Please keep in mind that Curiosity has not the capability to recognize biological molecules, only organic ones. That means that even if it finds current life, it will only be able to recognize the presence of organic compounds. That is why the "organic, not biological"; it may well be biological, but Curiosity cannot know.
Sigh. There is no difference between "organic" and "biological" molecules chemically. There is no "vitalism" force which makes a biological molecule special.
Also, Curiosity is quite capable of unambiguously detecting life on Mars, the question is just a matter of how likely it would be. Curiosity can detect a wide array of organic compounds, and if a sufficient quantity of the right variety of compounds were detected it could be near incontrovertible proof of life. For example, if you fed a pile of fine wood shavings into Curiosity's SAM instrument you would be able to look at the data and go "yup, this is absolutely, definitely, wood, it couldn't be anything else".
The difficulty is that realistically the amount of organic matter from some life form that is sampled by Curiosity could be fairly small and very difficult for the rover to get any useful data out of. That's why Curiosity was not designed as a "life detection mission", which would require other instruments. However, that doesn't mean Curiosity is incapable of detecting life, just that it would likely have to get fairly lucky to do so, and most of the evidence it would gather would likely be fairly circumstantial rather than definitive.
This is all rather speculative though as there has been no information provided on Curiosity's new findings, merely more speculation from people who don't know the findings (in this case the manager of JPL).
"Curiosity - ha spiegato Elachi oggi - non è dotato di strumenti per trovare tracce biologiche", ossia molecole necessarie o prodotte da forme di vita, "ma ha la capacità di riconoscere molecole organiche". Già questa sarebbe una novità importante: tali molecole, composti a base di carbonio, non provano di per sé la presenza di vita, ma senza di loro la vita non può svilupparsi.
If Curiosity founds "formic acid", that is a simple 5 atom molecule, then it is not a proof of life, because there are some non-byological process that create that molecule, so it is distributed everywhere in the universe. (I'm not sure that "formic acid" is the best example, but probably any small organic molecule is a good enough example.)
If Curiosity founds "celulose", that is a very complex ~20000 atom molecules, with the atoms arranged in a very special scheme, then it is almost almost almost sure that it was created by some kind of life, because we don't know any non-biological process that can make it.
The main problem is that there is no distinction between organic and biological molecules, so you can't make a sensor that distinguishes them.
The very simple molecules (formic acid) are expected to be found even in places without life. The intermediate molecules (some sugars, aminoacids, even some nucleotides) are more rare, but not unexpected. The big complex molecules are unexpected, so after discarding everything else, the conclusion would be that in that place there is something living.
A similar problem is "How many grains of rice is a lot of rice?": One is not enough, one million is enough, but there is no a clear border. There is not a clear border between organic and biological molecules; the question is "Is the probability that a molecule like this was created by a life form greater than the probability that a molecule like this was created by an inorganic process?"
> The main problem is that there is no distinction between organic and biological molecules, so you can't make a sensor that distinguishes them.
For a given molecule, life tends to strongly prefer either the left-handed or right-handed version.
Curiosity's gas chromatograph can tell them apart. If it finds a strong handedness preference for several chemicals, then Mars almost certainly has life.
I think you may be confusing liquid chromatography and gas chromatography, gas chromatography afaik can't distinguish between the left handed and the right handed form of a molecule but liquid chromatography mass spectrometry can (and that's not the most sensitive / efficient way to do it either).
One of the GC columns has a chiral stationary phase. Chromotography works whether the carrier fluid is a liquid or a gas. The real problem with gas chromotography is that amino acids have a low vapor pressure. They seem to be chemically functionalizing them to improve the volatility.
What they're talking about is the difference between measuring a dead organism (looking at organic molecules, something Curiosity is capable of doing) on the one hand and performing experiments to detect active biological activity of a live organism on the other hand. Look at the experiments that the Viking Landers carried for examples of this: http://en.wikipedia.org/wiki/Viking_biological_experiments
Is this some kind of job security on NASA's part? The unspoken goal of these mars missions has always been to find life, so why not make sure the rover has every possible piece of equipment to do so. Unless they want to send another one. They certainly have good arguments for the pitch now.
