Even if no trace of life on Mars it simply means we have not found anything on one planet..even if the signs are there we may not pick the right spot...and there are many more places to go both in our solar system and far far away.

Ok .. I've been thinking about this … the formation of the oldest extant surfaces on Mars happened 4.5 to 3.5 Gya. More recent geologic activity, (ie: lava flows), and the formation of Olympus Mons happened about 2.9 to 3.3 Gya. Mars is thought to have been impacted by a Pluto sized planet about 4 Gya. There is evidence that plate tectonics existed at the same time. The soil on Mars contains magnesium, sodium, potassium and chloride all these are found in garden soil here on Earth. Trace water is present on Mars, and maybe even huge amounts flowed in the past. Mars' atmosphere is more than capable of distributing surface based life (if it exists), as are the geological processes, and the movement of either frozen CO2, or water ice. There has been the same amount of time gone by to accomplish this same feat, as has happened for Earth.

On Earth, self replicating molecules are believed to have been produced about 4 Gya, and the last common ancestor of all life appeared about 3.5 Gya .. which is about the same time they think archaea also appeared (fossil record). The Moon was formed by the impact about 4.3 Gya. Water, ocean and atmospheric movements combined with plate tectonics and continental drift, have all played roles in distributing life evenly across the surface of the earth. Migration by species has obviously aided the distribution of life, also.

Both planets were subject to the same late-heavy bombardment 4.1 to 3.8 Gya.

My point here is that frankly, the composition of the environment, the atmosphere and geological history and age of Mars, is so similar to Earth's, (hence the life-distribution mechanisms are also similar), that if life is not easily found on Mars, then I really do think there is a case to be answered, and some serious rethinking about theories on what causes life to emerge, in what we presently call the 'Habitable Zone'.

Frankly, Mars looks to be the best bet, (certainly in our lifetimes), for detecting life, given our present life-emergence theoretical guidelines.

An explanation is definitely called for, if the outcome of Curiosity's experiments is: "no life signs detected on Mars".

I will personally find it very difficult to accept:

- "oh .. we didn't look in the right spot" or;
- "oh .. we didn't look on the right planet (within the Solar System)";

as nothing more than nonsense answers.

Ideas about going to other places in the Solar System, (or far, far away), are completely useless without an over-riding theory whose goal is to refine the search field options .. from a parent population of astronomical proportions.

Cheers

[CraigS]

Again from the NASA astrobiological website …

Question:
Finding life in the Solar System, ie on Mars, doesn't seem very likely any longer. So why not try and plant some life while we're there? The next mission to Mars (MSL/Curiosity) could carry a bunch of different hardy organisms to be spread in different promising locations. Is there any work being done along these lines?

Answer:
I am afraid that astrobiologists would challenge both your statement that finding life on Mars doesn't seem likely, and that we should consider transplanting terrestrial microbes to Mars. While we have not found life yet on Mars, each new piece of information seems to make the presence of life there more likely.

Most recently, the discovery of evidence for liquid brine near the surface (see my answer posted Aug 5, 2011) is the most positive information we have ever had about the potential habitability of the surface of Mars.

Even before this discovery, we had ample reason to expect aquifers of liquid water or brine beneath the martian surface. As long as there is any chance of a native martian biota, we have strong scientific and ethical reasons not to introduce any terrestrial life forms. For decades there have been international agreements to avoid biological contamination of Mars. Rather than intentionally introducing life from planet Earth, we have obligations to carry put our exploration of Mars in ways that minimize the possibility of such “forward contamination” of Mars http://en.wikipedia.org/wiki/Planetary_protection.

David Morrison
Astrobiology Senior Scientist
August 30, 2011

[mswhin63 (Malcolm)]

Hi Craig,

The last statement "Planetary Protection" is correct in all discoveries on Mars and other planets. To consider life "as we know it" formation of mars outside the Goldilocks zone and the formation of a magnetic field so many Gya are factors not determinable or not correlated in the information I have read so far. I don't have a lot of time to read though. (This is a point of interest not an argument).

[CraigS]

Originally Posted by mswhin63

Hi Craig,

The last statement "Planetary Protection" is correct in all discoveries on Mars and other planets. To consider life "as we know it" formation of mars outside the Goldilocks zone and the formation of a magnetic field so many Gya are factors not determinable or not correlated in the information I have read so far. I don't have a lot of time to read though. (This is a point of interest not an argument).

Hi Malcolm;
Thanks for your comment. I'm not quite sure I understand your point however, you have raised the water/magnetic field issue, and its impact on life.

So the story goes that "geological observations", suggest 'rivers and seas' of liquid water dotted the martian surface about 3.5Gya. The amount of water has been equated to a planet-wide ocean half-a-kilometer deep or more. For the planet to have stayed warm enough for liquid water, scientists assume that Mars had a greenhouse "blanket" of carbon dioxide atmosphere at least 1000 times thicker than what Earth has now.

That carbon dioxide is now mostly gone. So is the water. They either went up (the ions or neutrals reached escape velocity), or they went down (subterranian), or the 'geological evidence' is actually evidence of something else other than liquid water, (possibly CO2 sublimation runoff). If we assume water and CO2, and they 'went up', then the conclusion is that Mars' dynamo effect (giving rise to a once strong planetary magnetic field), must have ceased between 3.5Gya, and present day. (If they went down .. we'll find evidence of evolved life).

