life on mars

[Mental Avenger]

there is a high probability around 90 per cent that life does exist in mars. the joke at the moment and for some time is if you go there, stay away from the caves.

Based upon everything I have seen regarding Mars over the past two decades, I would say that the probability of life existing on Mars is about .000000001%, if that. There may be a .000001% chance that there was once some very primitive life on Mars, but I doubt it.

 

[dfjchem721]

Based upon everything I have seen regarding Mars over the past two decades, I would say that the probability of life existing on Mars is about .000000001%, if that. There may be a .000001% chance that there was once some very primitive life on Mars, but I doubt it.

You shouldn't be such a skeptic (like I used to be!!) about life on Mars, Mental Avenger. Mars has a solid iron and nickel core, meaning it almost certainly had a molten geo-dynamo shortly after forming, also probably about 4.5 bya. This would of course provide some magnetic field, and allow for a much greater atmosphere than exists today. However, an atmosphere is not so essential to abiogenesis as a molten core is. The latter is likely critical.

Since earth's life is estimated to have arose following completion of abiogenesis ca. 4 bya, Mars could have had a similar environment in its first billion years, or more. As most of those who have considered the conditions necessary for abiogenesis, the consensus belief is that life arose on earth in the deep oceans, near thermal vents along the bottom.

(You may know all this, but let's review it relative to Mars.)

There are several reasons why this is a favorable environment. For one, the thermal stability of the vents surrounded by large volumes of thermally stable water provide a prime environment for life to arise from complex chemical assemblies. It is a virtual certainty that a stable thermal environment, one that lasts for some millions of years at least, would be required for abiogenesis. You could not have significant changes in temperature if such an extremely complex chemical evolution into the first life forms is to be successful.

The vents are also a source for many chemicals, and chemical energy. Almost certainly the first cells must have used such chemical energy since photosynthesis is vastly too complex to evolve from scratch. Surely some more primitive life form must have given rise to such a mechanism through biological evolution.

So these conditions for abiogenesis giving rise to life on earth certainly could have occurred on Mars a long time ago. There is evidence of substantial water on Mars, and it would appear to have a great deal of it below the surface. I have always been a skeptic about life on Mars as well. But upon recent musings regarding the origin of life on earth, it seems not so unlikely after all. Life on earth probably took ca. 3.5 billion years before we got to complex forms. Mars would not have had that "luxury". But I would give it a higher probability than your low estimates. The probability that Mars formed a primitive biological community that could have lasted for maybe a billion years, parallel to earth's life is better than 1:100. This is based simply on the fact that it definitely happened right next door on earth, and is only an acceptable probability in Mars' very earliest phase(s). If it didn't happen soon after Mars' formation, it never would.

Finally, it's duration would have depended entirely on chemical energy to maintain viability, and would perish once the internal heat source died off. Difficult to imagine it developing photosynthesis (but possible), or even complex multicellular forms. One would probably need to evaluate ancient carbon deposits like graphite, etc. to provide any evidence for ancient life on the Red Planet.

 

[IG2007]

Great post dfjchem!

 

[Catastrophe]

You shouldn't be such a skeptic (like I used to be!!) about life on Mars, Mental Avenger. Mars has a solid iron and nickel core, meaning it almost certainly had a molten geo-dynamo shortly after forming, also probably about 4.5 bya. This would of course provide some magnetic field, and allow for a much greater atmosphere than exists today. However, an atmosphere is not so essential to abiogenesis as a molten core is. The latter is likely critical.

Since earth's life is estimated to have arose following completion of abiogenesis ca. 4 bya, Mars could have had a similar environment in its first billion years, or more. As most of those who have considered the conditions necessary for abiogenesis, the consensus belief is that life arose on earth in the deep oceans, near thermal vents along the bottom.

(You may know all this, but let's review it relative to Mars.)

There are several reasons why this is a favorable environment. For one, the thermal stability of the vents surrounded by large volumes of thermally stable water provide an prime environment for life to arise from complex chemical assemblies. It is a virtual certainty that a stable thermal environment, one that lasts for some millions of years at least, would be required for abiogenesis. You could not have significant changes in temperature if such an extremely complex chemical evolution into the first life forms is to be successful.

The vents are also a source for many chemicals, and chemical energy. Almost certainly the first cells must have used such chemical energy since photosynthesis is vastly too complex to evolve from scratch. Surely some more primitive life form must have given rise to such a mechanism through biological evolution.

