It’s not every day that NASA’s Perseverance rover observes a series of objects moving across the Martian landscape. Even stranger is when one appears to consume the other right before the robotic explorer’s camera eye.
That’s just what happened earlier this year, as “Percy” watched from its position at the rim of Jezero crater as several dust devils manifested within its field of view. Suddenly, two of the nearest formations—which scientists call convective vortices—moved close to one another, with the larger of the two consuming its smaller sibling.
The rare occurrence was captured in a short video assembled by the Perseverance team from images taken with the rover’s navigation camera, which collects data about atmospheric conditions on Mars.
The Enigma of Martian Dust Devils
Comprised of fine particles of Martian dust swept up into swirling columns of air, the Martian dust devils are not uncommon features on the Red Planet. In 2023, Perseverance captured a similar display, showing one of the formations as it moved along in the distance.
However, the dust devils in NASA’s most recent video of the phenomenon are much larger than they appear. The larger of the two nearest vortexes was estimated to be close to 210 feet wide, with the smaller reaching a diameter of around 5 meters before being overtaken and “cannibalized” by the other.
“Convective vortices — aka dust devils — can be rather fiendish,” said Perseverance scientist Mark Lemmon at the Space Science Institute in Boulder, Colorado. “These mini-twisters wander the surface of Mars, picking up dust as they go and lowering the visibility in their immediate area. If two dust devils happen upon each other, they can either obliterate one another or merge, with the stronger one consuming the weaker.”
A Deeper Look at Convective Vortices
Like their Earthly counterparts, convective vortices occur when warmer air near the surface rises through cooler air above, which causes a rotating updraft. Surrounding air then rushes to fill the lower-pressure area, causing the column to spin faster.
“Dust devils play a significant role in Martian weather patterns,” said Katie Stack Morgan, project scientist for the Perseverance rover at NASA’s Jet Propulsion Laboratory in Southern California. “Dust devil study is important because these phenomena indicate atmospheric conditions, such as prevailing wind directions and speed, and are responsible for about half the dust in the Martian atmosphere.”
Given their frequent appearances, NASA has used its robotic explorers to study these “fiendish” phenomena for decades, going back to the 1970s with observations made by the Viking orbiters. The Pathfinder mission in the 1990s also captured imagery of one of the dust devils as it made its way over the lander.
Spirit, Opportunity, and Curiosity have each spotted the peculiar displays from their respective vantage points on the Martian surface over the years, which requires a bit of luck and being in the right place at the right time.
As for the cruel fate of the smaller dust devil in the recent video, Lemmon offered some assurance, joking that “it may give you some solace to know the larger perpetrator most likely met its own end a few minutes later.”
“Dust devils on Mars only last about 10 minutes,” Lemmon added.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.