Dust storm to the South

As I said in a previous post, it's southern spring turning summer and this is when we should expect dust storms to form usually starting from the south. The reason for this is that Mars' orbit is such that it closest to the sun during southern solstice (that is southern summer) than any time of the Martian year. This means more solar energy hits the Martian surface, creating atmospheric instabilities that give birth to storms that may be regional or global in size.

Global mosaic made by the Mars Reconnaissance Orbiter's colour imager for daily weather imaging. The landing sites of the operational rovers are marked. The dust storm's boundaries are demarcated with white arrows, occupying the Hellas basin and Promethei regions to the south (NASA/JPL-Caltech/MSSS)

This storm was tracked from the northern hemisphere as it descended south to its current position (up going down in the mosaic above) where it settled and and is now growing. This is so far a regional storm but already the skies are darkening a little at Meridiani planum where Opportunity is and Curiosity is reporting a drop in pressure and elevated night temperatures (the extra dust in the skies traps more heat which elevates temperatures). Curiosity is nuclear-powered and has only to accomodate warmer ambient temperatures than usual but Opportunity is solar-powered and might suffer from a loss of solar power. For an idea of what its like under such storms, see the montage of images below from Opportunity during a global storm in 2007.

The symbol above is tau and represents atmospheric opacity (Commons/NASA/JPL)

Now this is all just dust and not sand or anything sind-sized because Mars' atmosphere is too thin to lift these materials in to the air for an extended period of time. But despite that, these storms can do damage to hardware and potentially humans (fine aerosols in the air might cause lung irritation or even cancer) so understanding how to predict when and which regional hiccups can cause global wipe outs would be great. Welcome to Mars folks! We can expect sunny and dry spells interspersed with showers of dust and snow (I'm not kidding, it actually SNOWS on Mars).

Visit the Malin Space Science Systems site for a weather report on the current storm.