Posts Tagged‘gullies’

Dry Ice on Mars (and Earth).

Mars doesn’t have much of an atmosphere and the little it does have is rather hostile to life, being composed almost entirely of carbon dioxide with only small percentages of other gasses detectable. Due to the freezing temperatures that grip it constantly -60°C in summer and -125°C in winter a lot of this carbon dioxide ends up in its solid form, usually buried in the permafrost. Last year NASA even confirmed that Mars experiences dry snow a phenomena where frozen carbon dioxide falls to the surface in the form of snow not unlike the water based version we have on Earth. These are all mightily cool in their own regard but there was one particular interaction that came to my attention recently that’s just so much cooler because I realized I had first seen it for myself in my backyard.

I had heard about these gullies before and had always wondered how the heck they formed. It’s not like Mars is a completely dead planet, we’ve caught crazy things like avalanches happening on it, but things that look like they require surface water (or some other liquid) in order to create them are usually out of the question (at least for new features anyway). They’re even reminiscent of the sailing stones in Death Valley, although we’ve probably solved that mystery, but the lack of something at the end of them was the thing that was really puzzling.

Where I saw this in my backyard was a chance encounter with a couple blocks of dry ice that came with a delivery of frozen meals. They weren’t as big as the blocks in the movie above, although you can get them pretty easily if you know where to look, but of course the science nerd in my wife and I couldn’t resist playing with them in the kid pool we had set up. The result wasn’t exactly surprising since we’ve all seen this kind of stuff before but it was rather interesting to see the same principles at work on Earth just as they are on Mars.

The effect isn’t nearly as dramatic but you can definitely see the same carbon dioxide cushion at work which makes the block appear to glide on the surface rather than bobbing in it like water ice does. Another cool thing (which I didn’t show in the video) is when it’s placed just below the surface that same cushion will actually propel it straight to the bottom where it will pin itself and bubble like crazy until it’s all melted away.

I’d recommend doing this for yourself as it’s one thing to see it in a video and a completely different thing altogether to play around with it. Of course there’s a whole host of other things you can do, some which I’d probably not recommend (anything that involves a pressure vessel contains a certain amount of danger), but just watching it interact with other things is pretty satisfying.