On May 16th, 2017 we learned about

Smooth streaks surrounding Martian craters suggests violent vortexes were created during impacts

What’s cooler than a huge asteroid impact on another planet like Mars? How about an asteroid hitting Mars hard enough to produce giant tornadoes that scoured the surrounding area with 500 mile-per-hour winds? This dramatic scenario may sound like a set-piece for an upcoming Michael Bay movie, but it was actually put together in a simulation based on thermal infrared images taken by the Mars Odyssey orbiter. Beyond scrubbing the red planet’s surface, these winds may have also left clues about the nature of the asteroids that caused them in the first place.

Detected in the dark

As impressive as these tornadoes must have been when they occurred, nobody has observed any of these tornadoes directly, and even the trace evidence of them has only seen at night. As the orbiter passed over the dark side of Mars, it still took infrared images that captured how much heat was being emitted by the planet’s surface. While you’re not going to see what color a feature is, the amount of heat emitted at night can describe what the texture of that area looks like, with blocky objects shedding more heat than rough powders or debris. So these night-time heat images can be used to build a sort map of all the different surfaces and textures, some of which turned out to make some very interesting patterns near impact craters.

Large streaks of smoothed ground were detected radiating out from impact craters, which is what caught researchers’ eyes. They looked a bit like patterns that projectiles create in the air when being fired out of a cannon, which isn’t a bad analog for an asteroid hitting a planet. The patterns weren’t always perfectly consistent though, which, with the help of computer simulations, was partially explained by the topography near the craters.

Whipping up wind

According to simulations, the asteroids or comets likely hit the ground and were instantly vaporized, taking the material at the point of impact with it. Huge, powerful vapor traveled outwards (again, think Michael Bay explosions here,) skirting along over the surface of the planet at supersonic speeds. All that heat and motion would drum up winds in the Martian atmosphere, which would stir things up but not actually scour the ground like a tornado. For that, the winds and vapor plumes would need to run into slightly elevated features which would disrupt their movement and lead to a vortex that would scrape along the ground like an F8 tornado.

The need for specific elevations helps explain the frequency of these tornado streaks to a certain extent, but they’re still not as common as they might be if bumpy terrain were the only required ingredient (beyond the asteroid or comet, of course.) This suggests that the material that makes up the ground or the asteroid itself may be a competent to this phenomenon, with something like ice behaving differently than iron, for instance. If this can be pieced together, it may offer a new way to build the history of what’s been hitting Mars, or what Mars looked like, back when these impacts took place ages ago.

Source: Ancient Mars impacts created tornado-like winds that scoured surface, Scienmag

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