'Terraces' in Badger Crater Lead to Discovery of Mars Ice Sheet
Imagine this ...
You see a picture of a crater and what immediately pops into mind?
A steeply sided, bowl-shaped depression, right?
So what would you think when you find a crater that looks completely different? Like when you find a crater that isn't bowl-shaped but has terraces instead?
Craters should be bowl shaped, but this one had terraces in the wall.
It was this strange shape that caught Ali Bramson's eye when she looked at Badger Crater, which at 710 meters in diameter is just one of several terraced crates in Arcadia Planitia, a fairly flat region in the mid northern latitudes of Mars.
Bramson, a graduate student in the University of Arizona's Lunar and Planetary Laboratory (LPL), noted the strange shape of Badger Crater, but a couple of quick calculations helped explain the weird shape. As she explained:
When the crater is forming, the shock wave from an object hitting a planet’s surface propagates differently depending on what substrates are beneath the area of impact. If you have a weaker material in one layer, the shock wave can push out that material more easily, and the result is terracing at the interface between the weaker and stronger materials."
In other words, terraces can form when there are layers of different materials in the planet’s subsurface, such as dirt, ice or rock.
Using the Mars Reconnaissance Orbiter’s High Resolution Imaging Science Experiment, or HiRISE, camera, which is operated out of LPL, Bramson and her colleagues created three-dimensional models of the area's craters, which allowed them to measure the depth of their terraces.
The researchers then combined that data with the MRO’s Shallow Radar, or SHARAD, instrument to measure the surface’s layers.
What did they find?
Ice - and lot's of it.
130 feet thick and covering an area the size of California and Texas combined, this enormous slab of ice sits just below the surface.
Scientists have known for a long time about the presence of ice at Mars' poles, but the ice in Arcadia Planitia - -and the sheer size of the ice sheet -- were a bit if a surprise to Bramson her colleagues. Its age, size and location were something completely new -- and what makes this compilation such an intriguing 'Mars Picture of the Week' (OK -technically it's a rendering, but still pretty cool!).
To help explain her findings, Bramson even created a quick 'flyover' video showing the detail of Badger Crater. Take a look for some truly amazing imagery!