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The Viking Landers, 25 Years Later
bavid314 writes: "CNN has a decent story looking back on Viking I and Viking II. For someone who wasn't alive at the time of the landings, it provides a good synopsis. Furthermore, it evokes the question of why recent missions fail to include biological experiments to test for the presence of life."
I've always been proud of the fact that my dad worked on one of the "search for life on Mars" projects -- the GCMS project (gas chromatograph mass spectrometer, affectionately dubbed the "green-colored Martian sniffer").
Those were the days when we did big space science, before we lost some of our hope.
But boy did it make the "what my parents do" presentations more interesting for me.
Dad's retired now, but he taught me how to program (a career I likely wouldn't have if it weren't for the space program) and gave me the foundation for a good geek life.
If a silicon-based one was possible, Earth was the perfect planet for it.
Well, perhaps not. If carbon life is 100,000 times more likely to develop than silocon life (for reasons mentioned elsewhere sucn as silicon's weaker binding properties and lower reactiveness in simple compounds), and earth has 10,000 times more silicon than carbon, then under those conditions carbon based life is still 10 times more likely to develop than silocon based life. This by no means rules out silocon based life at all. Indeed, perhaps the presence of carbon, even in smaller amounts than silicon, was sufficient for carbon based life to evolve first, preventing any silicon life from ever developing (or outcompeting it in the primordial soup, which amounts to much the same thing).
In which case earth would not be the perfect place for silicon based life to develop, as it has been "poisoned" by the presence of carbon. This does not remotely prove, or even strongly imply, that silicon life can't and won't develop elsewhere. It merely suggests that, in earthlike conditions, carbon life is much, much more likely to develop. Even that is uncertain, as we have but one data sample, namely the Earth. The opposite could well be true: maybe silicon life is ten times more likely to develop than carbon based life, but we are one of the "ten percent" which have, nevertheless, developed carbon based life. Without additional datapoints (other worlds) the best we can do is make suppositions about this sort of thing, and any supposition we do make is necessarilly suspect.
The Future of Human Evolution: Autonomy
Well, similarly, I see no reason why Mars wouldn't be teeming with life that's not carbon-based.
Problem is that no-one can come up with any kind of chemistry which can be as complex and varied as carbon based organic molecules. Also these kind of compounds are very common.
A more definite answer to that question (and a nice exercise in interstellar navigation and precision landing) could be obtained by landing a probe right next to one of the Viking probes and
a horribly compex piece of navigation. Also the only time anything like this has been done used a manned lander
seeing if some of the materials they were made of have been chewed at, or consumed, at a rate that's not explainable by natural phenomena.
Only proves anything if this has actually happened. Martion lifeforms might find a terestrial machine inedible, or take a long time to noticably consume such a large object.
That doesn't exclude other forms of silicon-based life, but chances are any life that is out there is carbon-based (though not necessarily the same as carbon-based life as we know it.)
Possibly similar compounds, but different in issues such as chirality. (Some common organic compounds have multiple chirality). Also it's perfectly possible to have amino acids, fatty acids, sugars, nucleic acid base pairs which do not exist in terestrial organisms. Let alone that you can have different "genetic codes" even with DNA/RNA chemically similar to that on Earth.
The fact that it didn't succeed in raising funds is in no way evidence that it was in fact a ploy to raise funds. In fact I have been complaining about NASA's exaggerations for many years now on the grounds that it's short sighted, people will eventually see through them, and thus the money will suddenly dry up due to disillusionment with the whole subject of Mars.
---- SIGFPE
Of course, it's still a massively controversial subject and they must have been hoping that it would be good for their funding. The press release was dated August 1996, which is certainly a good time for NASA to have been feeling a bit poor. In fact, looking at the 2000 NASA budget testimony, if the 1996 release was a bid for funding, it really didn't work very well.
Try getting an organic chemist to say "silicon-based life" with a straight face.
IANAOC, but the short answer is that while you can substitute silicon for carbon on paper, the properties of silicon are different enough to make this impossible in practice. For instance, the silicon equivalent of methane (CH4) is silane (SiH4) which spontaneously burns on contact with oxygen. Silicon-to-silicon bonds are weaker, so making large compounds is difficult; smaller silicon compounds (e.g. SiO2) are often stable and unreactive.
That doesn't exclude other forms of silicon-based life, but chances are any life that is out there is carbon-based (though not necessarily the same as carbon-based life as we know it.)
This is roughly the insight that led to the Gaia hypothesis.
James Lovelock came up with the idea when he was hired to do some life-detectors for Viking. His reasoning went along the lines of:
- 'Life' can be taken to refer to a property of a system that allows it to stay in a non-equilibrium chemical state. (bear with me)
- 'life' achieves this by interaction with its environment.
