Study: Martian Soil Has Signs of Life

geoffrobinson writes "Reuters is reporting that a scientist from Germany believes Viking probe data shows signs of life. From the article: "Joop Houtkooper of the University of Giessen, Germany, said on Friday the spacecraft may in fact have found signs of a weird life form based on hydrogen peroxide on the subfreezing, arid Martian surface. His analysis of one of the experiments carried out by the Viking spacecraft suggests that 0.1 percent of the Martian soil could be of biological origin.""

Comments

I worked on the Viking Lander project...

[mbone]

I worked on the Viking Lander project (but not on the biology side). Before the landing, NASA published and sent around little promo phamplets describing what a positive (biological) response would be from each of the 3 biological experiments. (Along the lines of, add nutrients to a soil sample, get CO2 out, sterilize the next soil sample, add nutrients, get no CO2, that is evidence for life. No CO2, or CO2 with a sterlized sample, not evidence for life.) I still have mine in my basement.

Each of the two landers had 3 biological experiements. All six worked fine. All six had a positive response based on the criteria published before landing.

However, because the mass spectrometer detected no organic molecules (not one of the pre-published tests), these results were ascribed to non-biological causes.

I could never understand why one of the biological researchers didn't just say, "we have detected life, by our published criteria, but we don't understand it." However, none did.

Science doesn't always move in the nice linear fashion described in the text books...

The Same Only Different

[DynaSoar]

Subject applies to both the analysis and the conclusion.

Analysis at the time for one test showed negative, the other was inconclusive (not "yes").
At that point (as Sagan announced) they were cautiously hopeful, since the tests looked at different things, and some forms of life could appear negative to one and not the other. The negative test was replicated in Antarctica and showed negative there too, making that Mars analysis also inconclusive. No idea what Sagan had to say about it then.

It's unlikely life as we know it could be "based on" H2O2. It'd be far more likely to be based on water and highly tolerant of H2O2. The peroxide would come from ultraviolet from the sun hitting exposed water. I expect pretty much any exposed water (even ice, though the reaction would be slow) would have a fairly high percentage. But the water wouldn't be pure and so the peroxide would break down, keeping it at a low equilibrium. Life as we don't know it might use H2O2 for energy catalyzing it to break it down, pulling in more selectively from the environment or creating its own via an ultraviolet driven photosynthesis-like process.

To exist in H2O2 living things have to be able to break it down, such as we do using superoxide dismutase. If we didn't, the peroxide would eat (among other things) the walls off our cells because it destroys the lipids that the walls are made of. Germs don't have this mechanism, and that's why peroxide is a good antiseptic. However, with nothing like lipids or their precursors to work with, any Martian life is not likely to have lipid shells. That makes it unlikely the have any similarity to Earth life. Even the (theoretically) first living things on Earth, cyanobacteria, have lipid-based shells.

So, the news here is that someone's projecting a specific form Martian life might take based on the Viking data. The implication is that if correct, the Panspermia hypothesis probably doesn't hold. On the other hand, there can be a highly complex collection of compounds collecting ultraviolet, making and/or using H2O2, and developing more of itself via an endothremic self-organization process. Life as we don't know it might not be confined to a small, protected, self-contained module, but might be spread over large areas. It stretches the definition of life, but it's about time we do so, so we know it when we find it because "The thing about aliens is, they're alien".