chrophy in mars? - life in mars

alokmohan · 2004-04-05 04:53:22

Do you know if mars has cholorophyl?

SBird · 2004-04-05 10:39:24

I think we can safely rule out the presence of large amounts of chorophyll on Mars. First, there are no large quantities of plants on Mars. Second, chloryphtll hasa distinctive spectral signature. If there were any decent quantity of the surfff on Mars, we'd have noticed it by now.

Shaun Barrett · 2004-04-06 05:40:46

There was some data from the Pathfinder mission which suggested there might be small patches of chlorophyll in the martian soil. It was obtained from a panoramic photo taken by the lander but it was never confirmed that chlorophyll was indeed the cause of the positive result.
Interesting though.

SBird · 2004-04-06 10:11:47

Do you have any details for that observation? I'd be curious about which instrument made the potential find. If it's the camera, I'd be highly sceptical - lots of stuff can look green. If it was the spectrometer, It would be a lot more solid - the spectrometer gives much more detailed compositional information.

If chlorophyll were discovered on Mars, it would implya very strong link between Earthly life and Martian life ata recent point in evolutionary terms. The reason is that MArtian life would have had no reason to develop chlorophyll. Plenty of different molecules will absorb incident light just fine. The probability ofa complex molexule like chlorophyll developing independently is almost zero.

atomoid · 2004-04-06 13:35:29

There was [http://news.bbc.co.uk/1/hi/sci/tech/1913228.stm]an article two years ago about chlorophyll being detected on the soil near Pathfinder.

Knowing the spectral signature of chlorophyll, the researchers wrote a computer program that systematically scanned the Superpan for any pixels of interest.
Specifically, the program looked for the spectral signature associated with red light absorption by chlorophyll. "
The articles goes on to state: "Close examination revealed that four of the cases occurred on the Pathfinder spacecraft itself. But two regions showed a chlorophyll signature in the soil around Pathfinder."

Well, a lot of things could absorb red light, but i'd assume the scientists would adjust for any such "known" scenarios, and mars dust being what it is, maybe noone knows... Also, the chlorophyll signatures on the lander itself would imply its blowing around with the dust. Could a complex molecule liek chlorophyll even survive the uv envronment on mars if it is indeed blowing around with the dust? i'd guess it would get broken down pretty quickly, but im not a biochemist... its interesting that 2 years have passed since this story was released and we've heard nothing more abou tit, does this mean there was nothing to report (maybe they found out their method was flawed and there was really no actual chlorophyll signature (and of course didnt bother to report their failure to the media (and not that the media would tend to pass such a non-story along to us anyway...(but i digress (or it that regress? (or nested regress?)))))) or are they still working on it? who knows?
maybe its all a gov't cover-up! )

however, I would'nt discount the possibility of chlorophyll evolving completely independently from Earth, it seems like a good efficient method for life to use, and life found it pretty early on in the scheme of things, so maybe its an obvious solution, since if the tools and raw materials are similar it follows that a similar, maybe even duplicate, solution might be probable. I guess im saying i enthusustically entertain the idea of convergent evolution, just like the eyes of humans and squid evolved from completely separate trees to become very much similar (form follows function), you could have chlorophyll evolving on Mars to be pretty much like earth chlorophyll, and im not sure, but is all chlorophyll on earth share a common ancestor? either way, it appears life has had no reason to change the chlorophyll moleclue since it seems to be a good solution and does its job just right, no need for a different kind of molecule that takes over the role of chlorophill even though there would seem to be plenty of niche circumstances and opportunity for divergent types of it to arise on earth (maybe there are differnces that im unaware of, the point is whenever you need a way to get a spare electron from sunlight, the right molecule for the job always ends up looking pretty much like and has essentially the same properties of -you guessed it: Chlorophyll).