If only it were that easy. Curiosity already is a $2.5 billion roving science lab, quite literally. However, it's necessary to have a guiding principle for what you set out to investigate when you decide what equipment to bring to Mars, and in the case of Curiosity that principle has been mineralogy and chemical composition. Overwhelmingly, Curiosity's instruments are designed to be able to determine the mineral makeup of rocks and the chemical makeup of samples. This gives it the possibility of discovering hints of life if it gets lucky, but overall it's not very good at that role.
Partly this is because we still need to know about the mineralogy of Mars, there is a ton we don't know. Improving on that knowledge will mean that we are all that much more able to target the regions of Mars that are more likely to harbor or have harbored life. And then we can send a "life detection" class mission.
However, such missions aren't easy. Consider a few of the challenges. In order to determine the composition of a rock you really don't care about the extreme minority constituents of that rock. If you can figure out what the elemental composition of the rock is within, say, 1% that can be a good day. However, if you want to determine whether or not a sample of dirt contains living or formerly living microbes then you are talking about a teeny, tiny fraction of a fraction of a percent of the material. Which means that you don't just need to break down the material into its major parts, you need to figure out how to focus in your studies to just that small bit of biological material. Which could mean extremely high magnification microscopes, for example, though that has a throughput problem. Or it could mean making use of various experiments to prove the existence of running metabolic activities within living organisms, such as using radiologically tagged nutrients, for example. But these sorts of things are pretty much a crap-shoot, and wouldn't help if the biological samples are no longer living.
Also, a NASA life detection mission requires much higher standards of clean-room assembly and pre-launch sterilization, which add expense and complication to the mission.
This is the sort of question that keeps NASA scientists up at nights. It's a fundamentally tough problem to tackle, especially with just a rover full of instruments and experiments. You can try to design the experiment such that you can show that it's the presence of external samples which show signs of biological activity and not the parts of the machinery itself (e.g. comparing results with and without an external sample present, comparing different samples, etc.) but even that isn't foolproof.
Keep in mind that for unmanned "life detection" missions a spacecraft would not just be constructed in a clean-room but all of its components (as well as the whole vehicle) would be extensively sterilized (at 112 deg. C for about 30 hours, for example). Additionally, the vehicle would be extensively swabbed throughout assembly to search for any amount of biological contamination.
However, more than likely the focus will not be on an unmanned life detection mission but rather on a sample return mission (which would be optimized to try to find samples containing life) or on a manned mission (which would also likely entail sample return). In either case there would be a considerable amount of research resources available to study any samples of Martian life, should it be found, and bring to bear instruments or tests which would unambiguously show it to be of a different origin to Earth life.
Perhaps every possible equipment is not possible given current funding; It could be a trade-off between probability of detecting possible indicators of life (organic compounds) and ability to detect more certain indicators of life (actual examples of life).
Imagine if you were only allowed to purchase $100 of equipment - it could either be a digital camera that can take pictures of fossils and definitively prove life exists on Mars once and for all, which is less likely than, a piece of equipment that detects the presence of methane in the atmosphere. (more likely but less definitive proof).
I think to the lay public, it feels like an excruciating process to announce that there is life on Mars.
The way NASA communicates to the public makes it tough. If a troupe of green martians wearing tophats and kilts started doing the "Lord of the Dance" routine in front of the rover, NASA would announce "We are still awaiting test results, but we believe that the Curiosity rover may have discovered organic materials that resemble felt that resembles something that could potentially be a hat."
This brings to mind an old adage about eggs and baskets.
More seriously, adding extra components to a mission means many more man-hours designing, testing and vetting the extra functionality, and also adds a boatload of extra weight, which makes the entire thing massively more risky and expensive (especially with the rover's at-the-time-unproven landing mechanism). There's no real need to send everything at once, especially if a lot of what you're sending could be ruled out as entirely unnecessary depending on the results of other tests you're carrying out.
So, finding some organic molecules in Mars is totally expected. On the other hand, finding a any proof of life in Mars would be amazing, but as far as I understand this "report" is only an uniformed speculation.
