Mars has a lot of visible craters on the surface. But some are rather peculiar, in that they have streaks moving away from the center, something we don’t really see anywhere else.
Now a pair of researchers has provided a possible answer. They suggest some ancient impacts on Mars may have produced extremely powerful winds that scoured the surface. And they may help us get an insight into the climate history of Mars.
"This would be like an F8 tornado sweeping across the surface," Peter Schultz, a geologist at Brown University said in a statement. "These are winds on Mars that will never be seen again unless another impact."
Schultz conducted the research with graduate student Stephanie Quintana. Their research is published in the journal Icarus.
They studied craters on Mars that had these strange streaks. Using infrared images of the craters taken during the nighttime by the THEMIS (Thermal Emission Imaging System) instrument on the Mars Odyssey spacecraft, they saw that something must have come along and scoured the surfaces.
The culprit is thought to be what happens after an asteroid or other body strikes the surface. When it hits at high speed, a huge amount of material from the asteroid and the ground is instantly vaporized.
In experiments, Schultz showed that this creates vapor plumes that travel outward at supersonic speeds. Interacting with the Martian atmosphere, these would create tornado-like winds that swirled at 800 kilometers (500 miles) per hour.
"Where these vortices encounter the surface, they sweep away the small particles that sit loose on the surface, exposing the bigger blocky material underneath, and that's what gives us these streaks," Schultz said in the statement.
The streaks extend 10 kilometers (6 miles) or more from the craters in each direction. But interestingly they only form around certain craters, which may be due to the impactor being a comet, or could be linked to material on the surface at the time of the impact.
For example, water ice on the surface can affect the amount of vapor that escapes during the impact. Most of the streaks are found around smaller craters inside larger ones, suggesting ice had been exposed prior to a second impact. So it’s possible these streaks may be a sign that ice was present in these regions at the time of the impact.
This may, in turn, help us paint a picture of the ancient Martian climate. We think it may have gone through one or multiple wet periods, before it’s atmosphere was lost and the water boiled from the surface. Ice is thought to still reside underground – and may ultimately be the cause of these streaks, in tandem with tornado-like winds.