Incoming meteors cause airbursts and avalanches on Mars
New Scientist has a fascinating story this morning (December 2, 2011) about avalanches of dust on Mars seen by orbiting spacecraft. They’re thought to be caused by meteors penetrating the Red Planet’s thin atmosphere, creating craters, yes, but also shock waves in the Martian atmosphere that spread across an area about a million times larger than the craters themselves.
You can find this study online today here. It’s part of the January 2012 edition of the journal Icarus.
NASA’s Mars Reconnaissance Orbiter spots about 20 new craters on Mars each year. The craters are between 1 and 50 meters across (3 to 150 feet). Closer scrutiny of the spacecraft images revealed thousands of small avalanches near 16 of the craters, thought to be caused by the shock waves in the Martian atmosphere, created by incoming meteors.
The avalanches discovered by the Mars Reconnaissance Orbiter appear as dark streaks on the hilly terrain that surrounds the craters. They show up only in areas where there is a lot of light-coloured dust on the ground. To form, it seems the surface’s dust coating was shaken loose and slid downhill, revealing the darker rocks beneath.
We all know Earth is geologically active, with active earthquakes and volcanoes, and plus we have winds and water, not to mention life. Earth is a world of change. That’s one reason avalanches on Mars are so much fun. I can remember a time just a few decades when the other walkable worlds in our solar system – Mercury, Venus, Mars and the moons of the outer planets – were assumed to be “dead” in comparison to Earth. At that point, there was little evidence for any sort of movement on their surfaces, with the exception perhaps of seasonal changes seen to cross the face of Mars, now known to be caused in part by planet-wide dust storms that kick up every two years, when Mars is closest to the sun in its orbit.
How stunned we all were in 1979 when the Voyager 1 spacecraft found active volcanoes on Jupiter’s moon Io! It was like pointing a finger at a dead rock and saying, “It lives!”
Today, with spacecraft in orbit around our neighboring world Mars and other worlds in our solar system, we’re able to see all sorts of change on other worlds. That includes shifting sand dunes on Mars and … avalanches. Isn’t the picture above wonderful? Wouldn’t you love to go there and see it?
Bottom line: Orbiting spacecraft have now seen avalanches of dust on Mars. They’re thought to be caused by meteors penetrating the Red Planet’s thin atmosphere, creating shock waves in the Martian atmosphere that spread across an area about a million times larger than the meteorite craters. Images from NASA’s Mars Reconnaissance Orbiter revealed thousands of small avalanches near 16 of Martian meteorite craters.