Mars Life Confusion

[CraigS]

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

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

Ok .. then this article about a recent study by the University of Florida/Space Life Sciences Lab at NASA's Kennedy Space Centre turns up today: Microbe risk when rover wheels hit martian dirt (http://www.physorg.com/news/2011-09-microbe-rover-wheels-martian-dirt.html) which basically argues that any microbes carried aboard Mars rovers, are unlikely to survive more than a few hours in the Mars' environment. I have read elsewhere that there are at least 13 separate factors on Mars that can kill Earth microbes (not counting Mars' perchlorate salts).

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

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

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

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

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

Cheers

[CraigS]

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

This article (http://www.astrobio.net/exclusive/3144/scarce-shelter-on-mars) says they tested one called 'Psychrobacter cryohalolentis', which thrives under extremely dry conditions and at temperatures as low as minus 10 degrees C. However, it didn't fare too well under the UV radiation to which it would be exposed on Mars. It normally lives in salt brine mixtures .. like what they've recently hypothesised might exist on Mars where trace liquid water might also survive for brief spells. (We had a thread about this just recently here (http://www.iceinspace.com.au/forum/showthread.php?t=79025&highlight=mars+water)).

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

Then there's the good old 'Bacillus subtilis' (http://www.astrobio.net/exclusive/3866/mutant-microbes-test-radiation-resistance) which survived on NASA's Long Duration Exposure Facility spacecraft for six years. It lived exposed to UV radiation of up to 3 times that of its original ancestors (it got its resistance courtesy of a DNA mutation). They sent some dormant spores of this up to the International Space station for 18 months, exposed it to hard UV and cosmic ray radiation. They came back in March of this year (not sure of the results yet, though).

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

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

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

Very intriguing .. to say the least !

Cheers

[CraigS]

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

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

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

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

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

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

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

.. Now that would be a big conclusion !

Cheers

[xelasnave]

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

[CraigS]

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

[CraigS]

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



Cheers

[CraigS]

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



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

Cheers

[Shiraz]

Hi Craig. Interesting thread

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

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

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

Regards Ray

[CraigS]

Hi Ray;

Thanks for your comments - much appreciated.

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

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

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

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

Cheers

[xelasnave]

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

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

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

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

But that guy must be such an embarrasment to NASA.

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

Craig a great review on the situation:thumbsup:.

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

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

alex:):):)

[CraigS]

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

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

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

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

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

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

I will personally find it very difficult to accept:

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

as nothing more than nonsense answers.

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

Cheers

[CraigS]

Again from the NASA astrobiological website …

[mswhin63]

Hi Craig,

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

[CraigS]

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

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

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

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

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

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

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

Cheers

[renormalised]

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

[CraigS]

Take a look at this brief Youtube (http://www.youtube.com/watch?v=qrxvbRA2xCI) on the selected landing site, Gale Crater, for the Mars Science Laboratory/Curiosity rover.

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

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

Cheers

[renormalised]

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

[renormalised]

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




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

[CraigS]

Yep I agree … however reference source is here (http://www.astrobio.net/exclusive/4168/out-of-thin-martian-air-) and it says '1000' ... (blame Michael Schirber). :)

Cheers

[CraigS]

Quote from Wiki .. Atacama Desert (http://en.wikipedia.org/wiki/Atacama_desert#Aridity)


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

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

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

Cheers

[renormalised]

They want to goto Gale Crater because it was most likely the bottom of a large lake. It's a good place to start when looking for the presence, past or present, of life. But that doesn't mean it's going to be found there. Nor does it mean that not finding it there that Mars never had life. As I said previously, the only surefire way they'll know if there was life there or not, is to go there and do the exploring ourselves. We're far better at finding fossils and/or living organisms than computers and machinery/detectors are, and if we get fooled sometimes with what we find, imagine how much more difficult it is for a probe. It can't think, nor extrapolate the possibilities....we can.

[renormalised]

Well, it's a good example and one that NASA uses frequently to model Mars on. As I said, you may not find any life in the desert, but that's not to say the next valley over isn't full of mountain lions and vicunas:)

[renormalised]

If it was 1000 bar, as Schirber says, the ancient martian atmosphere at "sea level" would've been as dense as water. You could just about swim in it!!!!.

