Mars may be pretty low on traffic these days but, on this day back in 2005, NASA’s Spirit rover (the twin to Opportunity) seemed to find itself at a busy intersection as several blustery dust devils zipped past, one after the other!
The animation above is an edited version of one released by NASA’s Jet Propulsion Laboratory around the time the scene was captured. It’s been contrast-adjusted to bring out the detail in the dust devils against the dark surface material of the landscape within Gusev Crater, where Spirit (MER-A) explored from 2004 to 2010. A Mars-like color tint has also been added. (See the original version here.)
This particular dust devil swarm was observed on July 13, 2005, which was mission sol 568 for Spirit. The actual time elapsed across the individual frames above was about 12 minutes.
Dust devils on Mars are common, especially during local spring. Just like on Earth they’re caused by heated air just above the surface rising rapidly upwards in spinning columns, picking up dust and sand and propelled forward by prevailing wind. But although relatively gusty by speed measurements, even high-velocity winds on Mars would hardly be felt by humans because of the very low air density (about the same as what’s found 35 km / 22 miles above sea level here.) Still, dust devils manage to carve twisting tracks across Mars’ dunes and on occasion even came in handy as visiting cleaners of dusty rover solar panels.
Dust devils aren’t the same as tornadoes, although sometimes they can grow large enough to resemble them. On Mars, where both air pressure and gravity are lower than on Earth, they have been spotted by the Mars Reconnaissance Orbiter’s HiRISE camera reaching as high as 20 kilometers (12 miles)!
This wasn’t the first time Spirit had captured images of dust devils; it spotted quite a few others as well around the same time period, with different cameras too. You can see more of Spirit’s animated dust devil photography here.
While the devils are still very likely active all around it, the Spirit rover won’t be taking or sending any more pictures. It fell silent in March 2010 after getting stuck near a feature called Home Plate, and although all attempts were made to re-establish communication it was never heard from again. Its mission was declared officially over on May 25, 2011 — seven years, eleven months, and thirteen days after its launch.
Spirit’s twin Opportunity continued its own roving exploration adventure elsewhere on Mars for another eight years until a planet-wide dust storm shut it down permanently in June 2018, over 14 years after its arrival on Mars.
Currently Curiosity and InSight are the only active robots on the surface of Mars, but that will change in February 2021 when NASA’s Mars 2020 Perseverance rover, along with the Ingenuity helicopter, arrive in Jezero Crater.