So these conditions for abiogenesis giving rise to life on earth certainly could have occurred on Mars a long time ago. There is evidence of substantial water on Mars, and it would appear to have a great deal of it below the surface. I have always been a skeptic about life on Mars as well. But upon recent musings regarding the origin of life on earth, it seems not so unlikely after all. Life on earth probably took ca. 3.5 billion years before we got to complex forms. Mars would not have had that "luxury". But I would give it a higher probability than your low estimates. The probability that Mars formed a primitive biological community that could have lasted for maybe a billion years, parallel to earth's life is better than 1:100. This is based simply on the fact that it definitely happened right next door on earth, and is only an acceptable probability in Mars' very earliest phase(s). If it didn't happen soon after Mars' formation, it never would.

Finally, it's duration would have depended entirely on chemical energy to maintain viability, and would perish once the internal heat source died off. Difficult to imagine it developing photosynthesis (but possible), or even complex multicellular forms. One would probably need to evaluate ancient carbon deposits like graphite, etc. to provide any evidence for ancient life on the Red Planet.

Another excellent summary.

 

[Mental Avenger]

You shouldn't be such a skeptic (like I used to be!!) about life on Mars, Mental Avenger. Mars has a solid iron and nickel core, meaning it almost certainly had a molten geo-dynamo shortly after forming, also probably about 4.5 bya.

Ok, good points. Therefore I will revise my estimates IMO, the probability of life existing on Mars is about .00000001%. There may be a .00001% chance that there was once some very primitive life on Mars.

 

[dfjchem721]

Ok, good points. Therefore I will revise my estimates IMO, the probability of life existing on Mars is about .00000001%. There may be a .00001% chance that there was once some very primitive life on Mars.

Well, at least you have increased the odds by an order of magnitude.

That beats dropping them based on my observations!

 

[Catastrophe]

Would this suit yo as a reasonable summary?

Around the time Earth was forming, parallel activity may have taken place on Mars.
Because of differences between Earth and Mars, the development may have been faster on Mars, but also resulted in ending earlier. For example: Substantial loss of atmosphere. For these reasons, though not impossible it seems very unlikely that any form of life developed.

Please shoot away!

 

[dfjchem721]

It would seem, based on all that is practical and required to abiogenesis, that any planet with a hot molten core, surrounded by a mantle with an ocean of salty water on top of that, could give rise to life.

The primary requirements on any planet almost certainly include long-term thermal stability of a large body of water, and which cannot escape into space. As noted before, thermal stability (likely in a narrow range), for long durations must be required for the origin of life. Any excursions outside this fixed temperature range would likely terminate abiogensis, or any of the earliest life that has already developed. It is reasonable to assume that life arises in a liquid environment (as the only likely scenario), since "solid state" or "gaseous" abiogeneis seems highly improbable.

And this water also must contains the necessary elements and molecular components on which abiogensis and the continuation of life is required. It stands to reason that most planets would have a large number of the elements for life - it is their abundance and availability that would be most important for any given planet to qualify for abiogenesis to initiate and become successful.

Finally, the Goldilocks temperature zone for abiogenesis to occur is not simply liquid water, but a narrow temperature range at that, which likely lies between ca. 20 and 60 degrees C. This temperature range was chosen primarily due to the sensitive nature of many biochemicals. Too hot and many will decompose, or react in ways detrimental to life. Too cold and the reactions move too slowly for abiogenesis to kick-start. Once life has gotten started, biological evolution could allow numerous forms of life to move into more extreme temperature zones, both hot or cold (as seen on earth).

The "activity" of water must play a major role, which is why the temperature range must be limited. Activity of an element or compound, in an aqueous phase, refers to its rotational, translational and vibrational energies, all of which impact the interactions and reactivity between all chemicals in solution. It is essential to appreciate that the activity of water drives the formation of membrane structures, and the folding of globular polymers, etc.. The driving force for this is entropic, to minimize the energy state of highly organized macromcoleular structures and assemblies. (Minimizing their energy states also maximizes their stabilities, a invaluable characteristic of membranes and biopolymers.) Activity of water also is essential in the many reactions involving water - primarily the hydrolysis of many compounds - reactions absolutely essential to all life forms.

Given sufficient time, life seems likely in a lot of places. How long it will survive depends on numerous other factors.

In short, if you meet these basic criteria for abiogensis and the origin of life, it could possibly evolve on any planet in the universe, so long as extremes such as radiation etc. do not interfere with the delicate chemical interactions required for abiogenesis and the continuation of life that arises from it.