Shaun Barrett · 2004-04-07 02:02:25

Many thanks, Atomoid, for your timely assistance with the chlorophyll article. That's exactly the data I was referring to.
(Things have been tricky for me lately due to travel commitments; I'm only able to access a computer sporadically. Sorry if I'm not keeping up with things. :bars: )

SBird · 2004-04-07 11:00:29

I'm dubious. 4 of the 6 chrolophyll 'hotspots' that the spectrometer found were on the rover itself. Unless you posit that some sort of space moss started growing in significant quantities on Sojourner, this is a highly questionable result. This smells like experimental noise to me. Of course, it's a possibility but a faint one at that.

Chloryphyll is by no means the only light absorbing material available. There are actually many different varieties of chloryphyll as well as numerous other power-generating light absorbers. The chloryphyll is a highly complicated poryphrin with manganese in it. There is no particualrly good reason to use it other than it was the best molecule that evolution stumbled across. This doesn't mean that it's the best out there, far from it. Evolution goes toward the best local maximal solution, not the best global solution. That means the evolution tends to find what works well enough, not the best solution. If chroyphyll is actually present on MArs, it is a very strong sign that Earthly and Martian life share a very close evolutionary heritage.

John Creighton · 2004-04-07 11:13:44

Evolution goes toward the best local maximal solution, not the best global solution.

Maybe not totally related but in optimization (e.g. neural networks) evolutionary algorithms are used because they tend not to get trapped in local minimums as easy algorithms based on gradient decent (e.g. back propagation). The distribution of the mutation, (i.e. do we expect mutations to be close to the parent or far from the parent), can be tuned to optimize the algorithm for local searching or global searching. If the algorithm is optimized for local searching it may find the local minimums very quickly but it may take a long time to find the global minimum. Perhaps it will take longer then the age of the universe.

SBird · 2004-04-07 11:36:18

This is true in a controlled environment. For example, if one wants to alter the function of a protein through directed mutagenesis, it turns out that the best way is to use a ridiculously high mutational rate.

In natural evolution, that amount of DNA damage is instantly lethal. There are too many dependancies and critical functions that will be knocked out for evolution to make many large solution space jumps.

atomoid · 2004-04-07 18:01:10

This is true in a controlled environment. For example, if one wants to alter the function of a protein through directed mutagenesis, it turns out that the best way is to use a ridiculously high mutational rate.
In natural evolution, that amount of DNA damage is instantly lethal. There are too many dependancies and critical functions that will be knocked out for evolution to make many large solution space jumps.

In regards to the possibility of finding Mars fossils (and therefore the life would have apparently necessarily been macroscopic and muticellular), it would have been necessary for Mars to have gotten much further along in evolution relative to the earth (since it appears wet conditions on Mars dried up billions of years ago).

Such a high (and lethal) rate of mutation necessary for that kind of quick evolutionary progression would seem to quickly make that possibility pretty much null. But im not versed in evolutionary theory and the abstract concepts are not quite set in my mind, so i ask (beg) the questions, maybe one of you can patch up the underlying assumptions here:

- What on Earth kept life from going multicellular for so long? What suddenly happened in that soup that made it okay for these forms to flourish, its not that the possibility hadnt cropped up before that? i would expect such possibilities to always be "in the mix" due to the random fluxing in the genepool, just not favored by natural selection. why not?

- What on Mars would pressure for such early adaptation of multicellular life? if the above is just an "Earth-case scenario" then maybe life elsewhere in the universe becomes muticellular earlier than it did on Earth. Is it prudent to assume that it should take billions of years for multicellular life to occur or is it always just waiting for the right opportunity (no pun intended)...

lunarmark · 2004-04-08 07:11:43

Darwinian evolution just doesn't completly add up in my book, why would any animal evolve eyes that don't work (They seem to have evolved 'duff' ones before working ones!) and the same is true with wings, I just dont subscribe to the one animal-mutated-one-day-and-survived-better-because-he -had-little-wing-like-stumps-on-his-arms,-and-these-turned-into-wings-over-millions-of-yea
rs-scenariao! - yeah right.

That aside the jump from single to multicellular biological systems is all very well, but why?

I guess it's ultimatley because different 'bacterial' systems formed a sybionic relationship, where it was benificial for many to work together, these communities then formed autonomous animals etc.