[CraigS]

Can you name one place on a planet where we know life emerged, where life cannot be found ?

What then, is the scientific basis for your above statement ?

Cheers

[renormalised]

Yep....the core of our planet:):)

Unless, of course, you subscribe to the Hollow Earth Theory:):P:P

Saying that a planet has never had life, based on evidence from only one or two spots which may or may not have been conducive to having life there in the first place isn't very scientific at all. You haven't exhausted all the possibilities for both the number of sites and degrees of habitation, for a start. And, you're basing your deliberations and prognosis on a statistically insignificant number of sampling sites. However, if they covered a good deal of the surface of the planet and also undertook a reasonable number of borehole surveys and never found any evidence for life on the planet, then I would be inclined to say that Mars never had any life on it. It also goes without saying that this would be in addition to other surveys done of the hydrological and other geological processes which may either support life or possibly mimic it (e.g. inorganic methane production etc).

That's why I take most of these surveys by probes, whilst interesting and rewarding in a limited, specific scientific sense, with a grain of salt. They're not definitive and never will be. Relying on their finding as somehow being able to provide definitive answers to any question is not the way to go about conducting a survey for something as complicated as looking for life. You can only use what they find as possible indicators, but of a rather limited nature. Nothing more or less.

[CraigS]

.. Well, I did say, "Can you name one place on a planet" … as distinct from "in a planet" :):)
Clearly, the proportion of of life bearing locations on the surface of this planet, completely swamps any locations where life may be absent and this then sets the criterion for sampling the surface of Mars.


How much is 'a good deal', and what would be ‘a statistically significant number’ of samples ... and what is the scientific basis for estimating this?
How much of the surface of a life bearing planet supports life, and what does this tell us about how much of the surface has to be searched ?


I think I can see that you'll never be satisfied with any negative finding returned by a robotic probe. What would be your stance if it returns a ‘positive’ result and what is the scientific basis for this ?

We can only work with the tools/technologies we currently have, and are able to send there. The framing of the mission goal is important here, because it is, for all intents and purposes, the definition of the ‘experiment’. The results and conclusions of that experiment should be expressed in terms of whatever they set out to accomplish ... as defined in the wording of those goals.
(Sounds like another post, to me .. see my next one).

Anyway, we should review this aspect once the thing gets there and starts producing results .. we have no idea of what will happen .. it may not even make it to the Crater, anyway.
:)
Cheers

[CraigS]

It seems the title I chose for this thread might be appropriate, as there is clearly a lot of confusion about the MSL/Curiosity mission goals.

So, straight from the horse's mouth (http://msl-scicorner.jpl.nasa.gov/ScienceGoals/) (NASA/JPL's site) …



So, notice that they are searching for present-day evidence of past habitability environments … so, I stand corrected .. and I retract what I implied earlier .. ie: something along the lines of: 'this is the first time they've gone specifically searching for life' … clearly this is not strictly accurate.

My previous statement is as much a result of the media spin on the true mission objectives, (ie: it was not intentionally, my own view).

Cheers

[CraigS]

More detail (for the record) …



I can't believe that they're not sending up a microscope capable of looking for micro-organisms or their fossil remnants ! (See text in bold above).

Cheers

[renormalised]

Well, let's not get into semantics here:):P

You can't use the Earth as a sampling criteria for another planet simply because of the differences which which each planet exhibits. That's why trying to extrapolate from one given example is dangerous, scientifically, and statistically meaningless. You get skewed and inaccurate answers. Or you get the wrong impression about what's going to occur....i.e. your theories are predicated on a set of assumptions which may or may not even be applicable in the circumstances. Nature doesn't follow the scientific method, nor does it have to follow any set of assumptions made by anyone, nor does it have to follow anyone's expectations. That's what makes this kind of exploration interesting. Don't discount anything, just because it doesn't meet your previous assumptions and expectations.



