Keynes (UK), December 15
A dust devil looks a bit like a tornado, but is weaker and rarely lasts more than about a minute.
It is a twisting column of warmed air scooting across sun-heated ground, made visible by the dust that it lofts upwards. Although usually benign, occasionally dust devils can kill.
Dust devils have been known to appear on Mars since the 1970s. They have been observed both from the ground and from orbit.
The more dust in the Martian atmosphere, the warmer and more agitated it becomes, and this can escalate into a global dust storm.