No, I think the enviroment on mars has never been 'earthlike' for long enough for anything other than a psuedo life chemical sludge, & we should get used to it.

Now Venus on the pther hand, - there would be the best place to look for simple life forms, plenty of chemistry still going on! and no ones looking!!

SBird · 2004-04-08 10:29:27

I'll try and answer both of your questions in one sweep. It's a mistake to think that evolution has a goal. Life is generally not getting more perfected. Often, you see evolution take two steps back for very one it takes forward.

The evolution of multicellular life is believed to be the result of a freakish case of symbiosis/parasitism. Basically, there was some sort of large microbe that ended up attemptin to eat or being paracitized by other bacteria. The end result was a communal organism. Mitochondria, chloroplasts, plasids and possibly golgi bodies and even nuclei are the result of this process. These new creatures were more complex and ended up forming agglomerations like Volvox and slime mold after a while. Eventually, some gene duplications occurred and the resulting organism was able to start working as a larger organism with specialized tissues.

These larger, multicellular organisms had the primary advantage that they can eat smaller organisms. Since size is a large determining factor of what can eat shat else, higher organisms have been trying to to-up each other in terms of size ever since. The problem, though is that larger organisms tend to need much more in the way of resources and are therefor extremely vulnerable to mass extinctions. If you follow the maximum size of creatuers, it follows a sawtooth pattern where mass extinctions knowck it back down and it starts its slow climb back up again. Being complex and larger is nota good strategy for long term survival. The only advantage to being multicelular is that it allows you to fill previously unoccupied ecosystem niches that were previously unavailable. The only unequivocal advantage to being multicellular is the creation of human intelligence which has allowed the sidestepping of standard evolutionary pathways.

Given the random way that multicellular life came to be on this planet, one can infer that it's really impossible to say how quickly it might have arisen on an alternate Earth or another planet. It might have just as easily happened a billion years earlier or later.

The same can be said for intelligence. Human level intelligence appears to be a rare adapataion. Wings have evolved at least 4 seperate times in the period it took for us to get smart. Although the root mechanisms for human intelligence are porrly understood, it is clear that sheer neuronal quantity is not a requirement - big brains do not equate being smart. This is shown by the anamalously high intelligence of certain bird species with low brain/body mass ratios and people with congenital birth defects that cause their brainsto be up to 10 times smaller than normal - these people end up being relatively normal in intelligence.

It is clear that human intelligence is more closely tied to the way the neurons are wired up rather than the sheer number of them. Therefore, human intelligence is similar to multicellular life - a stochastic event that could have happened much earlier or later. There is no particular reason that intelligent life on this planet couldn't have appeared 200 million years ago. There is no particular reason why it couldn't have never occurred at all.

SBird · 2004-04-08 10:40:38

Actually, the evolution of eyes is fairly straightforward. Everything from light sensitive cells to a full-fledged eye can be traced through a set of progressions that add progressivly more and more functionality. The evolution of wings is more problematic but largely complpicated by the fact that we really don't know exactly how transition creatures like archaeopterix lived.

Evolution is one of the most strongly experimentally supported theories in science. Although it's still possible to quibble over some macroevolution points like the formation of wings and timeline details, the evidence for evolution is incontrovertible these days. It's supported by a large fossil record, molecular biology evidence, and actual quantitative study. Read The Beak of the Finch by Jonathan Weiner. It's a scientist's account of a multi-decade research effort on the Galapagos islands to quantify evolution. The study succeded brilliantly (along with many other studies inspired by it) to show that life rapidly changes characterisitcs to match the environment. The biggest suprise is that significant levels of adaptive chance occur over small time scales. The gradual changes that are seen in the fossil recod are more of a record of slow climactic shifts than an idication of how quickly evolution can operate.

atomoid · 2004-04-09 02:34:05

The biggest suprise is that significant levels of adaptive chance occur over small time scales.

