Washington: Meteorites trigger avalanches on Mars before they even hit the ground of the Red Planet, finds a new study.
Researchers at the University of Arizona found that space rocks flying towards the Martian surface can travel at several times the speed of sound, creating shockwaves in the air.
These shockwaves pummel the ground, kicking up dust that rolls over slopes in dark streaks that can be seen from orbit, the scientists said.
"We expected that some of the streaks of dust that we see on slopes are caused by seismic shaking during impact," Kaylan Burleigh, an Arizona undergraduate who led the research, was quoted as saying by LiveScience.
"We were surprised to find that it looks like shockwaves in the air trigger the avalanches even before the impact."
For their research, Burleigh and his team analysed dark streaks seen in images by NASA`s Mars Reconnaissance Orbiter, and found that many did not fit the pattern expected if they were caused by the seismic shaking produced by the impact of a space rock.
Instead, these streaks bore signatures of shockwaves that would have been created before any impact occurred.
Indeed, Burleigh said, when they used a computer model to simulate the geologic features expected from such shockwaves, they found characteristic curved marks, called scimitars, exactly matching those seen on the surface of Mars.
"Those scimitars tipped us off that something other than seismic shaking must be causing the dust avalanches," he said.
Mars is regularly barraged with meteorite impacts. The planet`s thin atmosphere is 100 times less dense than that of Earth and cannot shield the surface from even small space rocks. On average, scientists spot about 20 new impact craters between 3 and 165 feet wide every year.
"This is one part of a larger story about current surface activity on Mars, which we are realising is very different than previously believed," said co-author Alfred McEwen.
"We must understand how Mars works today before we can correctly interpret what may have happened when the climate was different, and before we can draw comparisons to Earth."