Episode 391 Valles Marineris

In today's episode we’re going to space. Specifically, Mars. You didn’t really think that earth science is really limited to the earth, did you? Our topic today will be the Valles Marineris.

The Valles Marineris is a long series of canyons east of Olympus Mons, the largest mountain in the solar system. These canyons are about 4,000 km long, 200 km wide and up to 7 km (23,000 ft) deep. On terrestrial scales, the Valles Marineris is as long as the distance from New York to Los Angeles. That’s about the same as Beijing to Hong Kong or Madrid to Copenhagen for our international listeners. They are as wide as central Florida, central Italy, or the middle of the Korean peninsula. Two and a half times deeper than Death Valley, though only about 60 percent of the depth of the Marianas Trench, the lowest point on earth.

Valles Marineris Image Courtesy NASA/JPL-Caltech

Not to be outdone, our planet, Earth, has even bigger valleys. These occur at the oceanic ridges, where plate spreading takes place. The longest rift valley on earth lies in the middle of the Mid-Atlantic Ridge, and it is more than double the length of the Valles Marineris. But let’s not belittle Mars. After all, while we have a pretty good idea for how oceanic rifts form on earth, there is quite a bit of debate about how Mars’ great valley formed.

The most popular theory suggests that the Valles Marineris are an analog to our oceanic rifts, and formed by the same process. As the volcanoes of the nearby Tharsis region developed, the Martian crust bowed down toward the center of the planet due to the weight of the new volcanic rocks. In time, the crust began to crack. This crack is what we see in the Valles Marineris. Unlike on Earth, this rift valley did not continue expanding, but shut down as the Tharsis Region, and Mars as a whole, cooled. Remembe