That's about as inane as saying "how long is a piece of string"...it can be as long as you like, or not. It all depends on your definition of what a reasonable amount of coverage is going to be, based on the limitations of your study, but it would most certainly be more than one sampling location. That would tell you very little, either way. However, if you had, let say, 10 or so locations spread widely over the surface of the planet and you were getting results from all of them, either way, then you could make some conclusions from that. But the more you sample, the better your results and the stronger your conclusion can be. If you were getting ambiguous results no matter what you did, then you would have to reevaluate your previous assumptions and your theories and try another tack.



Robotic probes are a "suck it and see" proposition. They limited by their capacity to do only that which they're programmed to do and they can't take advantage of the unexpected or "leap over logic" to look in new and different ways. They can only do what they're designed to do and if the designers get it wrong to begin with or their assumptions about what to find are biased in any way, then the results returned will reflect this. The Viking probes were a prime example of this. They got the results they did because they didn't understand Mars and their assumptions as to what would be there and how they were going to go about testing them were faulty. They produced ambiguous results....yes/no/maybe. Even if the present mission produced positive results, I would still want hands on confirmation and study of a much wider set of samples before I was ready to make a conclusive statement either way. If I was to find irrefutable evidence for fossilised life on the planet, then the case would be closed. If I found nothing after running many tests and sampled a good proportion of the planet, then it would be the same deal. If that sampling meant hundreds of rock samples and many drill cores from a dozen sites or more, then so be it. That's what it will take.



The present set of tools is inadequate for the task. All they can do is give us a few extra bits of information with which to prove up our previous assumptions a little bit better than what they are at present. They will not give us a definitive answer. You may have a friend overseas that you correspond regularly with over the internet via webcam. You may get to know them reasonably well but you'll never know what they're really like until you actually go over and meet them in person. That's when you get your definitive answer. It's the same here.



Not in one piece, at least:):)

[renormalised]

Here's a clanger....what if the life on Mars was silicon based. There's nothing stopping it from being as such and silicon is far more abundant an element in the Solar System than carbon is. How do you test for silicon based life??? They might drive right over the top of a whole patch of silicon based organisms and not even recognise them as even being alive by our definition.

That's the whole problem here....these probes are limited in so many ways. It's the reason why people need to go there and do the groundwork. Despite the paradigms under which they work, people aren't restricted by them unless they want to be.

[renormalised]

With most of them, you need an electron microscope of one sort or another to do this and they're a little too large and power hungry to be sticking on a probe...even one as large as Curiosity:)

You can't rely on the assumption that the Martian microbes exhibited the characteristics of some of their Earthly counterparts and produced macroscopic structures...like microbe mats and stromatolite like structures. Any confirmation of this will come through the exploration of the rocks of the planet as a whole, not from one locality only.

It only goes to prove my case in point.

[CraigS]

Actually Carl, standing back and looking at this thread from a distance, I think I was on exactly the right track from the OP … there is a lot of confusion about how, and what to look for on Mars. I'm not even convinced that sending humans there for a reasonable amount of time, might provide definitive answers to the fundamental questions.

I think your approach (as usual) seems to be to take a bigger step beyond the 'what's known' .. and ultimately in the hunt for exo-life (as-we-don't-know-it), this may be a more effective and efficient way to get the real answers.

Unfortunately, the real world just doesn't work that way and we're saddled with exploration budget and scientific process constraints. Just getting another probe to Mars is probably a huge step forward for NASA at the moment, anyway. (I'm also not attempting, in any way, to criticise your views here .. and I know you're passionate about changing this in fairly radical ways (let's also try to not go down this discussion path on this particular thread .. I understand where you're coming from on this..)).

But working within those constraints, it seems to me that what this mission is doing, is providing more data which ultimately will build a more evidence-based description of life-supporting Habitable Zones (HZ). If they find the remnants of bio-signs, (as defined from an earth-based extremophile model), in the crater .. it would be a huge bonus and would demonstrate that we were well and truly on the right track in our thinking about exo-life .. and where to look for it .. and what to look for.

But in the case of not finding any bio-signs, because all our best effort scientific knowledge has led us to the highest probability HZ we presently know of, and maybe yields a negative result, also says something definitive about HZs and our present expectations about life elsewhere. Exactly what it says, depends on the data findings .. we'll just have to wait and see.

