More promising news about the “potential” for life on Mars comes in by the day - evidence of ancient lakes, flowing salt water, etc. Do whatever probes we have up there have the capability of concluding yay or nay, however? Do they have microscopes that can look at a soil sample and conclusively identify a living, moving microbe?
Frankly, the odds are overwhelming that there isn’t, and never was, life on Mars. Why? Well, for one thing, the Fermi paradox implies life has to be pretty rare. For another, water and warmth probably isn’t enough. You need just the right chemistry.
An interesting opinion, but hardly a factual answer to the question.
Sure. If the camera happens to pan across something green and tentacled waving cheerfully, I imagine that would do the trick. Or slightly less implausibly, if it spotted a tiny splotch of what looks like mold and were to see it growing over time and in response to moisture and sunlight.
But few people expect anything like this, more or less on the grounds that on Earth where life exists at all it tends to be exuberantly abundant. So we tend to think if life isn’t obvious, it’s probably not there at all, and so far life on Mars has been quite nonobvious. This reasoning isn’t entirely illogical, since successful life pretty much by definition fills every conceivable local niche and has to have a superabundance in general to survive the occasional catastrophe over geological time spans.
What you probably want to know, however, is this: if there is some tiny, tiny amount of purely microscopic life – say some very thinly scattered colonies of bacteria – could this be found by the present instruments? The answer is, not easily. They don’t carry microscopes capable of resolving bacteria, for the simple reason that searching through soil cubic micron by cubic micron is no way to find things in a reasonable amount of time. If you searched through the sands of the Sahara cubic micron by cubic micron, you’d probably run out of time and energy before you found your first bacterium. You need to know where to look before you deploy the microscope with its teeny tiny field of view.
That’s what these probes are actually for: figuring out if there’s any place where it’s profitable to look much more closely. The idea is to find out where it is most likely to find anything living – where there’s liquid water, for example – and then consider whether to send something that could look very specifically for life in those identified places. So their instruments are geared to finding the conditions for life, not life itself. They have cameras that can resolve enough about rocks and soil to let mineralogists characterize the local soil conditions. They have detectors that ponder the composition of the Martian atmosphere, the amount of sunlight, et cetera. They have spectrometers that can identify the chemical make-up of rocks and soil.
The Viking landers did attempt to find life per se (because it was possible at that time it lay thickly on the ground, or just under it). They did this by incubating soil samples in what was thought would be some kind of growth medium and looking spectroscopically for the typical signatures of metabolism. The results were ambiguous, in that some of the signatures of metabolism appeared, but the pattern suggests some funky inorganic reactions and not life as we know it. (This is one reason to thoroughly characterize Martian soil chemistry first – so that you can clearly distinguish it from any of the chemical processes that denote life.)
The search is verrrrrry slow because each time you learn something, the only way to apply it going forward is to design another $150 million one-way robot and send it off for an 18-month trip. Although it’s usually argued that robotic planetary exploration is cheaper than human, it may turn out the search for life doesn’t fit that handy conventional wisdom. It could be having a geologist and microbiologist in spacesuits on the surface of Mars, with a variety of basic scientific instruments – spectrometers, hammers, shovels, test tubes, chemistry set, microscopes, et cetera – would settle up the question faster and cheaper than sending special-purpose robots every two years for a century or so. Humans have an ability to interpret ambiguous data and adapt exploration immediately that can’t be matched by any computer program.
The Curiosity Rovers includes a sample analysis instrument package to analyze the chemical composition of samples. The presence and ratios of various isotopes and the signature of some organic compounds could in theory provide definitive evidence of the presence of life.
But until we see something moving there, it is only theoretical.
And then we have to be sure it’s not a microbe transplanted from Earth.