 

[Catastrophe]

dfjchem721
Thank you for that long and highly respectable exegesis.
I have the greatest respect for your knowledge in this area but I would ask where, within the confines of an attempted summary, I have been inaccurate or have made serious omission(s). My objective was just to bring an agreed conclusion. Please just alter my summary - hopefully by making the minimum essential changes.

 

[dfjchem721]

Would this suit yo(u) as a reasonable summary?

.................For these reasons, though not impossible it seems very unlikely that any form of life developed.

Please shoot away!

As noted in my last summary, it would appear that for life to arise anywhere, the chemicals, heat source and an aqueous environment are critically required, all in a stable configuration one might find with an fairly large body like earth, venus, mars, and even so-called "super-earths".

Your comment that "it seems very unlikely that any form of life developed" cannot be corrected or changed as it may very well be true. There is no guarantee that the essentials all played out on Mars in its early years. While it is an opinion, it is your opinion. And meshes with Mental Avenger, who also gives it a low probability.

However, based simply on opinion and a bit of supposition due to its co-formation in the same solar system, it seems more likely to me that life could have arisen on Mars in its ancient past.

We are both talking about probabilities. You are as welcome to your odds as I am to mine.

 

[Catastrophe]

As noted in my last summary, it would appear that for life to arise anywhere, the chemicals, heat source and an aqueous environment are critically required, all in a stable configuration one might find with an fairly large body like earth, venus, mars, and even so-called "super-earths".

Your comment that "it seems very unlikely that any form of life developed" cannot be corrected or changed as it may very well be true. There is no guarantee that the essentials all played out on Mars in its early years. While it is an opinion, it is your opinion. And meshes with Mental Avenger, who also gives it a low probability.

However, based simply on opinion and a bit of supposition due to its co-formation in the same solar system, it seems more likely to me that life could have arisen on Mars in its ancient past.

We are both talking about probabilities. You are as welcome to your odds as I am to mine.

"We are both talking about probabilities. You are as welcome to your odds as I am to mine."
The difference is that you are more likely to be right

I suggested (albeit in my relative ignorance)
" For these reasons, though not impossible it seems very unlikely that any form of life developed."
If we change it to:
" For these reasons, though perhaps improbable, it seems a distinct possibility that some form of life developed."
I am not negotiating. I am requesting your superior decision. Please feel free to modify further.
I am not "on either side". I would just like to see a negotiated settlement.
If I were "on the other side" I don't think I could argue against that.

 

[dfjchem721]

There certainly are some intangibles that one could not be aware of based on these thought experiments. Some which are absolutely required for the completion of abiogenesis and its successful conclusion into the first reproducing cells, and its further evolution.

One of these is the relative abundance of various elements on a given world. There seems little doubt, for one intangible, that life requires a number of different ions to get going, at the very least. (Don't even think about all the organics required.) We use so many elemental ions, they are ubiquitous throughout biochemistry and physiology.

The ions of Na, K, Ca, Mg, Mn, P, etc. were and are used in the earliest manifestations in life, and it probably would not have existed without them. But do they need to exist at just the right concentrations for life to arise? It seems likely that there would be a limit to their variability range. Sodium and chloride are the most frequently used ions, but perhaps because they were the most common.

The chemical constraints may make for some difficult problems for Mars alone. We have no idea if it had ancient oceans, and if it did, are its ion concentrations similar to earth, or lacking in some major ones. Even a 50% loss of dissolved calcium could be deadly for all we know about abiogenesis. Calcium is huge in biochemical reactions, and also to neurological responses. This involves inter-cellular communications. The element is also used in contractile components, like muscles, etc. Just one element out of whack could result in failure of the initiating chemical evolution. And of course phosphorous is essential for RNA and DNA, without it you are going nowhere fast.

One cannot rule out the need for critical elements and molecules for the origin of life within a given planets oceans. So that is only one variable. Incidentally, you mentioned Mars not retaining an atmosphere long term due to the loss of its molten core. An atmosphere of any kind is not a requirement for life to arise in deep oceans. What is required is that the water is not lost to space as long as there is a enough core heat to power biological mechanisms.

And a surface is also likely required for abiogenesis, and silicates are the most likely suspect. These seem rather common on rocky planets, but maybe a precise surface is only found on certain planets. Again, the list of intangibles is significant.

Let's see if you can think of other constraints. You have experience in surfactants and miscelles.

 

[Catastrophe]

dfjchem721
(How on Earth did you think of that handle? Can't we call you dj or something shorter just in replies?)
There is so much to digest here, even for an 'ordinary' chemist or that lesser species of chemical engineer.