If you think a negative finding says little/nothing, then here's another question: "Why aren't we actively looking for life on the moon ?" Clearly, no scientist takes this possibility more seriously than the Mars case … and no-one is seriously looking on the Moon. So the findings of moon exploration have led us to view the moon is 'dead' and science moves forward on this basis. The presence of humans on the moon made no difference to the conclusion, either. So why would this not happen in the case of Mars after several probes have checked out the scene ?

I don't understand what you mean by 'Silicon based life'. The NASA Astrobiologists themselves, have said that they can only look for what we'd recognise. If we are incapable of recognising something as a life form, then it might as well not exist as far as we're concerned .. its like saying that pink-unicorns exist, and rule the universe .. 'there's no evidence for them but we know they exist' … sorry .. this just doesn't carry any weight in science. This is a faith-based if the pink unicorns don't expose themselves or influence us in a recognisable way. If they serendipitously give off C12 in methane gas ... then that's different, and I might celebrate the findings with the believers, and consider them as candidates for 'reality'.

Cheers

[CraigS]

Ok .. a summary of some info comparing Carbon ( C) vs Silicon (Si) biochemistry follows (from Wiki (http://en.wikipedia.org/wiki/Silicon_based_life#Silicon_biochemi stry)):

- Si has the same valency as C (ie: four), so it is theoretically large enough to carry biological information
- Si lacks the ability to form chemical bonds with diverse atoms .. (req'd for metabolism), when compared with carbon;
- has difficulty forming double, triple or covalent bonds, thus it lacks the diverse compound morphologies formed by Carbon (important for biochemistry);
- compounds of H and Si are highly reactive with water and long chains of these decompose;
- silicones (polymers of Si and O) are more stable than hydrocarbons in suphuric acid environments (quite common);
- complex long chain silicones are less stable than their C counterparts;
- silicon dioxide is a non-soluble solid at temps where water is liquid;
- Si based life breathing Oxygen would produce a solid by-product, thus respiratory organs would be filled with sand. This can be overcome at very high temperature or pressure environments .. (ie: not Mars surface);
- as at 1998, in the interstellar medium, 84 molecules are based on C, whilst only 8 are based on Si. Of those eight compounds, four also include C;
- the cosmic abundance of C to Si is about 10:1, (complex carbon compounds are thus more abundant to support C based foundation for life on planetary surfaces, than Si compounds);
- however, the abundance of Si to C on Earth is about 925:1 and yet, terrestrial life is C based. Thus it seems that C is more successful at forming life, in spite of its less comparative abundance, than Si;
- compounds formed by Si block the flow of heat, nonetheless biogenic silica is used by some life on Earth. Thus lifeforms comprising combinations of C and Si could achieve metabolism and digestion;

So, in terms of maximising the chance of detecting life on Mars' surface, from the above physical facts perspective, it would seem to make sense to constrain the probe/laboratory design around detecting Carbon based organic life … over the Si based life alternative.

Cheers

[renormalised]

Yes....all true. However, silicon based lifeforms would fall under the category of "life as we don't know it". That's what I said originally...how would we test for it. Especially if our life paradigm is looking for carbon based life, or lifeforms that metabolise, etc, in a similar fashion to carbon based forms.

What if the silicon based lifeforms were all solid state and crystalline in nature, which would most likely be the case. How are we going to test for that?? Would you even recognise it as being alive??. You could walk right past it and not even notice. Given our present technology and scientific paradigm in this respect, detecting such lifeforms would be very difficult. For one, we're not looking for them, and we also don't have the equipment to distinguish a silicon crystalline lifeform from a lump of rock.
They may or may not exist, granted, but we'll never know unless we go looking for them...or meet up with one at some stage. We're biased because we are carbon based and it's much easier to detect. But that doesn't mean we should ultimately limit ourselves to carbon based life. To do so would be wholly unimaginative and scientifically narrow minded. Even if we never find any, at least we'd have explored the possibilities.

Just had a funny thought....imagine having a deep conversation with what appeared to be a large lump of rock crystal:):):P

Wait a minute, there's some people who already do this!!!!!:):P

[CraigS]

Down the bottom of that Wiki page, are several references to a major paper, (book actually), authored by the "Committee on the Limits of Organic Life in Planetary Systems, Committee on the Origins and Evolution of Life, National Research Council" its called: "The Limits of Organic Life in Planetary Systems; The National Academies Press, 2007".