- This interaction therefore leaves the environment in a non-equilibrium chemical state - for instance the Earth's atmosphere wouldn't contain 20% oxygen in the presence of lots of reducing agents unless something is actively producing fresh oxygen.
- therefore a nice test for life on, e.g., Mars is to look at the chemical composition of the atmosphere and see if it's chemically stable in isolation. Which, disappointingly perhaps, it is.
The nice bit about this approach, I thought, is that it uses a sufficiently generic definition of life that it avoids the carbon-centric issue. As long as you go along with his 'life' definition.The really hairy conceptual leap from there is the full-on Gaia hypothesis which roughly says that if 'life' is defined as above, then the whole Earth might be treatable as 'life' since it's out of chemical equilibrium. Take it or leave it - Lovelock refuses to refer to Gaia as other than a Hypothesis.
Good piece or Gordian-knot cutting by Lovelock, I thought.
TomV
It's interesting how they regard the Viking probes as something gigantic and powerful(and, importantly, successful) as opposed to recent probes that are smaller and cheaper. But I don't think that smaller and cheaper is worse... it obviously reduces the impact in case of a failure. Moreover, I would reason that the instruments used in modern probes are lighter, cheaper, sturdier, smaller, more powerful versions of the ones used on the big old probes. And they made significant advances in a ton of other areas, they know more about where to look for failures, they have more powerful computers, transcievers (DSN I guess) and so on... so why is the faster/cheaper/smaller approach showing itself as a failure?
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The Vikings were great spacecraft, there's no doubt about that, and the things that they discovered about Mars have been invaluble to planetary scientists over the past 25 years. However, the biology experiments on board the landers were just poorly thought out crap.
Prior to the Viking lander touchdowns, the only spacecraft to touch down on mars was the Soviet Mars 3 mission which landed safely in 1971, only to have its computer lock up 30 seconds later such that no data was ever sent from the surface (D'oh!). All that was known about the surface was that which could be learned from orbiting spacecraft -- geomorphology, aeronomy, and the like, but certainly no chemistry. By sending generic rudimentary biology experiments to Mars without any knowledge of the chemical environment they would be operating in NASA set itself up for the rash of uninterpretable data that those experiments returned. In addition, the biology experiments for Mars were designed by astronomers, not biologists, and their focus reflects this.
This failure has an important lesson to teach us about planetary exploration: don't get ahead of yourself. Before we can go searching for life, we need to do some basic science, learning about how a planet works before blindly looking for our version of life everywhere. Despite this, every NASA Mars press release mentions how Mars Odyssey, or MGS, or whatever new spacecraft will be looking for life, and that's too bad. At least the spacecraft themselves are better thought out, sent to address specific scientific problems and to teach us more about the planet Mars so that someday we CAN go look for life, but this time, we'll do it RIGHT.
If you stack all papers discussing life on Mars on top of eachother, you can probably reach Mars
Non-oxygen-breathing does not equate with non-carbon-based.
Please wait until you've finished your 10th grade biology class before making this proposal.
Well, similarly, I see no reason why Mars wouldn't be teeming with life that's not carbon-based. A more definite answer to that question (and a nice exercise in interstellar navigation and precision landing) could be obtained by landing a probe right next to one of the Viking probes and seeing if some of the materials they were made of have been chewed at, or consumed, at a rate that's not explainable by natural phenomena.
"A door is what a dog is perpetually on the wrong side of" - Ogden Nash
I'll tell you why they stopped searching for life, they already found it. Or rather, it found us.
For the last couple of years the martians have been sending their best specimens to earth to infiltrate into our governments. Just recently they booked an enormous success. They managed to get one of their top spies into the most powerful position on earth. Sure, he still has a speech impediment and he still has trouble with human logic but it worked! The humans actually bought it!
No no.. its just that there was more national pressure back then. It was seen as real important. Thus more money, more brilliant people.. that sort of thing.
Hard to believe that it's already been 25 years since Leif Erickson and his Viking pals first came to North America.
Of course, they landed way up in what is now the Canadian great white north, so it is not too surprising that no signs of life were found.
Look at all the Mars stuff happening - Mars in the Media, and the immediately recent Mars opposition and new hubble shots, the killer success of the surveyor mission, the probes heading there right now, the rover mission and others.
NASA should be pimping the hell out of it. The existence of extraterrestrial life, even microbes, is a question of enormous magnitude. It is truly a question of biblical proportions. NASA's work on Mars could perhaps unravel one of the greatest mystery humans face. It will be very interesting to discover what is returned to Earth in the Mars soil samples returning to Earth in 2005. You can check out the strategy paper NASA issued on researching Mars exobiology.
The ultimate mystery!
Isn't the best evidence that there is intelligent life out there the fact that it hasn't contacted us? :)
http://www.themeparks.ie
The US government is afraid of finding out that life on Mars is more intelligent than life on Earth.
Phoenix
I am me. Insightful, isn't it?