The lure of ‘life’ on Mars

With less than two weeks until the NASA Mars Phoenix mission arrives on Mars there’s been a lot of news about how the probe is going to go about looking for life on the red planet. It’s an exciting mission and one I’m really interested in, but we have to be careful when talking about exactly what it is actually going to do. My worry is that, if people get fixed on the idea we are looking directly for ‘life’ with Phoenix they are going to miss the other important results that will, no doubt, come back from this mission.

Phoenix’s instruments will be examining the north polar regions of Mars, scrutinizing the soil there, hopefully taking the first ever direct sample of Martian ice and investigating the environment of the region. What it will not (at least intentionally*) be doing is carrying out a direct search for life, such as microbes or any other of microscopic living organism. We will almost certainly need a sample return or some extensive in-situ studies to prove that.

However, what Phoenix will be doing is using an advanced spectrometer to look for the fingerprints of important organic molecules in the gas of vaporised martian soil. A special instrument, called the Thermal and Evolved Gas Analyzer (TEGA), will be looking to see if there are any molecules or signatures in the soil samples which might signify past ‘biological processes’.

Those results will be extremely important. Previous probes such as the Viking spacecraft have done similar experiments with ambiguous results. It will be later missions (possibly the giant rover Mars Science Laboratory) that will tackle the direct search for life, potentially with a sample return mission. More importantly Phoenix will be looking at the broad overview of the martian north pole and its history.

By studying the geological history of this region it will be looking at whether the conditions for life were there in the past. That’s first and foremost a big question. If (and of course that is one big if) there was life on Mars in the past that would clearly have big implications on the search for it, on Mars, today. It’s fair to say as well that if life didn’t arise in the past, that would have just as big an implication. So how is it going to do this?

Phoenix is going to study the history of water around this region of Mars. With an advanced weather station and other sensing instruments its going to be examining both the atmosphere and the ground. With the robotic arm it will hopefully gather some of the ice and soil for analysis. These results will tell us a great deal about the habitability of the martain soil. It might be that only a few centimetres below the surface the conditions there permit life to survive against the paucity of water and harsh UV radiation. Most exciting for me is the possibility that there may be what the NASA scientists call ‘short-lived’ liquid water sitting in the cracked icy layers of soil. Although it won’t last long on the surface, if this water is there it might give us a fleeting hint of what lies beneath.

It’s certainly an exciting time for Phoenix, let’s just keep our fingers crossed for 25th May. Keep up with the mission here.

* There is a caveat here that a few missions have, through serendipitous discoveries, been able to make discoveries that they were never intended to make. It’s possible (I suppose) that Phoenix might make just such an interesting discovery.

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