The on-board sensor instrumentation on on the Mars Science Laboratory (‘Curiosity’) is as follows: mast-mounted high definition multi-spectra cameras (MASTCAM), manipulator-mounted ultra high definition (0.014mm resolution) camera (MAHLI), X-ray diffraction system, pulsed neutron emitter (DAN), tunable laser spectrometer, alpha particle X-ray spectrometer, laser-induced breakdown spectroscope (ChemCam), gas chromatograph, quadrupole mass spectrometer, multiple sensors for navigation and self-diagnostics
There is not a high resolution microscope suitable for imaging microorganisms, nor a means to prepare samples for suitable imaging. However, the MASTCAM, tunable laser and x-ray spectrometers, ChemCam, an the GC/MS systems are all suitable to look for signs of both chemical life itself and the waste products and detritus we would expect it to produce. These are frankly a more precise and practical way of looking for life than just sifting through random samples of dirt. However, even if we find indications of life (which we thus far have not, save for some spurious and very transient emissions of methane gas) we would still need to assess whether it is indigenous or whether it came from Earth, either via ejection from meteorite impact and resulting transfer, or carried by Curiosity itself. Extensive measures were taken to sterilize the rover and spacecraft that carried it, but it is nearly impossible to eliminate all possible reservoirs of microorganisms robust enough to survive the planetary journey. (By the way, this argues against sending a human crew to look for signs of microscopic life; as large organisms, we host an almost uncountable number of microorganisms–some of which we’re still discovering–and it is a practical impossibility to sterilize our spacecraft and exterior of suits from carrying organisms we host within and upon our bodies.)
The potential for life on Mars, either in the past or currently, cannot be precisely stated (hence, why we are looking for signs) but the existence of liquid water at least allows for conditions under which chemical life could potentially form. Since we have only directly observed Earth-bound life, we can make only rough hypotheses about the conditions in which life could exist, and we’re being constantly surprised by the existence of life in what are presumably harsh conditions on our planet. The likelihood of extant life on Mars, however, seems remote, simply on the basis that while life on Earth spreads rapidly and converts the environment to one more supportive of it self, leaving very clear chemical traces that are distinct from any natural non-living processes, we see almost nothing that looks like it could be the result of life processes on Mars. The lack of nitrates or other complex compounds in the accessible soil level, the high ultraviolet radiation (which would break down organic molecules rapidly), and stability of the atmosphere without either oxygenated or reducing components gives no indication of recent or current life processes. If life as we know it did once exist on Mars, it likely was not complex and went extinct long ago. We should not, of course, dismiss the possibility of self-organizing thermodynamically regulating systems which do not look like life as we know it (e.g. not a carbon-nitrogenous backbone of nucleic acids which catalyze and define the construction of proteins and lipids) but we would still expect waste products and molecular structures that look like something not borne of natural processes.
The possibility of life elsewhere can be divided into two distinct trunks of probability: either life on Earth is the result of some special, nearly unique set of conditions not to be found anywhere else in the observable universe, and thus, our life is unique, or it is the result of some natural processes and combination of conditions that occur as some measurable frequency. In the latter case, even if the frequency that these conditions come together is relatively small on local timescales, the sheer vastness of space and billions of years of duration over which conditions could occur argues that life of some kind should be very, very common. And the prolificacy of life on Earth would seem to indicate that once it gets a toehold, so to speak, in an environment, it multiplies and evolves rapidly, both to fill every possible energy-providing niche, and ultimately to modify the environment for greater suitability. The aggregate survival of life on Earth in the face of many known, and likely other unknown catastrophic events argues that once life exists it continues and even thrives in the face of radical modifications of environment and severe challenges, which again tends to indicate that life does not exist on Mars, and if it did, it didn’t get very far along in sophistication and diversification.
In the past we’ve assumed–largely from the child-like arrogance of our special uniqueness–that the former case is true, and that we are somehow specially endowed with life by some kind of creator who desires our worship. The more we see of the universe, however, the more we realize that we don’t occupy some privileged stage or unique condition, and that no indication that we are in any way special or gifted or powered by some esoteric energy field, and that everything about us, including our cognitive abilities to look around at the Universe and rationalize about our supposed entitlement is most likely the result of normal matter obeying a fairly small set of mechanics and producing the majestic of creation simply by dint of complexity and stochastic behavior. There is no reason these same principles shouldn’t give rise to life elsewhere with statistical frequency given any conditions under which stable macromolecules (or other hypothetical stable discrete systems could form).
