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rick sumner
Trad climber
reno, nevada/ wasilla alaska
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I consider it an impossibility that simple life doesn't exist on Mars. Subsurface, with scattered seasonal surface eruptions. The big question is the extent of complexity it once developed to.
To explore those possibilities and to develop technologies for transit to and successful colonization of; I for one would be willing to pay increased taxes for the R&D beyond the usual reach of private industry who seem to be the sector that has picked up the mantle of human extra terrestrial exploration and development.
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Brokedownclimber
Trad climber
Douglas, WY
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rick-
I agree with you for the most part; I'd probably use one of my Scientific Weasel Words rather than "impossible;" I'd go with improbable or highly unlikely. ;>)
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limpingcrab
Trad climber
the middle of CA
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I consider it an impossibility that simple life doesn't exist on Mars.
Why?
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healyje
Trad climber
Portland, Oregon
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As for the Earth being a "closed biosystem," all the water on the planet was brought here by cometary impacts in millennia past. We are continuously being bombarded, on a daily basis, by micrometeorites, and sometimes they reach the surface without being consumed by entry heat. There are huge meteorites in museums, and the interiors of these can be further analyzed. Mostly, they are Iron meteorites, containing lots of Nickel.
Clearly, but the point they are making is that Earth, and planets in general, are as close to working 'closed-loop' systems that we currently know of.
My primary reason for sending an expedition to Mars, is although we have sophisticated robotic laboratories being built, most experiments don't give true answers; they simply give rise to more questions. I know this firsthand, having worked in chemistry R & D laboratories most of my adult life. No matter how sophisticated we build the robotics, nothing beats the good old "Mark I Eyeball" directly on the scene.
No doubt, but at what cost? Experiments to date haven't been robust, direct tests for life, I'm guessing that's about to change in the next generation or two of planetary robotics.
Even the evidence of past bacterial or protozoan life forms on Mars would be HUGE! Ditto, checking out the subsurface oceans on Europa for bacteria, fungi, protozoans, etc. would, to me, be worth a lot of our national treasure...
I agree. I personally think life is unavoidable and common as snot and it would certainly be nice to have some proof of that conjecture within our local system. It would also be nice to have some DNA to evaluate the whole panspermia concept given I think that's also a viable and more realistic way to 'colonize' other planets and planetary systems.
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Ed Hartouni
Trad climber
Livermore, CA
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As for the Earth being a "closed biosystem," all the water on the planet was brought here by cometary impacts in millennia past.
While this is a favored hypothesis, it is not confirmed... and by "closed ecosystem" I believe that what is meant is that no extraterrestrial life is involved in the Earth's ecosystem.
Obviously, the energy provided by the Sun is necessary and external to the Earth's ecosystem. Also, the Earth's magnetic field is a major part of making the planet habitable.
And water is an essential ingredient which seems to have been around in some quantities from very early on, independent of the ecosystem (probably prerequisite to life).
Life on Mars? there seems to be no sign of it. If you look at Earth, probably the biggest signature is the oxygen in the atmosphere. The fact that atmospheres are in chemical disequilibrium is potentially the most likely means we'll have to see if life exists on planets circling around distant stars. Lovelock's 1965 paper "Basis for Life Detection Experiments" explored this in detail.
The paper is a generalization of the task Lovelock undertook for NASA to help design a set of experiments for the Viking landings. The experiment "B2 Atmospheric analysis. Search for the presence of compounds in the planet's atmosphere which are incompatible with a long-term basis. For example, oxygen and hydrocarbons co-exist in the Earth's atmosphere."
This is why the observation of methane in the Martian atmosphere elicited such interest. Of course, as Lovelock states, it alone is not a signature of life... that would require the existence of oxygen too, of which there is not much. The idea being that life could keep producing these things away from the nature chemical equilibrium state.
The devil's in the details, and in the intervening 50 years a lot has been learned. An interesting updating of the atmospheric gas signatures can be found here:
http://arxiv.org/pdf/1503.08249.pdf
Krissansen-Totton, Joshua, David S. Bergsman, and David C. Catling. "On detecting biospheres from chemical thermodynamic disequilibrium in planetary atmospheres." Astrobiology 16.1 (2016): 39-67.
You can see the available Gibbs energy for the Earth is an order of magnitude larger than for Mars (and Mars is explained in the paper).
