Update on the Mars dust event
Posted by Emily Lakdawalla
09-04-2009 16:18 CDT
It's been a week since I posted a storm warning from Mars, and I have an update with the latest data. In brief: the southern dust event is not abating, but the dust has not spilled across the equator; everything's staying in the south for now.
To quickly review, I'm talking about data hot from Mars Reconnaissance Orbiter's Mars Climate Sounder, an instrument that stares off of Mars' limb to take profiles of atmospheric properties like temperature, pressure, and dust abundance. (It's not as easy as that of course; what they measure directly is the brightness of the atmosphere at several near- and mid-infrared wavelengths, and they have to do mathematical modeling to extract the information they're really looking for.) In the diagrams below, we're basically seeing the temperature of the atmosphere high above the ground, from about 20 to 40 kilometers elevation.
Two weeks ago, Mars looked typical for the season, with a very cold spot at the north pole, and otherwise fairly uniform temperatures that don't change a whole lot from day to night.One week ago, the story was quite different: the south was heating dramatically every day and cooling off at night, the likely result of dust getting lofted high into Mars' atmosphere. There are hot spots in the north, too, probably a result of changing atmospheric circulation patterns that are making air descend in the north. Now, a week later, the whole south is almost uniformly hot; check out how much the south pole has warmed, indicating the dust has spread all the way there. It definitely qualifies as a planet-encircling event. Still, the warming (and, presumably, the dust) is sticking to a region that appears to be south of both rovers, which is good news, especially for Spirit. What's odd about the April 7 data is that the warming in the southern hemisphere, previously only a daytime phenomenon, is now happening at night too. What could be causing that? I asked David Kass, and he told me that they don't yet understand what has suddenly made the nighttime temperatures warmer (this has only happened since the weekend, he said, and it developed quickly). "We have some speculative possibilities. The most likely so far is significant additional dust at very high altitudes. But it's going to take some work and modeling to determine the actual cause and what else might be contributing."
Some things we can explain -- some things we can't. There's always more to learn!
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