Accurate measurements of the present-day rates of loss of martian atmosphere have not yet been accurately determined, so they've got another mission called MAVEN scheduled for 2013.

If Mars did have 'big liquid water', it had it 3.5Gya, because this is what the geological observational evidence points to. This corresponds nicely with the right amount of time for life to have started, and thus supports finding life on Mars, from this era.

Once again .. if they don't find evidence of this life, then something has to give.

Either way ... both outcome(s) will be big news !

Cheers

[renormalised (Carl)]

Mars', environmental, atmospheric, geological and hydrological history was similar to ours very early on, but has deviated quite a lot since around 3.8Ga. Some of the mechanisms which promote the possibility of life look like they're still there, but the Mars of today is hardly anything like Earth is now, or has been for nigh on 3 or so billion years. Even back then, the fact that Olympus Mons and the Tharsis Ridge formed in the way it did shows that the geological (and most likely other ) processes were quite dissimilar to Earth's. Even on the broader scale.

[CraigS]

Take a look at this brief Youtube on the selected landing site, Gale Crater, for the Mars Science Laboratory/Curiosity rover.

Man, if ever there's going to be life found on Mars, its at this site !
.. Les Hiddens, Bear Grylls and Ray Mears would all scratch around this area looking for food and water if they were plonked on Mars !

Once again .. if they don't find it all in this place, then the rational conclusion surely must be "no life on Mars" and; "no life can be found in high probability 'Goldilock Zones"!?!

Cheers

[renormalised (Carl)]

100 times as thick as our present atmosphere, Craig, not 1000 times. Even given that the Sun was only 70% as bright then as it is now. Actually, even now, if Earth was placed in the orbit of Mars and it's atmospheric content of CO2 was raised to 1bar, we would have a stable and warm climate. The big problem with Mars is its gravity isn't sufficient to be able to hold onto such a thick atmosphere, given that the Sun, whilst not as bright, was more active in its early life and Mars lost its global magnetic field rather quickly due to its higher rate of cooling than the Earth. It also appears, from its average density (3.9gm/cm^3) that it contains considerably less heavy elements such as Fe and the radioactive nucleids that Earth has (even accounting for the increased density of the Earth due to gravitational compression of the body of the planet). It all contributed to Mars losing its atmosphere early on.

[renormalised (Carl)]

Originally Posted by CraigS

Take a look at this brief Youtube on the selected landing site, Gale Crater, for the Mars Science Laboratory/Curiosity rover.

Man, if ever there's going to be life found on Mars, its at this site !
.. Les Hiddens, Bear Grylls and Ray Mears would all scratch around this area looking for food and water if they were plonked on Mars !

I can just see it now, Les sitting casually by a campfire talking about the medicinal value of martian swap grass, Bear would be chasing down a martian antelope mouse for dinner and Mears would just be looking like his usual boy-like dumb self and fashioning a bow and arrow out of a piece of old martian driftwood

Originally Posted by CraigS

Once again .. if they don't find it all in this place, then the rational conclusion surely must be "no life on Mars" and; "no life can be found in high probability 'Goldilock Zones"!?!

Cheers

Not necessarily and actually a rather hasty conclusion based on very little evidence from one particular spot. It would be akin to landing in the middle of the Atacama Desert and then saying this planet has no life on it. The only way they're going to resolve this question once and for all is to go there and explore the place. A probe is only as good as what it's capable of doing physically and what it's been programed to do. The bugs might be hiding a metre or more under its deepest probes and it won't know they're there. They might even have neon signs flashing "Hi, we're here!!!" and it can't see much past the end of it's metaphorical nose, so to speak.

[CraigS]

Originally Posted by renormalised

100 times as thick as our present atmosphere, Craig, not 1000 times.

Yep I agree … however reference source is here and it says '1000' ... (blame Michael Schirber).

Cheers

[CraigS]

Originally Posted by renormalised

Not necessarily and actually a rather hasty conclusion based on very little evidence from one particular spot. It would be akin to landing in the middle of the Atacama Desert and then saying this planet has no life on it.

Quote from Wiki .. Atacama Desert

In 2008, the Phoenix Mars Lander detected perchlorates on the surface of Mars at the same site where water was first discovered. Perchlorates are also found in the Atacama and associated nitrate deposits have contained organics, leading to speculation that signs of life on Mars are not incompatible with perchlorates.

Interesting that you chose the Atacama as an example .. this is the exact model they've designed the MSL/Curiosity detection technology on.

The issue here is what the distribution of life may (or may not), be like on the surface of Mars. If life has evolved there, when say liquid water was supposedly 'abundant', then its primary distribution method was the liquid water (and wind, etc). Its dispersion in the immediate vicinity of Gale Crater should be fairly even .. if it emerged on Mars, based on what all our theories and models tell us, they should either (a) find it or; (b) not find it … otherwise why look there in the first place ?

So, if they don't find it, there must be some kind of definitive conclusion or statement .. and consequences therefrom.

Cheers