All of the questions you have so far posed, Carl are covered in some way, shape, or form in this publication. Its purpose was primarily to provide guidance for NASA on the search for exo-life. The table of contents is here. (http://www.nap.edu/openbook.php?record_id=11919&page=R13)

Of particular interest is the Chapter on "Strategies to Mitigate Anthropocentricity" (http://www.nap.edu/openbook.php?record_id=11919&page=9#p2001293c9970009001).

Here's a quote from that Chapter:



After a hundred pages or so, and eight Chapters, the final conclusions/recommendations are here. (http://www.nap.edu/openbook.php?record_id=11919&page=84#p2001293c9970084001)

It seems to me that the MSL/Curiosity Rover technologies are a direct flow-on from these recommendations.

There has been a lot of consideration of all the aspects you raise .. and then more.
The conclusions have given rise to the technologies being sent along with MSL/Curiosity.

There's very few questions left in my mind that the Mars probe is maximising the chance of detecting recognisable bio-signs, in the most probable Habitable Zone presently accessible, and known to humans.

The definitional scope of this 'experiment' is sufficiently tight to enable very specific conclusions, within the practical constraints of the mission. The instruments themselves are designed to return precise results to minimise measurement uncertainties and rule out inaccurate readings.

What the conclusions of the measurements will be, depends on the data, and the conditions under which it is gathered.

One possible outcome could quite easily be, in the case of "no-organic chemistry bio-signs detected" in this high probability HZ, that there are indeed, "no-organic chemistry bio-signs detected" in this high probability HZ, of a high probability HZ planet.

If this were to happen, I would suggest a big re-think of HZ definitions in terms of environment, biologies, search strategies, missions, and detection technologies, would be a very rational outcome.

The opposite findings, I would think, would probably be sufficient to justify a manned mission at some stage in the future.

Cheers

[renormalised]

Look what the paper is resting upon, Craig...organic life. In other words, carbon based or analogues of carbon based life. Even their mineral based "information carriers" are still within the confines of an organic chemistry of some sort. Darwinian evolution, etc. I've seen this paper before. They haven't covered anything to do with possible inorganic lifeforms, at least none that I can remember in the report.

What about lifeforms that are completely devoid of anything to do with organic chemistry. A solid state, crystalline lifeform would fit that description. If you saw a crystal sticking out of the ground and all you could see was some play of light through the crystal, could you tell if it was a living organism or not??. Given everything that was written in that report and the raison detre of the Curiosity mission??. I'd dare say no.

What about something that appears as an interstellar dust cloud. Have a read of Frank Boyle's "The Dark Cloud".

What about a lifeform that is nothing more than a type of living energy?? How do you begin to categorise that?? How do you recognise it??

In any case, talking about life and what it is.....what is life, actually. What allows a complicated soup of molecules to spark and become life. It's not self similarity and complexity or the ability to reproduce. There are a vast number of organic chemistries which fit that description that are as far from being alive as a glass of water. Ultimately, all any living creature is just a bag of organic molecules and water. So what sparks life....no scientist has the answer to that one. So, to preclude the possibility of another form of life other than organic (no matter its chemistry) and any process that drives it, is premature. We just don't know. The only thing we can do is work with what we got and find that first. Other possibilities will come if we look for them at a later date. If they don't, then we move on.

[CraigS]

Carl;
I don't mean this to be insulting, but I find your thinking to be unconstrained to the point of being science fiction.

How could anyone possibly conceive of a way of detecting, either remotely or locally, such inorganic lifeforms ? Especially if we haven't even detected them here on lifeform central ? Would we even call them lifeforms at all ? If so, why ? If not, then their very definition automatically excludes them from the scope of detecting lifeforms !

How would you design the detection systems for MSL/Curiosity with these models in mind ?