So if multicellular life, intelligence and other such evolutionary-rut side-stepping advantages tend to always be propogated by latent contingencies within the mutation flux of the genotype (they just have to wait for the right conditions to flourish), then the intermittent changes along the way should crop up with perhaps somewhat rapid stochastic frequency, yet only to be repeatedly thwarted by being diluted in large genepools or nullified by an unfavorable selective environement. Therefore there is probably no good evolutionary reason to rule out the possibility of multicellular life on Mars very early on in its history. It may be unlikely, but if the Mars environment coupled with small genepools allowed such changes to propogate, and conditions selected for it, then evolution on Mars could have moved along very quickly indeed. So its really not entirely out of the question that there might be macroscopic fossils on Mars... (i was tending to assume a sort of slow progressive ascent of complexity andMars just didnt have nearly enough "quality time" for multicellular life to ever come about, not that i expect it has, but im crossing my fingers)

So the environment changes, populations plummet thus shrinking the genepool and making any new mutations statistically relevant, that when favorable, change the genotype very rapidly.
...do adaptive stresses or other forces somehow increase the actual rate or quality of the mutations themselves?
...or is it merely that the same old normal (or almost normal) mutations are much more influential due to their newfound statistical relevance?
...or maybe the mutations get factored into a feedback cycle where the diversity of the mutations feeds into the increased frequency of them, and this syngergistically peaks both the change rate and diversity value higher?

dicktice · 2004-04-09 08:55:52

SBird: I love the way you always seem to bring topics around to the evolution of "intelligence," quite aside from thinking, imagination, consciousness, self-awareness and all that. What your last (8th April) one expressing surprise at rates of evolving features made me suddenly aware of was: In all the million or so years of dinosaur evolution, nothing akin to human intelligence developed. Makes one wonder. . . .

SBird · 2004-04-09 11:12:56

atomist - That's essentially correct. Most advantageous mutations are purely stochastic events. If they're evolutionarily neutral in normal conditions, they are much more likely to survive until they can come into play. However, most truly beneficial mutations usually involve some osrt of trade off and therefore are actually disadvantageous until conditions change to favor them.

The most important factor is the environment. Generally speaking, evolution comes to a standstill until new evolutionary niches open up either through climate change or new mutations. For example, if a general drying trend starts, causing desertification, all sorts of new niches open up and plants like cactii can now evolve. Alternately, some fairly minor evolutionary change can open up new sorts of niches.

The most dramatic example was the precambrian explosion. As soon as multicellular life evolved and developed the homeobox genes which allow for the differentiation of limbs, virtually all of the complex life we know of exploded onto the scene in under 5 million years. Basicaly, the homeobox genes are timing genes that determine what sort of limb goes where on a body plan. The cool thing about these genes is that they're very flexible - the homeobox genes that put arms and legs on us, the dozens of legs on a millipede and fins on a fish are virtually identical except for small tweaking. This allows the rapid development of different body plans very quickly. What happened is that larger animals suddenly appeared that could move about and eat other creatures. This was a completely unfilled niche - nothing like this existed at the time. Therefore, it was easy for non-optimal designs to survive.

It's a lot like the dot com era. For a brief time, as soon as a new business model opens up, all sorts of companies spring up. Some are good ideas like Amazon.com. Some are downright stupid like the idea of shipping pet food to people across the nation like pets.com. For that brief, shining year, everybody survives because of all the money (eg: food) they can basically suck up for free. Then the system crashes. The venture capitalists run out of money (over predation/grazing uses up the food and prey plants and animals develop defenses) and the laws of natural selection come down like a big hammer. As a result, you get the dot.bust and only those few companies that actually had what it takes, survive. Analagously, all those bizzare spine covered, tentacle legged worms and swimming vacuum cleaners of the precambrian explosion only exist today as old fossils. The result is that jellyfish, crustaceans, worms, echinoderms and primitive fish all basically came into existence in a few million years. The old diagrams of sponge -> worm -> crustacean -> echinoderm -> fish gradually evolving are way off. They all showed up in a huge burst of evolution because for a short period of time, any wacky mutant found it easy to survive.

