Some very clever people have figured out how to use MSL Curiosity’s navigation sensors to measure the gravity of a Martian mountain. What they’ve found contradicts previous thinking about Aeolis Mons, aka Mt. Sharp. Aeolis Mons is a mountain in the center of Gale Crater, Curiosity’s landing site in 2012.
Gale Crater is a huge impact crater that’s 154 km (96 mi) in diameter and about 3.5 billion years old. In the center is Aeolis Mons, a mountain about 5.5 km (18,000 ft) high. Over an approximately 2 billion year period, sediments were deposited either by water, wind, or both, creating the mountain. Subsequent erosion reduced the mountain to its current form.
Now a new paper published in Science, based on gravity measurements from Curiosity, shows that Aeolis Mons’ bedrock layers are not as dense as once thought.
Curiosity’s gravity measurements recall earlier days in Solar System exploration, when Apollo 16 astronauts used their Moon buggy, or Lunar Roving Vehicle, to measure the Moon’s gravity. That was way back in 1972. In our time, its robots instead of astronauts that are setting foot on distant worlds, but the spirit of exploration, and the science, is the same.
The new study is based on gravimetry, the measurement of very small changes in gravitational fields. It can only be done on the ground, versus large-scale gravimetry done from an orbiting spacecraft. To take these measurements, the research team re-purposed Curiosity’s accelerometers, instruments onboard the rover that are used for navigation.
When coupled with gyroscopes, accelerometers tell the rover where it is on Mars and which way it’s facing. Smart phones have them too, and they’re used by apps that allow you to point your phone at the sky and read the names of stars. Of course, Curiosity’s gyroscopes and accelerometers are far more accurate than anything inside a smart phone.
“I’m thrilled that creative scientists and engineers are still finding innovative ways to make new scientific discoveries with the rover.”
Study co-author Ashwin Vasavada, Curiosity’s project scientist, NASA’s Jet Propulsion Laboratory, Pasadena, California.