We've gotta get real about this .. otherwise the money will disappear from the budget before we can spend it !! ;)

Cheers

[renormalised]

Einstein once said the most important part of doing science is having an imagination. He's right....it's precisely where Relativity and many other great leaps forward came from. Where do you think String Theory originally came from. It's where most of our greatest inventions also came from. Edison said that invention was 10% inspiration and 90% perspiration....Tesla said he quoted that because he was the most unimaginative person he'd ever met:):). Leaps forward can come from anywhere. Even from the "everyday drudgery" of doing science...where someone takes a step back from the assembly line process of hypothesis testing and looks at a problem from a new and different angle. Not that this way of doing things doesn't create progress. It just happens far more slowly.

Being able to locate and detect such lifeforms is upto someone to come up with a way of doing so. We know about inorganic chemistry, we know about the structure of crystals, optics, EMR, etc etc. What we need to do is to put together what we already know and extrapolate on the known principles. Experiment with what we have and come up with new ideas.

This place is hardly lifeform central:). Even though we don't know of any other life bearing planet, this universe is a very big place. We should and must be prepared for any eventuality, whatever way it happens to go. Even then, we'll be in for some very big surprises.

I agree, we need to concentrate on what we know to try and find out if that type of life (carbon based) exists elsewhere in our Solar System. But even if we don't find it (which I think we will, eventually), that doesn't mean to say that we're going to be the norm throughout the galaxy or the universe, even. We may just be the unlucky sods to be one of the few (or many, who knows) that only has one life bearing planet in a system. We may even be surrounded by silicon based life...we just don't know. Look at it this way...we've barely been doing science for not much longer than 400 years and rigorous science for 250 years (if you count the Industrial Revolution as being a part of it). We're still in the first day of kindergarten...we haven't even reached Grade 1 yet:). We have a long way to go and very much to learn...even of the basics.

To even think we know what we're doing or have some sort of handle on things is arrogance in the extreme. People who actually know very little are usually the ones who think they know the most. It's a very bad habit that a lot of scientists have gotten themselves into. It's a bad habit this human species as whole has gotten itself into.

Oh, you speak of lifeforms that we haven't even detected yet on Earth that are like anything I have mentioned.

Ever heard of viruses. Prions??. They are carbon based, for the most part, but they most certainly don't act in a way you'd call life in any obvious sense. Many scientists don't even consider them as being living organisms.

What do we really understand of them...less than you might think.

[CraigS]

No .. but if we don't face up to the evidence of a negative finding in a high probability HZ, we would never revise the search criteria, (the primary one being, the definition of HZ .. as well as the astronomical/geological/chemical theoretical grounds underpinning it). No progress will be made !

I call this denialism !

… If this were to happen, we'd be deceiving ourselves (scientifically) ... for who knows how long !?!


This fear of feeling 'unlucky' is an irrational barrier to progression as a species. I see it as being more important for humans to overcome this, than the discovery of hypothetical exo-life forms. It could be argued that this fear is the basis for 'conjuring up' in their 'existence', in the first place!

Frankly, I presently don't care whether they 'exist', or not !


Your commentary on this thread reminds me of the question:

"How long is the coastline of England ?" …

The answer is of course, "Infinite" … why ? .. because it is a fractal pattern ...

Cheers

[supernova1965]

Apathy is the biggest killer of scientific progress when people don't care one way or the other. If they didn't care there would be no debate so I don't believe it when lack of care is stated.

[renormalised]

Who said we were a high probability HZ zone?? Just because we're here...one example?? It's nothing more than your opinion. No one knows the answer to this one, simply because it's an argument from just the one example. Neither you or any other person has any idea what the conditions are like around any other planetary system. We don't know what the probabilities for life in around those other stars might be. We can only speculate and take rather loosely defined parameters to work off. For all we know, we might be a rather poorly solar system so far as life is concerned. Then again we might be positively bursting. A negative finding based on the only example we've got means very little, except in the context of our own Solar System. Nothing more or less.

If anything by thinking that we'll find the answers by just studying the one example is an even more cogent case for denial and deception than realising that whatever we do find in this Solar System is only a very preliminary result. One that will only give us a very rough set of definitions from which to work with.



My quote had nothing to do with fear of being unlucky or anything like it. It was a statement of probabilities and their possibilities. No need to get all philosophical and "self help" about this one, Craig.

