Click for original image.
Today’s cool Mars image is especially cool because it is of the exact same place on Mars I had featured in a picture only a little more than one month ago. I return to this spot only a month later because the location was yesterday’s featured captioned image from the high resolution camera team of Mars Reconnaissance Orbiter (MRO). The difference is that this time the camera captured a dust devil there that wasn’t there previously. From the caption:
The dust devil is casting a shadow, which can be used to estimate its height. This image is part of ongoing monitoring activities by HiRISE of seasonal activities on Mars.
Over the years, HiRISE has observed many dust devils. Just like on Earth, dust devils develop when the Sun heats up the ground such that it warms the air directly above it. When air heats up its density decreases causing it to rise up while colder air sinks down driving local convection.
If the region is windy, the wind my end up rotating the “convection cells” caused by the vertical motion of air leading to development of a dust devil. Since the main requirements for development of such features are the presence of dust and a warm ground, we focus our monitoring of dust devils in regions on Mars that are known to be dusty (like Syria Planum), and during the late spring and summer time, when we expect the ground to be warm.
The white dot just to the east of the Claritis Fossae mountain and fissure chain marks this channel’s location in the overview map to the right. In the May 2, 2023 cool image post, my focus had been the 1,100 foot high cliff wall on the north side of this ancient volcanic flow channel, noting that the channel itself had “a lot of dust, much of it likely volcanic ash. In the full picture are several ancient craters, all of which are almost entirely buried by this dust and ash.”
It seems the scientists decided to revisit this site because of its location and the quantity of dust, in the hope of catching a dust devil. They succeeded. Though they haven’t yet calculated the height of this dust devil, based on the length of the shadow it appears it is likely higher than that thousand-foot-high cliff.
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