17 November 2008

An Ancient Ocean on Mars?

Posted by Ryan Anderson


Bad Astronomy has a post today about possible evidence for an ancient ocean on Mars, based on this press release. It’s an interesting post, but all the hype confused me. The results that supposedly suggest an ocean on Mars are old, it’s just the interpretation that is new, and that is not very convincing to me. The basis of the argument is that potassium, thorium and iron were transported to the northern lowlands, leeched out of the rocks and re-deposited in a thin layer. The detections of these elements tend to be below the “shorelines” that people have drawn on Mars, and therefore this is claimed as support for an ocean.

My questions is: why not just put the volcanic rocks in the lowlands to begin with and skip the whole business with the transport, leaching and re-deposition? It’s certainly possible that the elements were deposited by oceanwater, but I don’t think it’s necessarily the best explanation.

Don’t get me wrong, I love the idea of an ocean on Mars. But that’s why I’m so cautious about people claiming to discover one. There are so many scientists (and others) who want Mars to once have been Earth-like, that they start to see evidence for it everywhere, even if it isn’t really there, or isn’t very compelling. The more you want to find something, the more cautious you need to be when claiming that you have found it.

I know, I know. The headline: “Oceans on Mars are One of Many Possible Explanations for Observations” doesn’t have quite the same ring to it. But I think it’s important to save the big headlines for the big discoveries. These results and their interpretation are fascinating! But I’m not convinced yet.