"The chemical constraints may make for some difficult problems for Mars alone. We have no idea if it had ancient oceans, and if it did, are its ion concentrations similar to earth, or lacking in some major ones."
From what I see in the magazines and on line continually the Mars water channels and ancient river beds are portrayed.

I believe from my lowly position that life just used what was there. If Na and Cl ions were important it was because there were lots of them. Our ancient predecessors collected twigs to light fires and thus survived cold winters.

As far as surfactants are concerned, of course you have your phospholipids and those wonderful side by side aggregates which form convenient barriers (I doubt many know what we are talking about) but (gosh - surfactants in the headline press) it is soap which solubilises virii (is that the correct plural?)

ASIDE:
"The verdict is: “The English plural of virus is viruses, not viri.” Merriam-Webster agrees, as does TheFreeDictionary. Wiktionary offers the following usage notes: The plural is often believed to be viri or even virii, but neither is correct Latin and both are neologistic folk etymology."
I don't remember virus occurring in my Latin GCSE O Level work.

I wonder if manufacturers of syndet bars are checking on solubilisation characteristics compared with 'real' soap? There is no guarantee they will work. Imagine bilayers in the skin composed of alkyl benzene sulfonates instead of phospholipids. The repulsion between the head groups would prevent bilayer formation. Good job Nature did not only have detergents from which to make life. Oh well, we would probably all be living in mixed micelles communicating with water-soluble TV sets.

In other words, I can't think of much use for surfactants other than the rather specialised ones which form bilayers.

Anyway, Sir, it is as always a pleasure to encounter you, and thank you for your above comments.

Chem. Eng. (Retired)

 

[akashrao]

very valuable contributions here, as i read through them ...

so to sum up on what went so far, the combination of inner fire and outer ocean and covering atmosphere that lead to abiogenesis on earth was absent on mars ...
or, it were also there on mars that somehow became extinct beyond recovery ...

so point 2 yields in to supposition that some life may have somehow survived, the chances of us finding it are low, quite way too low as pointed out by members ...

given earth-like conditions leading to abiogenesis, it is plausible that they may exist on exoplanets and why not
but for mars, unfortunately, not so much of luck!

what made mars lose its capability to host life is beyond our abilities to find because as a knowledgeable human race we are only some 5000 yo
what can be done if we wanna colonise mars lay in our hands today

do you believe that elon musk is gonna succeed in getting his plans through?
how many amongst us are really liking to settle on mars if musk is 100% successful ?!

 

[dfjchem721]

Cat, chem721 was an advanced course in organic reaction mechanisms I took back in grad school. One of the toughest courses ever. You had to think like a chess game, 6 moves ahead in three dimensions to get to the right reactions etc. And you had to show all the instruments you would use to deduce the reaction mechanisms for each step. Half the class dropped out after the mid-term. Gave me some insights on many other things. Call me dfj - that is close enough.

To all who have made other comments, some of the constraints on abiogenesis are clear - temperature, duration etc. But the intangibles make it so hard to estimate probabilities. Abiobenesis is right up there with the Big Bang in terms of deciphering the details. Since we can never see it happen, knowing all these intangibles is nearly impossible.

"The chemical constraints may make for some difficult problems for Mars alone. We have no idea if it had ancient oceans, and if it did, are its ion concentrations similar to earth, or lacking in some major ones."

The above is just one of the biggest problems when modeling probabilities of life on another planet, assuming the primary aspects are in place : rocky, molten core, long-term stability and lots of water.

As a result, it is simply impossible to estimate for any likely world, whether life can arise. No doubt there are people out there with better ideas than those presented here. They would be astrobiologists. I would guess they have some very difficult research!

 

[akashfedora]

therefore life is impossible on mars and colonization is ...

 

[Catastrophe]

therefore life is impossible on mars and colonization is ...

What are we talking about here?
Humans. Terraforming is impossible, colonies are not.
Humans and Martians. Martian life is impossible but we could colonise.
Sorry. I don't know what you intend to convey.

 

[akashfedora]

right, i stand corrected ...

 

[akashfedora]

mars revolves around the sun ... what is the force of attraction or centrifugal force b/n mars and sun and what is the centripetal force of mars flight that makes it orbit ...

 

[Catastrophe]

right, i stand corrected ...

Not trying to correct, just to see what you want to know

 

[Kakasnarta]

I think its highly likely that life of some sorts still exists on mars ,maybe only microbiology or deep underground in caves with water trapped for millennium.
But I think at some point in the past history of mars when water flowed and deep rivers ran over the surface.then life would have evolved ...and one day this will be proved without doubt.