That energy corresponds to the N₂-O₂-H₂O(l) disequilibrium (due to life). This corresponds to 0.7 TW (terrawatts) of biological activity.
Interestingly, human energy production is roughly 20 TW, and most of this is exploiting the historic biological activity stored in hydrocarbon reserves. So maybe this points to a possible signature of "intelligent life" on distant planets... additional disequilibrium affects of prodigious energy consumption.
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Brokedownclimber
Trad climber
Douglas, WY
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Although there are a lot of "plusses" involved for robotics, especially for Mars, the question that keeps popping into my thoughts is getting an adequate range of samples from a given mission. The robotic laboratory has certain apparatus designed to do only a limited number of tests, and that therefore, requires sample collection. Drawing any real conclusion regarding life on Mars, past or present, requires covering a huge range geographically. Since robotic laboratories are anything but very mobile, it seems to require a much more sophisticated sample collection method to validate the entire planet. Having pre-selected Mars landing sites is like shooting craps or playing roulette; maybe you win, but probably lose, especially collecting samples close by the robolab. My conclusion, no matter how expensive and "dangerous" it may be, a human presence is a necessity logically. The whole big burrito of the Mars expedition would be ~ 5% of the F 35 fighter boondoggle. I rest my case.
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Brokedownclimber
Trad climber
Douglas, WY
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Ed-
Your comments are always valuable and well-received by me; I had the caveat of looking for evidence of PAST life on Mars, since most astonomers now conclude that water was once plentiful on the planet and there was a substantial atmosphere--now mostly lost. Yes, the magnetic argument is still valid; it's just my curiosity that drives me towards a manned mission. I'm drawn to it, just as most of us here on the Taco are drawn to rock faces.
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Ed Hartouni
Trad climber
Livermore, CA
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I think developing the robotic exploration technology has a lot more positives in the long run. We do much remote sensing on the Earth to great benefit. It is perhaps the only chance we have of collecting the data of the entire Earth ecosystem.
I don't doubt that we could send humans to Mars, though it will not be easy, and it will not be without tragedy. But I wonder if it isn't all the better to continue refining and advancing the robots. There are many frontiers in science where we humans do not (and cannot) actually visit... our instruments do the work experiencing those worlds, and we interpret what the instruments experience.
When our instruments fall short, we design new ones better able to carry on the research.
Beyond Mars and perhaps Venus, it is not at all clear that we can overcome the challenges of deeper human explorations into the solar system. But certainly, our robotic explorers will go. Those same technologies have many terrestrial applications. I don't see an imperative to go to Mars at this time. And technologies get better, perhaps there will be a good solution in the future. I don't much care if they are Chinese astronauts landing on Mars, it would be glorious if the astronauts had no nations to affiliate to...
...but we can do more with less resources and have a broader outcome with the 'bots.
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healyje
Trad climber
Portland, Oregon
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Seems like it would be as difficult for humans as robots to pull off a planet-wide survey of Mars. Humans can't travel too far from their base I would suspect and can't stay out long whereas the rovers seem to go for an extended period and reasonable [local] distances with little limitation on their working hours. I get the fun part of going, just not sure the cost and risk is justified relative to robotic missions which you can run a lot on the same budget as a single manned mission.
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Brokedownclimber
Trad climber
Douglas, WY
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For the time being, we need to keep on developing robotics not only for Mars, but further afield--especially Europa, which is by no stretch of the imagination--inhospitable for human presence. Drilling through maybe 300 meters of ice to get aqueous samples would definitely be "challenging." Europa has a different aura of challenge from Mars, one strictly amenable to a robotic solution.
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limpingcrab
Trad climber
the middle of CA
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I personally think life is unavoidable and common as snot
Why?
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rick sumner
Trad climber
reno, nevada/ wasilla alaska
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Many of the robotic explorations have had spectacular success; the Voyagers, Viking, opportunity, spirit, to name a few. But what is the purpose of these missions if not to pave the way for boots on the ground? Blood, sweat and tears, yes. All human advance worth doing has had its price in human life.
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healyje
Trad climber
Portland, Oregon
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Why?
We're here so the possibility must exist. And in existing that means it's more of a statistical exercise than anything else to guess how much life exists in the universe at any given time. I would guess we're talking 'Goldilocks Zones' for galaxies, within galaxies and down to individual stars. Probably a rare occurrence, but even in saying 'rare' I would think there would be on the order of tens or hundreds of billions of planets with life in the universe at any given time.
