More data, better picture

For this new study, researchers trained a neural network to recognise dust devils and then comb through images taken by Mars Express since 2004 and ExoMars TGO since 2016 to build up a catalogue of 1039 of them.

The map above shows the locations of all 1039 dust devils, and the direction of motion for 373. It confirms that although dust devils are found all over Mars, even on its towering volcanoes, lots are swept up from certain ‘source regions’. For example, many were clustered in Amazonis Planitia (upper left of the map), a huge patch of Mars covered in a fine layer of dust and sand.

By tracking how fast the dust devils moved, the researchers found wind speeds of up to 44 m/s, or 158 km/h. This is faster than we’ve ever measured with rovers on the ground – though it’s worth noting that the martian air is so thin that a human would barely even notice a wind of 100 km/h on Mars.

The researchers found that, in most cases, the dust devils were being blown across the landscape faster than our current Mars weather models predicted. In places where wind speeds are higher than expected, there may be more dust being lifted from the ground than we realised.

Like Earth, Mars has seasons. The catalogue also highlights that dust devils are most common in the spring and summer of each hemisphere. They last a few minutes and typically happen during the daytime, peaking between about 11:00 and 14:00 local solar time.

This is very similar to what we see on Earth, where dust devils are most common in dry and dusty places in the late morning to early afternoon during the summer months.