Shift Happens: Mars May Have Plate Tectonics
Mars has suddenly gotten more interesting thanks to a science sleuth who combined his knowledge of the Himalayas with photo reconnaissance of the Red Planet.
UCLA scientist An Yin reports that Mars may be the only other planet in the solar system with plate tectonics.
Since the middle of the last century we've known that Earth's crust is broken into several dozen plates bumping and grinding to make mountains and power chains of volcanoes, which recycle surface material and control the carbon dioxide balance in our atmosphere.
By comparison, Mars has a mobile yet very sluggish crust divided into just two plates Yin says, “Mars is at a primitive stage of plate tectonics. It gives us a glimpse of how the early Earth may have looked."
One of the biggest surprises from our first orbital reconnaissance of Mars in 1971 was the discovery of the solar system's largest canyon system, which would stretch from Los Angeles to News York, and is five times the depth of the Grand Canyon in Arizona.
The origin of this “grandest canyon" — called Valles Marinaris after the NASA orbiter Mariner 9, — has been a puzzle over the past 40 years. Some suggestions are that it is just a big crack that opened up on the Martian surface. A more recent theory proposes that it formed from a giant collapse when salts were heated up and released water that rushed out through underground channels.
Yin's conclusion is based on analyzing over 100 images of the great canyon taken by the High-Resolution Imaging Science Experiment (HiRISE) aboard NASA's Mars Reconnaissance Orbiter. Collectively, the photos resemble faults he's seen in the Himalayas and Tibet, not to mention California.
Yin calls the two plates Valles Marineris North and the Valles Marineris South (shown below). This theory would explain the dramatic landslides seen along the canyon walls. The two plates divided by Mars' Valles Marineris have moved a total of 93 miles horizontally relative to each other, Yin reports, and are similar to California's San Andreas Fault, which is over the intersection of two plates.
Because Mars is smaller that Earth it has long been surmised that the core is cooler and the crust too thick for plate tectonics. Also, it's thought that an ocean is needed to lubricate plate motion; otherwise the crustal slipping and sliding grinds to a halt like an auto engine without oil. Mars' core is smaller and therefore must be cooler than Earth's, so there is much less thermal energy to drive the motion of the plates.
Where plate tectonics on Earth drives horrendous earthquakes, on Mars a quake might come along every 1 million years Lin says. So future colonists on the Red Planet won't really need earthquake, or rather Marsquake, property insurance.
Image credit: NASA, Yin/Google