NASA’s Mars Reconnaissance Orbiter (MRO) has sent amazing images of Matara Crater on the Red Planet. The high resolution images showcase many gullies that run through the sand dunes in the Matara Crater region. As per NASA release earlier this week, gullies on Mars are different from those seen on Earth. The gullies on Mars are created by ‘freeze and thaw of carbon dioxide frost’.
Winter temperatures on the Red Planet condense carbon dioxide from a gas to a solid. These solid carbon dioxide blocks are then thought responsible for making gullies and furrows on Mars’ landscape, based on innovative lab experiments.
The images captured by MRO’s “High Resolution Imaging Science Experiment” camera (HiRISE) showcase many interesting features of the Red Planet for astronomers to study in detail. MRO was launched by NASA in 2005 and the project has offered valuable information about Mars. As MRO has lost control of its gyroscopes, it is difficult to ascertain which direction it is pointing towards.
Mars’ atmosphere is composed of over 95% CO2, yet we know little about how it interacts with the surface of the planet. Mars has seasons, just like Earth, which means that in winter, a lot of the CO2 in the atmosphere changes state from a gas to a solid and is deposited onto the surface in that form.
Linear gullies are another example of active Martian features not found on Earth. They are long, sometimes sinuous, narrow carvings thought to form by CO2 ice blocks which fall from dune brinks and ‘glide’ downslope.
The difference in temperature between the sandy surface and the CO2 block will generate a vapor layer beneath the block, allowing it to levitate and maneuver downslope, in a similar manner to how pucks glide on an ice-hockey table, carving a channel in its wake. At the terminus, the block will sublimate and erode a pit. It will then disappear without a trace other than the roughly circular depression beneath it.
Gullies on Martian sand dunes, like these in Matara Crater, have been very active, with many flows in the last 10 years. The flows typically occur when seasonal frost is present.
In this image from NASA’s Mars Reconnaissance Orbiter we see frost in and around two gullies, which have both been active before. (View this observation to see what these gullies looked like in 2010.) There are no fresh flows so far this year, but HiRISE will keep watching.
The map is projected here at a scale of 50 centimeters (19.7 inches) per pixel. [The original image scale is 50.3 centimeters (19.8 inches) per pixel (with 2 x 2 binning); objects on the order of 151 centimeters (59.4 inches) across are resolved.] North is up.