Top Ten Astronomy Pictures of 2009

By Phil Plait | December 15, 2009 6:00 am




#2: The Detail’s in the Devil

It’s easy to think of Mars as a dead world. Cold, small, and dry, it seems unchanging through our telescopes.


Mars has an atmosphere, though it’s thin: about 1% of Earth’s atmospheric pressure, it doesn’t seem capable of doing much. But when you have a robotic probe like the Mars Reconnaissance Orbiter and its 50-cm resolution orbiting the Red Planet, you see far, far more, and learn that the air of Mars can create beauty.

The image above shows a region of Mars near its mid-lower northern latitudes. It’s a close-up of the bed of a crater, and you can see the ripples of sand dunes, endemic on the Martian surface. The sand is similar to beach sand here on Earth, but is dark in color because it’s made of basalt, a greyish rock. Then why is Mars so red? It’s because of much finer-grain dust, which is reddish in hue. The dust lies on top of the sand, making everything look red.

But then there’s that thin Martian air. Rising heat from the plains can blow through cooler air above, forming vortices like mini-tornadoes called dust devils. These then roll across the surface, picking up the lighter red dust but leaving behind the heavier, darker sand grains. What remains, as seen from above, are these gorgeous swirls, the fingerprints of the geology and weather of Mars.

This image has a resolution of about a meter per pixel, and is only a half kilometer (.3 miles) across. The detail in it is phenomenal! It makes me wonder what it would look like to actually soar above the surface of Mars in a glider, tipped and tilted by the vagaries of the Martian winds. But then, it probably looks just like this. With less airsickness.

Original news story (with muchly embiggened version)

BA Blog post

Credit: NASA/JPL/University of Arizona



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