Alternate endings

A couple of weeks ago I said that the only way the ALH84001 controversy is going to be settled is by the discovery of more meteorites similar to ALH84001. I was looking at the issue pretty narrowly, thinking about ALH84001 itself as the controversy. If you widen out a bit and think about life on Mars as the controversy, there are plenty of ways that issue could be settled.

The first thing to note is that it’s far easier to prove that there was (or is) life on Mars than it is to prove that there wasn’t (or isn’t).

Here are some of the possible missions to Mars that could shed some light on the issue:

• A manned mission to Mars – it seems obvious that having a human on the surface of the planet, analysing the rocks and soil, would get to the bottom of this mystery quicker than any other approach.  The question is who can afford to pay for it?
• A sample return mission to Mars – having a robot return Martian samples to Earth would allow scientists to target specific areas of Mars for study, instead of the arbitrary samples they find in Martian meteorites, and would reduce (but not eliminate) the issues around contamination. There have been sample return missions to the Moon, a comet and an asteroid, but there’s nothing planned for Mars yet.
• More advanced robotic missions to Mars – the next chance for this is the Mars Science Laboratory mission, launching in late 2011. It’s not really designed to look for life directly, but it will look at things like the chemistry and minerals on the surface to see if they could support life.

If any of these found evidence for life, it would immediately give strength to the ALH84001 claim for life (because the paradigm about Martian life would have changed), or perhaps make the whole dispute irrelevant.