If anything, staying within any particular paradigm because it's what you feel comfortable with accepting is more stifling of progress than anything else.




Then why bother with all this debate???. It's not going to make the science any more "real" by debating it. Nor is it going to prove the argument, either way.



Is it, now. Think again.

[CraigS]

Warren;
I unfortunately, have to say this, because you continually mis-read, misinterpret and emotionalise where I'm coming from. Your misinterpretation then calls into question my integrity:

I find you have so many interpretive filters running simultaneously, I question how you could ever see the perspective science offers.

We are in a Science Forum !

Let me explain by demonstrating that your above interpretation is completely off track with where I'm coming from:


If 'they' can't make themselves known to us, for any reason whatsoever, then there is zero objective, independently verifiable evidence supporting their existence. Because of this, there is also no internally self-consistent theory supporting their existence. 'Their' 'existence', is thus entirely speculative.

I choose to personally 'not care' about speculation, by not adopting this as reality. There are far more productive ways for me to spend my time on this Earth. If you find this to be a problem, then that is a problem of your making, in your own mind … and absent, by freedom of choice, in mine.

I truly wish you could drop these faith-based filters, so as to at least understand that my integrity in terms of completeness and wholeness, when it comes to this matter is complete and consistent when measured against what I stand for. If I'm presented with evidence to the contrary, then I'll happily alter my stance.

(I'm also not particularly interested ego-centric interpretations of the term 'integrity' being used as a weapon of intimidation by others, either).

Cheers

[renormalised]

Bit of a case of the pot calling the kettle black here, Craig.

Accusing a person of coming from an emotional and egocentric basis for their arguments when you're doing exactly the same, yourself.

Take a step back and really have a good look at what you're writing. You're only fooling yourself by denying it.



That's just one example.

This "holier than thou" attitude towards what you believe science to be is starting to wear a bit thin, Craig. It's also starting to become rather sanctimonious in its scope. Whilst the scientific method is rigorous and objective in its approach (or at least we hope it is in its application), science itself has never been, nor will ever be, the black and white creation that you think it to be. Not whilst people, many of whom have rather large egos to salve, reputations and careers to protect are involved. Science never has and never will be conducted in a vacuum, especially where human proclivities are concerned. We are not robots, nor are we computers. You want a completely logical, rational and objective answer to everything...ask a computer. Don't expect a person to reply in the same.

[xelasnave]

Craig said......
"without an over-riding theory whose goal is to refine the search field options .." ..I agree such is a given I would have thought.

Thanks for taking the time for outlining your views and the facts covered.

It is interesting the passion that surfaces in this forum and although some of the "debates" take on a familar form I personally find them most interesting. The fact fall out is most useful.

The engagements are thought provocing and that cant be a bad thing.

alex:):)

[renormalised]

Yes, Alex, that is a given....it's a guideline for doing the search. But what if you find something outside the paradigm. Are you just going to ignore it, or are you going to alter your paradigm to include the new information. Guidelines are what they are, they're not hard and fast rules that must be followed implicitly. Same with a theory. You follow it for as long as that theory or guideline remains applicable to the situation you find yourself in.

[xelasnave]

Yes of course Carl but I took it that Craig was suggesting I had not considered the necessity of a plan.

I am with you in your specific comments here but moreover, if I can generalize, with your sensible approach and recognition that we may in many fileds find things different to what we currently expect.
I admire the feet on the ground but consider the possibilities approach.

I have been thinking about the meaning of life..not in the spiritual sence but what is the purpose of life... as an initial thought it would seem that life releases energy back into the Universe and assists entropy:shrug: ... but I wonder if life is some what universal why should it be so?

Anyways most interesting posting by all:thumbsup:. I love reading the posts in this forum.
alex:):):)

[CraigS]

G'Day Alex;

I really wish I could get back to 'the facts' !
Most of the last few posts have been ad-hom attacks, and are most definitely off topic .. and .. 'yes', I can say that because I was the OP.

None-the-less, there many more interesting facts to record.

