Bitch Ph.D. is temporarily away, but loyal spouse Mr. B. has taken control and turned the site into — a science blog! Today he’s talking about the interesting issue of contaminating other planets with organisms from Earth.
Nowadays, when we send out space probes, we sterilize them. What little I know of this seems to indicate that our sterilization processes may be far from perfect. Regardless, the rationale for sterilization is sound — whether or not life exists or has existed at the probe’s destination, sending some of Earth’s life to the destination would potentially muck things up beyond repair. When we fear a spacecraft might not be sterile, we purposefully destroy it while it still has fuel enough to perform a fatal maneuver, as we did with the Galileo probe to protect the potential life on Jupiter’s moon Europa from earthy microbes possibly riding on the probe. These are real concerns that govern our use of current robotic space probes.
Suppose we didn’t worry about such things. Suppose there is life, an ecosystem, where we send a space probe. Suppose further, that some hardy bacteria or fungus stowed away on the space probe and is thereby introduced into the alien ecosystem. Chances are it will die out. However, there’s a slim chance that such stowaways could find habitat, potentially altering or even destroying an existing alien ecosystem.
I suspect it’s pretty unlikely that we will ever find anything worth of the name “life” on Mars or elsewhere in the Solar System, but I’m certainly no expert. If we did find anything, of course, it would be incredibly important, so I am happy to keep an open mind. (On the other hand, given the small chances, I agree with a colleague who says “It’s more important to look for supersymmetry than for life on Mars.”)
Still, one of the absolutely fascinating recent advances in the study of life’s origin has been the possible role of extraterrestrial chemistry. The classic Miller-Urey experiment demonstrated the possibility of creating amino acids by shooting sparks into a chamber designed to mimic the atmosphere of the young Earth. But apparently there’s good reason to believe that the Earth’s atmosphere wasn’t really like that in the experiment; in particular, it had more oxygen and less reducing compounds, and nobody has been able to make amino acids by zapping an atmosphere of that type.
On the other hand, conditions for synthesis of amino acids may exist in space! Interstellar clouds appear to be good places to create prebiotic organic compounds, or even proto-cells. It’s perfectly plausible that these could have been brought to Earth early on by crashing comets and meteorites. If so, it’s clear that the other planets would have received similar interplanetary donations of organic materials; no reason to believe that they necessarily evolved into life, but a fascinating possibility nevertheless.
I heard that a U.S. moon probe was intentionally not sterilized before sending it. Then, when the astronauts landed, they collected a sample that still had bacteria from over a year before. I don’t have any documentation, but the source is a professional astronomer.
Rule number one of science policy: you’re not going to get funding by putting down other fields.
If it is more important to test supersymmetry than search for life on Mars, than neither will be done…
Prioritizing within fields is good and proper, and helps get funding; trying to claim cross-field priority is counterproductive.
That depends on whether or not there is a relatively fixed amount of ‘science funding money’ to go around, surely?
True, I agree that it’s important not to denigrate other fields, and didn’t mean to do that. I was presuming that everyone can see the obvious interest in finding life on Mars, and using that to demonstrate the importance of looking for supersymmetry.
I’ll never be a politician. Surprising they even let me have a blog.
Seems to me that even for the purpose of finding life on Mars, a manned mission is the least efficient way to go. It is really science vs. advertizing, not one kind of science vs. another.
Tim, I suspect you mean the Surveyor 3 pieces recovered by Apollo 12 after 31 months. Streptococcus mitis was recovered, perhaps from the probe and not afterwards contamination, and 1 sample out of 33 lived in culture. ( http://www.lpi.usra.edu/expmoon/Apollo12/A12_Experiments_III.html , http://science.nasa.gov/newhome/headlines/ast01sep98_1.htm ). I believe Surveyor missions were done before sterilization was an interest (in some cases).
Moshe, the discussion probes or manned missions is old and boring. A generalisation of Steinns argument on space missions is valid here. And there is positive reinforcement between both types in the public interest so doing both is probably best ROE if one can afford it.
One naturally cannot afford both, otherwise the discussion would really be boring, but I agree it is a little stale…
Two quick points;
Astrobiologists at JPL have been doing lots of work demonstrating that bacterial spores in particular can survive the transition from earth’s surface to orbit and back. I haven’t looked at the S. mitis study cited above. It’s not the bug I would have expected, but that is neither here nor there. As far as life on Mars or other planets in the Solar System, all of us are completely unqualified to say (and I definitely mean no insult there!), although it is great fun to speculate. I’ll say this; there are essentially no environments on or in this planet (outside the mantle) that do not contain living microorganisms-from the driest desert to the deepest oceanic trench to miles below the earth’s surface (deep crust bacteria are very interesting, and a significant challenge). I’d be very skeptical of any logical argument that leads to the conclusion that there is no life outside Earth. That said, finding it might be very tricky. That’s probably more than two quick points…
“One naturally cannot afford both”
How is that natural, and is not both planned (but not funded) today?
Missions could also be much cheaper with cooperation and without status projects as ISS, so I would prefer cutting that pork instead of strangling investments towards perhaps lower ROI or certainly public interest.
Regarding the early Earth atmosphere and the Miller-Urey experiment there was an interesting perspective in Science a few months ago:
“Rethinking Earth’s Early Atmosphere”, Christopher F. Chyba, 962-963 , 13 May 2005.
It seems there may have been more hydrogen in the early atmosphere than believed which would make synthesis of amino acids easier.