Even if there isn’t life on Mars, there may be life elsewhere in the solar system–on the Jovian or Saturnian moons, or perhaps even in the frigid but surprising active Pluto–and with almost certainty somewhere else in the galaxy that we are just not equipped to observe with current technology. Whether there is intelligent life capable of cognitive abilities comparable to our own is another question, and one about which the Drake equation really gives no insight, but we can observe how cognitive intelligence has been a successful evolutionary strategy for a small but evolutionarily distinct number of species on our planet and make the observation that we don’t seem to be unique in that way, either, other than happening to be the first to develop sophisticated tools and industry, allowing us to do amazing things like kill each other en masse and be obsessed with achieving a kill screen on an obsolete video game. Go humanity.
Stranger
I think any “top-heavy” object would be proof. Something shaped like a toadstool, which could occur by either growing that way, or being displaced into that configuration, by at least an ambulatory organism, if not an intelligently controlled one.
It wouldn’t be proof in and of itself, but would certainly be a center of attention, warranting detailed scrutiny to rule out life.
Macroscopic life certainly isn’t expected on Mars, and there are plenty of natural formations on Earth that are ‘top-heavy’ (search on “mushroom rocks”). Organisms at this size would definitely leave traces of waste and detritus which would be observable by the same methods as looking for microbal-scale life, and in fact, we would expect an ecosystem of organisms on microscopic scale to accompany any more complex life.
Stranger
There are certainly top heavy things on earth cause by water erosion (and probably wind erosion) that have little to do with life. Neither of those operate too well on Mars with very little water and not powerful winds (the winds fast but not powerful – a major error in “The Martian” I believe – one of the few.)
The Viking landers included tests for adenosine triphosphate (which came up negative). That’s a chemical that’s found in all living cells on Earth, and which would be extraordinarily unlikely to exist without life… but we have no particular reason to expect that life unrelated to us would use that particular chemical. It’d probably use some chemical or another to do the same job, but it probably wouldn’t be the exact same one. Plus, of course, all the Viking experiments could show was that there was no ATP in the specific samples they tested-- There might be some deeper underground, or in other locations.
And in fact, if there is extant life on Mars, it is likey buried deep under the surface layer where water may remain in a liquified or gelled state and ultraviolet radiation cannot penetrate to break down organic compounds. This argues for doing more global survey and surface sampling missions at geographically disparete sites to find most favorable conditions before making concerted effort to look directly for signs of living organisms. Mars Global Surveyor and the ESA Mars Express missions were a start to this. The collaborative ExoMars program would have been a great follon on, but the current administration defunded the Mars Exploration Joint Initiative to pay for overruns on James Webb and the Space Transportation System. NASA still plans to send the as-yet unnamed Mars 2020 rover and the InSight lander, but with Mars Scout Program cancelled after MAVEN there are no solid follow-on efforts planned. The long discussed Mars Sample Return Mission is currently unfunded even for proposals, and the lack of support for joint programs (largely for political reasons but also because of the funding focus on SLS and a hypothesized but defined crewed mission) means there is no sample return mission on the foreseeable mission horizon.
Stranger
It’s my understanding that the Fermi paradox relates to the apparent absence of extraterrestrial civilizations. The paradox doesn’t really apply to microbial life or even complex but non-intelligent life.
It does.
Sending a human does not solve the problems of Mars exploration. It does not increase the amount of renewable energy available from solar power to transverse Mars, and instead adds another system that requires power and cannot be turned off. It does not increase the number of instruments available to detect microscopic life, and instead requires many tonnes of life support. It makes the probe significantly more complex and less reliable, while also being much more punishing of failure. It makes it harder to avoid contamination with Earth life that might produce false positives. And so on.
If you want humans to interpret data from Mars, send the data to the humans, don’t send the humans to the data.
Wait, am I understanding that right? They won’t even entertain proposals for a sample return mission, but they will entertain proposals for a manned mission? Wouldn’t any manned program necessarily include a sample return mission as a partial proof of concept? I mean, surely you want to prove that you can get payloads back into space before landing your first humans, and if you’re doing that, why not make the test payload something worthwhile?
NASA isn’t currently funding proposals for new roboic Mars missions (at least, as of FY2014). Anyone is, of course, free to put together a proposal and the supporting studies and analyses on their own; that, and three bucks will get you a cappucciono at the Coffee Bean. I’ve never seen so much as an acknowledgement from the couple of adjunct studies I’ve worked on even though the results appear to correspond to, and possibly have fed into evolutions of the Mars Design Reference Missions (DRM). The DRMs provide a ‘snapshot’ of the current parameters around which a crewed Mars mission would be designed and the decisions for architecture. There are numerous ongoing studies on various capabilities required for a crewed mission of which is the most challenging is the entry, descent, and landing (EDL) mode, given that our current capability for landing is limited to about 1000 kg (1 T), and a crewed mission would have a minimum landed mass of around 30 T even with supplies and habitat pre-staged.
