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Moon and Mars
Mars doesn’t rumble any more, but it does rattle.
A robotic lander has measured hundreds of “marsquakes.” Most of them are puny. They’re probably generated in the crust — perhaps as the result of the planet cooling and shrinking.
But some quakes are a little stronger — up to about magnitude four. They probably come from deeper inside the planet — from the boundary between the crust and the mantle. Observations of a few of the quakes have been converted to sound.
Scientists have traced a few of the stronger quakes to a region a thousand miles from the lander. Cerberus Fossae consists of three long, deep “cracks” in the surface. The cracks run parallel to each other. They’re up to about 750 miles long, and a few thousand feet wide. They’re near the equator, to the southeast of a group of three giant volcanoes.
The volcanoes could be responsible for the cracks, which are only a few million years old. Lava flowing below the surface could have left voids that collapsed, for example. As the cracks formed, they could have released vast amounts of pressurized water or lava. The flowing liquid carved channels that aim away from the cracks — more activity around the most geologically active region on Mars.
Look for Mars near the Moon the next couple of mornings. They’re high in the sky at first light. Mars is to the upper left of the Moon tomorrow, and to the upper right on Sunday.