Is There Really Life on Mars?
If you want to start an argument among a group of space scientists, one of the easiest ways is to ask whether the evidence suggests that there is life on Mars. I know, because I've asked that question, off and on, since the Viking landers reached Mars in July of 1976.
The question became interesting again last week, when Michael Mumma and others at NASA published a paper in Science. In the paper, they described their observations of methane in Mars' atmosphere. The formal announcement at the NASA website for Mars exploration is titled "Martian Methane Reveals Red Planet is not a Dead Planet." It was reported in the press as if life had definitely been found. Look closely at the announcement, though, and you find it really says that the results show either that there is life on Mars or Mars is geologically active.
Methane, composed of four hydrogen atoms attached to one carbon, CH4, is the simplest possible hydrocarbon; when we use it at home, it's called "natural gas." As millions of teenagers have demonstrated, it's the flammable component of the gases produced by digestion.
These new results are certainly suggestive and interesting. To understand them, we ought to think about the conditions on Mars a bit.
At one time, it was almost commonplace belief that there was at least some life on Mars, based on its similarity to Earth and on seasonal changes that could be observed through telescopes. But as our observations got better, that all changed.
Mars had less atmosphere, and was a lot less similar to Earth, than we had thought. In fact, the pressure on Mars is quite a bit less than the pressure in a vacuum-packed can of coffee. There is no open water, there are no canals.
There is ultraviolet radiation that would kill Earthly life in minutes and no water on the surface at all. In fact, the soil on the surface of Mars is saturated with oxidizers. It's as if you soaked the surface with hydrogen peroxide from the drug store.
Opinion quickly changed, and the results from the Viking landers made it seem even less likely there was life, although there have always been a few planetary scientists who dissented.