The current DRM 5.0, dating from 2009, has five major architectural decision points, but I don’t believe any of the options assume a robotic sample return mission. I would agree that a sample return mission would be a desireable precursor to a crewed mission on a number of aspects, but it carries with it considerable cost (~US$5B) and schedule impact. Making the next most opportune mission in 2033 would likely precluded waiting on the execution of a sample return mission as the earliest it could launch at this point would be mid-2022 with a return date in early 2025, giving only eight years to make use of the data for mission planning and equipment design. Of course the “Mars Soonest!” crowd would argue that we don’t need any precursor missions and that we’ll just load up a bunch of random gear and let the crew McGyver their way to mission success, a philosophy that makes sense only to people who believe that “The A-Team” is a documentary about modern mercenary operations. The reality that ensuring a high probability of success (versus throwing a couple hundred of billion dollars into a crap shoot) really means developing an infrastructure that can be demonstrated to have good reliability and the ability to deal with contingencies.
It makes more sense from a dollars per unit data metric to continue funding robotic missions for the foreseeable future while advancing the state of the art in propulsion, energy, and habitation technology, as well as in-situ resource utilization methods in order to be able to supply and support crewed interplanetary missions using mostly space-based resources (at least propellant and bulk consumables such as water and air). In fact, there is little practical need to land people on Mars at all; the limitations of current rovers isn’t that they’re robots, but that they are limited in available power to that which can be supplied from the small solar arrays or RTGs on-board the rovers. A crewed mission would require substantially more power for the crew support alone, notwisthstanding that necessary for excavation, surface transportation, et cetera. A more sensible use of a crew is in providing local control of surface rovers and probes without the infuriating time delay caused by the distance between other planets and Earth-based mission control. We may have other objects for landing crew–prestiege in being the first to put footprints, or establishing a permanent crewed outpost, or whatever–but from a science standpoint, putting (gloved) hands and (helmeted) eyes directly on the surface is not justifiec by either cost or capability. Nor will it be practical in many cases (Venus, Io, Europa) for the foreseeable future.
Stranger
The Fermi paradox is talking about INTELLIGENT life and extra-terrestrial civilizations, not merely life. Intelligent life seems to be very rare (perhaps unique to the Earth), but this doesn’t say anything at all about simple life as would have perhaps happened on Mars. Even if you want to posit that intelligent life DID happen on Mars, the Fermi paradox wouldn’t really come into play, since they would have died out billions of years ago.
No, but if you take the Fermi paradox 1 more step and apply modern knowledge to it, you realize that either (1) modern knowledge is wrong. We cannot make ourselves thousands or millions of times smarter, or build an intelligent machine, and using the increased intelligence, advance technology to the limits of physics within a few decades. (2) Intelligent life is vanishingly rare. Like, no other instances of it within our galaxy at the least. (3) interstellar travel, even at half a percent the speed of light is impossible
#1 and #3, we have strong, nearly overwhelming empirical evidence that they are incorrect.
If intelligent life is insanely rare, it does follow that the precursor - life at all - must also be pretty rare.
No, it doesn’t. As far as we know, in the over half a billion years life has been on this mud ball, exactly one species has become intelligent enough to send and receive potential radio signals…which is what they are basing a failure of the FP on. There are basic assumptions even in that, i.e. that other intelligent species and inter-galactic civilizations would be using radio just like we did and do, which might or might not be valid.
No, but as Stranger points out (I’m agreeing with him for once!), life tends to expand to fill every niche. Intelligent life has the capability, if certain assumptions are right, to expand to fill every niche across an entire galaxy. Those assumptions are that (1) you can build a solution to boost intelligence thousands of times above natural levels, letting you quickly and easily engineer solutions optimized to the limits of physics and (2) interstellar travel at a non negligible rate, like 0.5% C, is possible.
If life had expanded to cover this galaxy, we should already be able to see the results of this.