Windy Mars

There was some interesting discussion about dust devils yesterday. Spirit has been seeing more and more of them. The dust devils typically have diameters from 10 - 200 m and move horizontally at a speed of about 1 - 5 metres per second. However their height isn't yet known as the top hasn't been caught in the images and their rotation rate can't be measured on images taken 20 seconds apart. Answers on a postcard if you come up with an idea on how Spirit can work out their rotation rate.

The dust devils seem to peak around Martian noon as you might expect because they get their energy from the Sun. On sol 486, when Spirit was looking north-west, it spotted a dust devil moving the wrong way! By wrong way I mean that it wasn't moving in the same direction as the wind streaks that are visible on the surface. Having said that, recently the wind has been picking up and now that the dust devils are stronger, they do seem to be moving parallel to the wind streaks.

Those winds can be useful too. Spirit landed with 950 Watt hours and this started dropping to dangerously low levels as sand covered the solar panels. Luckily, a strong wind storm cleaned the panels and Spirit now has 950 Watt hours; more power than it had when it landed!

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Posted in astro blog by Stuart on Wednesday 07th Sep 2005 (14:41 UTC) | Permalink
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