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Ed Hartouni
Trad climber
Livermore, CA
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Feb 10, 2016 - 12:20am PT
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Anthropic principal arguments are fraught with bias, but they provide some framework for making estimates...
http://www.supertopo.com/climbing/thread.php?topic_id=2660470&msg=2748443#msg2748443
the paper I linked earlier had this to say as it was concluding:
"The recognition that Earth’s biosphere is in its old age, such that the critical-step model allows a larger number of these events, resolves this problem and suggests that a re-examination of evolution on Earth in light of the model may be worthwhile. According to the analysis described here, the difficult steps that have paced evolution at the longest timescale have occurred at ~1 Ga intervals. This suggests that the penultimate step before the origin of observers (ourselves) on Earth was around the time of the late Proterozoic and may have been the differentiation of the eukaryotic kingdoms of plants, animals, and fungi. To reach that point, several previous difficult steps were passed; so complex life may be a rare phenomenon and observers rarer still. On the other hand, the rapid establishment of life on Earth after its formation may indicate that simple microbial life is relatively common. These conclusions lend some theoretical support to the Rare Earth hypothesis of Ward and Brownlee (2000)."
It is thought that life on Earth was established before the Last Great Bombardment and, at that time, was extinguished, only to come back relatively quickly. As the authors say, microbial life may be common in the universe, and "intelligent" life rarer, but it is a big place, the universe, so even if "rare" there are likely to be many planets with "intelligent" life. Unlikely that they figured out how to find the other rare "intelligent" life.
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Brokedownclimber
Trad climber
Douglas, WY
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Feb 10, 2016 - 08:29am PT
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The carbon/liquid water/goldilocks zone parameters are all there by sheer necessity. Life is by necessity, chemical based, and there are several excellent reasons to include carbon, water, and within a specific temperature range. Let's examine these components in reverse order, with temperature being first. Reactions are required to proceed at measurable rates for them to have any possible significance in a "living system;" this was one of my objections to the Coustenis/Encrenaz book I mentioned in an earlier post, when they went off on some life forms in liquid methane; reaction rates at cryogenic temperatures would proceed so slowly that they become immeasurable on any realistic time scale. On the other hand, temperatures too high generally lead to molecular decomposition of complex systems.
Water: all complex reactions require a matrix in which to proceed, mostly referred to as a solvent. Water is quite unusual in the number of different compounds that it can "solvate," or dissolve. It has a range in which it is liquid; at zero Celsius, water freezes and becomes ice; at 100 degrees Celsius, it becomes water vapor (steam). Other solvents with possible characteristics to dissolve many other compounds include liquid ammonia (too cold), Dimethylformamide (virtually NO natural occurrence known), and a handful of other cryogenic compounds or elements. Water is hence the winner by a large margin. Plentiful (it's basically the substance of comets), great solvent properties, and chemically non-aggressive.
Carbon: Carbon is tetravalent and capable of several forms of Carbon-Carbon bonding: Sigma bonds (single covalent bond), and pi bonds (multiple bonds). Allows for an almost infinite number of complex molecules to hypothetically exist. Carbon, along with Hydrogen, Oxygen, and Nitrogen, compose the great bulk of molecules we have found in living systems. Other elements have been proposed to do things similarly (Silicon) to carbon,but in my professional opinion, highly unlikely; there has been a great deal of effort in laboratories to build Silicon based molecules similar in structure and function to those Carbon based compounds. Generally, this has been a total flop.
So--NASA is looking at all the right things: carbon based/water based/Goldilocks zone.
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limpingcrab
Trad climber
the middle of CA
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Feb 10, 2016 - 08:35am PT
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We're here so the possibility must exist. And in existing that means it's more of a statistical exercise than anything else to guess how much life exists in the universe at any given time. I agree, my point is more that I think we're an extremely improbable anomaly more than evidence that there is life elsewhere worth looking for.
For example, a statistical exercise. There are an estimated 10^80 particles in the universe which can interact an estimated 10^45 times per second with roughly 10^25 seconds since the beginning of the universe. This gives a possibility of 10^150 "chances" for something to happen since the beginning of the universe. It's the Law of Small Probability and the reason statisticians say that anything with a probability smaller than this is impossible.