Such as the MSL/Curiosity Landing Site Selection Criteria … (http://msl-scicorner.jpl.nasa.gov/landingsiteselection/)

Clearly, NASA perceives this site as affording the best opportunity of successfully obtaining evidence suggestive of a past or present habitable environment.
Interestingly also, from Wiki … (http://en.wikipedia.org/wiki/Mars_Science_Laboratory#Selection)

.. from which they subsequently selected Gale Crater. I'd suggest that between 33 and 50 sites might cover a wide distribution of the surface of the planet, too (I might do some checking on this, also).

… All designed to optimise the primary mission goal, which is …


Cheers

[xelasnave]

mmmm only investigating the surface ... maybe there is a advanced civilization living far under ground forced there by climate change.
:lol::lol::lol:

I have read a little over the years on site selections interesting stuff...its great having goggle Mars which helps get a view on where they consider.



alex:):):)

[renormalised]

Now there's a great idea for the future....Google Mars....want to find where under your dome you live, or where Uncle Bill climbed down the cliff face at Olympus Mons, goto www.google-mars.ms (http://www.googlemars.ms) :):P

[supernova1965]

http://www.google.com/mars/:rofl:

[renormalised]

That's the Earth version:):P

Mine's the "local" version:):P

[xelasnave]

It is such a pity that Percy Lowell never saw such a map.
mmm I am suspicious there are no canals.
alex

[renormalised]

There aren't....some were related to certain surface features but most were nothing more than optical illusions.

[xelasnave]

It is embarrassing to have to point out I was joking Carl:lol::lol::lol:.

However that poor man was convinced. I think he (or someone on the basis of his early observations of Mars) suggested the canals were transport system for an advanced race.

alex:):):)

[xelasnave]

AND he was not a lite weight if you take the time to read up on the man.
alex:):):)

[renormalised]

No he wasn't, very true. He was quite established and famous.

And, I know you were joking:)

[CraigS]

Ha ! … Coincidentally, in today's news …. (here's a laugh )…

Methane debate splits Mars community (http://www.physorg.com/news/2011-09-methane-debate-mars.html)




As I have said throughout this thread and elsewhere, real science will only happen if minds are receptive to objective and independently verifiable measurements, (within the bounds of precision/uncertainty), and an internally self-consistent, theory. Even if the results are negative.

If this approach isn't followed … and the results are ignored, then it is not science … and 'faith-based belief', will continue to run riot.

Cheers

[renormalised]

I'm not debating you about that, I agree. Where I disagree is in the rigidity of your interpretation and the exclusion of other possibilities, which may even be found within the bounds of carbon chemistry, where life is concerned. You cannot discount anything until you have the evidence to do so. Nor can you count on anything, for the same reason. If you confine yourself within the paradigm just for the sake of being anal about it, you will, or could possibly, run the risk of losing out on finding something you least expect.

However, any results we find for life solely restricted to the one example we have of it and it's extrapolation to the solar system can only act as a very loose pointer to what to expect outside of it, in the wider universe. They are nothing more than very loose approximates for guidelines. Why do you think there' such a big debate about methane and life on Mars at present. It's because they know that their paradigm could be flawed and they don't want to say anything until they get the results back from the probe. But even then, they'l be arguing about it until the cows come home. How are they going to test to see if it's biogenic or geological...test for the ratio of C12 to C13???. Works here, to a greater or lesser degree, but what if Martian life doesn't work that way. Ever consider that?? What if martian microbes give off similar isotopic ratios as geological processes for methane back here on Earth...how are they going to figure that one out?? A probe isn't going to be able to tell the difference. That methane could be coming from a bunch of microbes a couple of hundred feet down below or from a hot granite pluton baking in water rich sediments or other wet wallrocks a mile or more down. Probes are nothing more than 'suck it and see" propositions. They're limited by both the scope of their instruments and their programming. Yes, they can be modified on the go, now, but they're still hampered by the fact that they can only do what they were made to do. If you want to do any real work on anything, you have to do it yourself. That's why any really definitive answer to the question of other life in this solar system, especially for Mars, is only going to be answered when manned flights are undertaken. Unless, of course, the probe to Europa drops its subs into the conjectured subsurface ocean there and something swims in front of the camera!!!! Or eats the probe!!!!:):P