After the crash, things were very different. Now resources are in short supply and you have to compete for them. Species that can monopolize a particular niche are very stable indeed. The horseshoe crab has been around vitually unchanged for 700 million years. It found a niche during the precambrian explosion and has steadfastly held onto it ever since. Have other animals evolved since then that could have used the same niche (food, predator evasion techniques, shelter, spawning areas, etc) and donea better job? Probably. However, they're going against an entrenched foe and failed. Again, a business analogy works well. Imagine a small computer firm develops a new OS that is much better than Windows. Is that company going to displace Microsoft? Most likely not. The new mutants might be better adapted than the horseshoe crab for that niche but they're a small group of animals or even a single individual that are reproductive misfits because of their differences and small in number and they just die out.

You see this pattern repeated over and over - the colonization of land is another example. Alternately, mass extinctions do the same. What you see is that evolution starts to get stagnant over time - what survives tends to be modifications of what's already there, not new creatures. The dinosaurs, for example were basically just variations of big, dumb and mean for 150 millions years. Then the meteor hit and wiped them out. The mammals (which had actually evolved first and just weren't as evolutionarily well equipped) then refilled all those newly emptied niches with all sorts of new wierd designs like armadillos and elephants.

As for changing mutation rates, there's good evidence in bacteria that when food runs out, the mutation rate goes way up. Basically, the bacteria hit a potentially lethal mutation rate since they're starving anyway and it gives a tiny chance of finding an evolutionary workaround before they die. To my knowledge, no such system occurs in higher animals because of the longer reproductive periods.

dicktice - I'm fascinated by the evolution of intelligence because I'm deeply interested in the mechanism by which it works and also interested in how likely it is to exist on other planets.

As for intelligent dinosaurs, here's my take. Lots of times, evolution paints iteself into a corner. For example, plants are very inefficient. This largely due to the poor performance of the enzyme RuBiSCO which captures gasseous CO2 and allows the plant to convert it to useable carbon. It is a very slow, inefficient and non-specific enzyme. Currently, vast resources are being directed towards getting this enzyme more efficient because of the huge beneficial effects of increasing photosynthesis efficiency in food crops. All plants use this enzyme and it's pretyy clearly a case where evolution developed someting that barely worked and now plants across the planets are stuck with it. It's as optimized as much it's basic design will allow it to get and plants can't evolve a new enzyme to replace t becasue RuBiSCO is tied up in all sorts of complex regulatory and feedback loops that are essential for plant survival. The planet's biosphere could be radically different and more productive if the original CO2 fixing enzyme had been different.

Likewise, it appears that very specific brain structures are required for intelligence. What if early dinosaurs lost some minor brain structure to make room for larger heat exchangers in their noses? Basically, kiss intelligence goodbye. If that heat exchanger is important, it's highly unlikey to be lost so that another set of mutations can bring back that old brain structure. Alternately, perhaps dinosaurs were so successful because they evolved a new brain structure that made their brains operate more quickly, giveing them faster reflexes and that precluded the structures necessary for intelligence.

Alternately, who's to say that intelligent dinosaurs didn't evolve? If humans had never evolved industrialized society, the evidence that were were intelligent 65 million years from now would be hard to find indeed. Intelligence is not a particularly helpful development. There are lots of intelligent creatures out there like dolphins and grey parrots that really gain fairly minimal benefit from that brain power. Given a contest between a tiger and a 200 IQ person with no tools, my money's on the tiger. Intelligence only becomes successful with the advent of language and toolmaking. That requires other advantageous mutations that are quite unlikely to show up at the same time.

Furthermore, lets say that civilized bipedal dinosaurs did evolve. Nothing guarantees that they would industrialize. Human history until the last few hundred years has basically been a series of ups and downs as various societies rose and fell. It wasn't until both the science by deductive reasoning meme and progress for the sake of progress meme hit a rather undistinguished Europe a few hundred years ago that things finally took off. That didn't have to happen. If just a few things had gone differently, we'd still be living in grass thatched huts and herding sheep for a living today.

Shaun Barrett · 2004-04-10 00:28:13

A very interesting and thought-provoking post Sbird. I've always thought that the sudden explosion of multi-cellular life-forms about half a billion years ago was amazing. I know many scientists have attempted to find the trigger for it but I don't think there's been any real consensus so far. I think the availability of oxygen has been considered as one option.