For the most basic cell you need 60,000 proteins with 100 different configurations. The probability of this happening, even with all the right conditions with all the right ingredients, has been calculated to be 1 in 10^4,478,296.
I would not count on something with that probability happening elsewhere.
the paper I linked earlier had this to say as it was concluding:
Ed, lots of papers talk about when and where life originated, but I would like to know how. This would provide more info about how likely it is to happen again somewhere.
Do the christians have it right, the earth is unique in all the cosmos, humans are the chosen ones and that's that?
DMT, I'm not sure why you keep bringing up religion stuff? We're talking about finding life outside of earth. People take it for granted, I look into the mechanisms and probabilities and so I do not think it is money well spent.
I guess that life is pervasive as well but probably in a lot more forms and chemical systems than we imagine. The carbon/liquid water goldilocks think seems so earth-centric to me. Probably true, it's hard to imagine other chemical systems but they must be there? They would likely follow the same chemical laws, I would think. Maybe not...
There's a reason panspermia is growing in popularity; people are realizing that it's just really unlikely for life to appear as we know it under early earth conditions.
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Brokedownclimber
Trad climber
Douglas, WY
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Feb 10, 2016 - 08:46am PT
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I was always taught that life forms were always improbable, but since they are antientropic, they are in a constant battle with statistical probabilities.
I buy into the panspermia concept; this is one of the better problems to address with robotic space probes, by sampling several comets to bring back large samples for Earthbound experimentation. Since comets are primarily "dirty snowballs," we don't even need to dissolve sample in the laboratory.
Added in edit: comets all originate out in the Kuiper belt, the leftovers from solar system formation. We look at comets, find evidence of life in some form (past or present), and we then know where we came from.
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limpingcrab
Trad climber
the middle of CA
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Feb 10, 2016 - 09:07am PT
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Looking for evidence of the panspermia theory seems like a logical reason to do a little more space digging.
Though life forming elsewhere and then getting here only seems to add another improbable step to the process. If we find evidence then we still have to figure out how it started elsewhere. That sounds like a pain in the butt! :)
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High Fructose Corn Spirit
Gym climber
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Feb 10, 2016 - 09:22am PT
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"For the most basic cell you need 60,000 proteins with 100 different configurations. The probability of this happening, even with all the right conditions with all the right ingredients, has been calculated to be 1 in 10^4,478,296." -LimpingChristian
(Assuming probability calculation is even correct) notice this isn't taking into account cumulative effects of ns over evolutionary time. This is the single step, monkey typing at a keyboard to produce Hamlet nonsense creationists trot out.
Suggests "Climbing Mt Improbable, by Dawkins. He purposely covers this over and over in baby steps for the evolutionarily challenged.
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Ed Hartouni
Trad climber
Livermore, CA
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Feb 10, 2016 - 09:36am PT
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For the most basic cell you need 60,000 proteins with 100 different configurations. The probability of this happening, even with all the right conditions with all the right ingredients, has been calculated to be 1 in 10^4,478,296.
how do you do the calculation? It is not true that the configurations are unconstrained, not all (in fact most) of the configurations are unphysical. But I suspect that the calculation you point to (without reference) ignores that.
As far as calculating the probabilities, you didn't read the paper I linked... which tries to at least bound the issues. In particular, the hypothesis of major evolutionary steps being involved might be an interesting hypothesis, in the one case that it considers (human life on Earth) the probability is low but not impossibly low.
The hard work of understanding the hypothesis and finding tests for it, and separating it from the one test case (which also acts as a bias, but an avoidable one at this stage of our observations) is a work in progress.
As the paper "On detecting biospheres from chemical thermodynamic disequilibrium in planetary atmospheres" points out, "...life typically exploits environmental free energy gradients..." which is probably a key way to think about abiogenesis. Certainly having a solvent like water in abundance provides a place for these gradients to form. Chemosynthesis might be a better starting point and more inline with early Earth environments.
So the questions of life then revolve around how the energy extracting reactions like the classic
12H₂S + 6CO₂ → C₆H₁₂O₆ + 6H₂O + 12S
get to be self sustaining. In particular, the reuse of C₆H₁₂O₆ to power additional reactions.
Self sustaining chemical reactions occur in these free-energy gradient environments without life, but life provides a place for these to occur independent of the "outside" environment... that's an interesting problem.
But without a solution (yet) calculations regarding the improbability of it happening are not possible. You don't know what you are calculating.
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