 

[Catastrophe]

I think its highly likely that life of some sorts still exists on mars ,maybe only microbiology or deep underground in caves with water trapped for millennium.
But I think at some point in the past history of mars when water flowed and deep rivers ran over the surface.then life would have evolved ...and one day this will be proved without doubt.

Well, that is your opinion and you are entitled to it. Some will agree on one or some or all points and some will not. I am fairly open on some parts of the question, but do not like the without doubt comment. could have = possibly? would have = doubtful.
I recommend you to the posts of dfjchem721 for whom I have the greatest respect on this question.

 

[dfjchem721]

Well akashfedora, I don't know about your prediction that it is "highly likely that life of some sorts still exists on mars", but life within Mars today is far from impossible. Based on my latest review of the geology of both current and ancient Mars, some life forms could indeed still exist in subterranean refugiums. It is the probability that is so difficult to predict. And a molten "core" providing heat to the planet is still operational!

Much has been made of the need for a hot molten core to provide heat, nutrients and chemical energy for abiogenesis and the continuation of life on any planet (in the absence of photosynthesis). Many have assumed the core cooled off billions of years ago when Mars lost its geodynamo. Without it, a magnetic field to protect the atmosphere and surface from intense solar and cosmic radiation would not exist.

As it turns out, the data indicate that there were two molten forms of Mar's initial core. One, the inner core, is now believed to be solid, and produced the early magnetic field. Data from orbiting spacecraft detecting magnetic fields on the surface indicate that only ancient craters are magnetized, and younger ones are not. These results appear to date the loss of the geodynamo at around 4 bya, or ca. 500 million years after the planet's formation.

However, data obtained from numerous orbiting spacecraft have allowed scientists at the Goddard Space Flight Center* to assemble an image of Mars' interior by measuring the tiny changes in the Doppler shift of their transmissions back to earth as they orbit the planet. These data confirm earlier results which indicate that Mars still has a molten outer core (surrounding a solid inner core). With an estimated temperature around 1500K, this extensive outer molten core is hot enough to provide the heat and geothermal synthesis of those essential metabolites required for abiogenesis and continuation of Martian life, even today! That does not mean there ever was life on Mars, but only that the conditions to allow life to arise and persist still exist. Which is quite remarkable in itself. I always thought NASA has been pushing the notion of "life on other planets and moons" to attract public interest and funding, but it appears they have some pretty strong evidence to look for it!

These observations eventually led me back to the Curiosity rover data in Gale Crater**, which found unequivocal evidence for surface water on Mars long after the geodynamo was supposed to have died. Gale Crater is ca. 100 miles in diameter and was formed about 3.5-3.8 bya. Curiosity has a very appropriate name based on the results obtained so far. NASA landed Curiosity in 2012, in an area of Gale Crater that appears to have had liquid water flows on its surface. Data from this location indicate it certainly did. From the wiki site**:

"On June 1, 2017, NASA reported that the Curiosity rover provided evidence of an ancient lake in Gale on Mars that could have been favorable for microbial life; the ancient lake was stratified, with shallows rich in oxidants and depths poor in oxidants; and, the ancient lake provided many different types of microbe-friendly environments at the same time."

end quote

It should be appreciated that the data obtained from Curiosity is not speculative, but actual empirical evidence obtained by standard scientific methods, performed by robotic instruments, on the planet. This data beats speculation hands down.

Again, these observations provide undeniable evidence that lakes of liquid water existed on Mars surface for many millions of years, sometime between 3.3-3.8 bya. This appears to conflict with the magnetism data on the loss of Mars' magnetic field around 4 bya, assuming a strong magnetic field is required for long duration surface stability of such a volatile liquid as water.

Despite this apparent contradiction, there is no doubt that liquid water was very abundant on an early Mars, and evidence of expansive surface water is without question. So all of the requirements for life to have arisen on Mars around 4 billion years ago are still present today. While nothing is likely alive on the surface today due to radiation, it seems possible that life could have survived on the surface between 3-4 bya, and it certainly cannot be ruled out that subsurface life persists even today. It is all a matter of probability, and that aspect is clearly debatable.

It would appear that a number of surface robots will be needed in various areas on Mars if there is any chance of finding clear and convincing evidence of past life. No doubt evaluating evidence for life below the surface is a much tougher assignment.


* https://www.nasa.gov/feature/goddard/2016/mars-gravity-map


** https://en.wikipedia.org/wiki/Gale_(crater)

 

[akashrao]

okay