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The Planetary Society Blog
By Emily Lakdawalla
Mars Climate Sounder: Quick Looks at Mars' Weather
Apr. 3, 2007 | 11:22 EDT | 15:22 UTC
I've just posted an update on the status of the Mars Climate Sounder studies of Mars' weather. They are having a bit of trouble with the instrument, with a pesky error showing up in one of the two motors that moves its scan mirror back and forth, but despite these problems they have already acquired more than four million soundings of the atmosphere. To get a handle on this data, they're employing quick-look plots that reveal nifty details in atmospheric features. I explain these plots in more detail in the update, but here's a description of one fun feature. First, the plot:  Quick-look plots of Mars Climate Sounder dataThis graph shows data from four of MCS's nine channels for a four-hour period starting at 12:00 UTC on October 6, 2006. Each channel surveys the Martian atmosphere vertically from about -10 to +80 kilometers above the ground (-6 to +50 miles). For the three infrared channels, A2, A4, and B1, the data is plotted as "brightness temperature," where black and blue represent the lowest brightness temperatures, and yellow and red the highest. For the visible channel A6, the data simply represents relative brightness. The data comprises slightly more than two orbits; the graph below the MCS data shows the latitude at which the measurements were taken. Mars Reconnaissance Orbiter is in a nearly polar orbit, so the spacecraft travels nearly from pole to pole. The plots begin near the north pole, where it was late summer. The most obvious feature common to all four channels is a region of low brightness temperature as Mars Reconnaissance Orbiter flew near the south pole, where it was late winter. Credit: NASA / JPL-Caltech |
One curious feature visible in all the channels are inverted U-shaped loops. These are not Martian flares! They are vertically thin, high-elevation, latitudinally-restricted haze layers. The hazes do not actually form loops in the Martian sky. Their loopy appearance is caused by the forward limb-viewing geometry of the Mars Climate Sounder instrument combined with the curvature of the planet. As the spacecraft moves (from left to right across these graphs), the high haze layer peeks over the horizon. The layer rises in Mars Climate Sounder's field of view as the spacecraft approaches it until the instrument sees it at its true altitude, then the layer appears to fall as the spacecraft passes over it.
Three distinct loops are visible in this plot. The first lies just south of the equator on the night side, so it is visible in channels A2, A4, and B1, but not the visible channel A6. It lies at an altitude of approximately 60 kilometers (36 miles). One full orbit later -- 30 degrees of longitude to the west of the first orbit -- there is a similar layer at a slightly lower elevation, perhaps 55 kilometers (33 miles). Finally, there is another layer on the day side just north of the equator, at about 65 kilometers (39 miles), visible in channels A6 and A4 and barely discernible in B1.
Thanks to Tim Schofield for his patient help with these explanations!
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