Atomoid and Lunarmark, I would just like to throw in a gentle reminder about impact transfer of dormant life between the rocky planets of the inner solar system. It seems many people have a mental-block which somehow prevents them using this very real factor in their reasoning.
I don't think anyone knows for sure just how long clement conditions may have lasted on Mars; perhaps there were only brief sporadic episodes of balmy conditions or maybe there were much longer periods than we realise (I know studies of surface erosion tend to place tight upper limits on the duration of water-based erosion but the picture is complicated and not well understood as yet). But if life originated on Earth first, and there's reason to believe it didn't take long to do so, it was probably transferred to Mars over three billion years ago by impacts. Most people seem to agree that Mars was probably much more Earth-like at that time. Then, it just becomes a matter of how long Mars provided a suitable nursery for its development.
And how do we know a meteorite impact during that crucial Pre-Cambrian period didn't send to Mars, intact, some of that critical genetic information which resulted in the multi-cellular explosion we've mentioned? And who's to say that material didn't happen to arrive on Mars during a clement watery period which lasted a few million years? Maybe such a fluke of fate saw weird animals evolving on Mars at much the same time as they did here. Admittedly, the chances mightn't be good but they're not zero either! And I know that most of the life-forms which may have developed would have died when Mars re-entered one of its long 'ice ages', but perhaps some dug in (literally) and hung on ... who knows?

On the other hand, NASA's Dr Chris MacKay has put forward the hypothesis that Mars may have 'settled down' much earlier than Earth did. The surface would have cooled more quickly because it's a smaller planet and life may have appeared as much as 4 billion or even, say, 4.3 billion years ago. Here on Earth, cyano-bacteria were producing oxygen for well over a billion years (~3.5 gya to ~2.25 gya), only to see it chemically combine with new supplies of reduced material produced by vigorous volcanism. It wasn't until volcanism gradually subsided, that the excess oxygen began to accumulate in the atmosphere, eventually leading to conditions which allowed many kinds of multi-cellular, oxygen-burning, energetic organisms to evolve.
Dr. MacKay postulates that, with a much more rapid reduction in volcanism on Mars, any resident cyano-bacteria (or similar photosynthesising organism) would have produced an oxygen-rich atmosphere much earlier than it happened here.
As SBird points out, evolution depends as much on propitious circumstances as it does on anything else. Perhaps Chris MacKay's hypothetical Earth-like Mars, very early in the piece, was a veritable hotbed of evolution and saw primitive animal life develop 2 billion years before it occurred on Earth!

O.K., O.K. ... there's more speculation here than at a day-traders convention!! :laugh: But I have to somehow justify my feint hopes that one of the MERs might still pick up a genuine honest-to-goodness macroscopic fossil!
:;):

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#1 2004-04-05 04:53:22

Re: chrophy in mars? - life in mars

#2 2004-04-05 10:39:24

Re: chrophy in mars? - life in mars

#3 2004-04-06 05:40:46

Re: chrophy in mars? - life in mars

#4 2004-04-06 10:11:47

Re: chrophy in mars? - life in mars

#5 2004-04-06 13:35:29

Re: chrophy in mars? - life in mars

#6 2004-04-07 02:02:25

Re: chrophy in mars? - life in mars

#7 2004-04-07 11:00:29

Re: chrophy in mars? - life in mars

#8 2004-04-07 11:13:44

Re: chrophy in mars? - life in mars

#9 2004-04-07 11:36:18

Re: chrophy in mars? - life in mars

#10 2004-04-07 18:01:10

Re: chrophy in mars? - life in mars

#11 2004-04-08 07:11:43

Re: chrophy in mars? - life in mars

#12 2004-04-08 10:29:27

Re: chrophy in mars? - life in mars

#13 2004-04-08 10:40:38

Re: chrophy in mars? - life in mars

#14 2004-04-09 02:34:05

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#15 2004-04-09 08:55:52

Re: chrophy in mars? - life in mars

#16 2004-04-09 11:12:56

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