English: This image captured by the CaSSIS camera on the ESA-Roscosmos ExoMars Trace Gas Orbiter on 19 May 2021 features active dust devils northeast of Amazonis Planitia (35.2°N/210.1°E).

Dust devils usually appear as small vortexes and slightly bluer in CaSSIS false colour composite images like these. These dust vortexes often ‘clean’ the surface by removing a thin dust layer, leaving a dark trail behind known as a dust devil track.

Dust devils on Mars form in the same way as those on Earth: when the ground gets hotter than the air above it, rising plumes of hot air move through cooler denser air, creating an updraft, with the cooler air sinking and setting up a vertical circulation. If a horizontal gust of wind blows through, the dust devil is triggered. Once whirling fast enough, the spinning funnels can pick up dust and push it around the surface.

This image was acquired in the middle of spring in the northern hemisphere of Mars, a season that is characterised by increased dust devil activity. TGO arrived at Mars in 2016 and began its full science mission in 2018. The spacecraft is not only returning spectacular images, but also providing the best ever inventory of the planet’s atmospheric gases, and mapping the planet’s surface for water-rich locations. It will also provide data relay services for the second ExoMars mission comprising the Rosalind Franklin rover and Kazachok platform, when it arrives on Mars in 2023.

Credits: ESA/Roscosmos/CaSSIS, CC BY-SA 3.0 IGO