The Mars rovers are some of mankinds’ farthest-traveling machines. With four successful Mars rovers, each more advanced than the next, they are making important discoveries about Mars’ atmosphere, surface, geology and environment.

Currently, the most recent Mars rover, named Curiosity, has made a recent discovery about Mount Sharp.

This discovery was made when Curiosity weighed Mount Sharp, learning that the mountain was built in two phases. One was characterized by extreme wetness and the other was characterized by high amounts of aridity.

The rover discovered this information because it found that rocks beneath its wheels were less densely packed than previously thought. This suggests that the mountain was not just formed from compressed lake sediments.

Kevin Lewis, a planetary scientist at Johns Hopkins University, reported, “I had no idea what to expect. This is the first measurement of its type on Mars.”

Curiosity landed on Mars in 2012 in the Gale Crater, which, based on inital hypotheses, may have been a lake at one point. 753 Martian days later, Curiosity began climbing Mount Sharp, or Aeolis Mons, at the lake’s center.

“Mount Sharp is a big puzzle,” says Lewis. “One hypothesis is that the mountain was deposited layer by layer within the ancient lake, until it eventually filled the entire crater. The weight of all those layers of rock would densely compact the rocks at the base.”

Another prevailing theory based on some unusual features are that the wind carried sand and dust particles, building up Mount Sharp.

Using the on-board accelerometer, Lewis and his colleagues have been able to measure the density of the rocks that make up Mount Sharp.

Initial thoughts were based on the rocks’ mineral composition, which was actually less dense. This supports the theory that wind-driven build up helped create Mount Sharp.

This shows that two periods, one of extreme wetness and the other of extreme dryness, created Mount Sharp and expanded our knowledge of our Martian neighbor.