Wind, Not Water Formed Mount Sharp Within Mars' Gale Crater
May 6, 2013

Wind, Not Water Formed Mount Sharp Within Mars’ Gale Crater

Lee Rannals for — Your Universe Online

Scientists at Princeton University and the Caltech believe that Mount Sharp on Mars was formed by wind, not water.

NASA's Curiosity rover is sitting on Mars right now looking for signs of past life. The space agency chose Mount Sharp at the massive Gale Crater for its primary mission because of how eclectic the area is, potentially providing answers to questions regarding Mars' past.

Mount Sharp is a roughly 3.5-mile high Martian mound, and scientists previously thought the mountain preserved evidence of a massive lake. However, researchers reported in the journal Geology that the mountain formed as a result of the Red Planet's dusty atmosphere rather than a lake. This research could potentially dilute expectations that the mound holds evidence for a large body of water.

The team suggests the mound emerged as strong winds carried dust and sand into the 96-mile-wide crater in which the mound sits. They said air likely rises out of the Gale Crater when the Martian surface warms during the day, then sweeps back down its steep walls at night. These "slope winds" eventually died down at the crater's center where the fine dust in the air settled and accumulated to help form Mount Sharp.

Curiosity has helped uncover that Gale Crater contains traces of clay, water molecules and organic compounds. Determining the origin of these elements and how they relate to Mount Sharp is the focus of Curiosity's mission for the next few months. However, the scientists from the current study said the mound itself will not provide much information about Mars' wet past.

"Our work doesn't preclude the existence of lakes in Gale Crater, but suggests that the bulk of the material in Mount Sharp was deposited largely by the wind," said study co-author Kevin Lewis, a Princeton associate research scholar in geosciences and a participating scientist on the Curiosity rover mission, Mars Science Laboratory (MSL).

"Every day and night you have these strong winds that flow up and down the steep topographic slopes. It turns out that a mound like this would be a natural thing to form in a crater like Gale," Lewis said in a statement. "Contrary to our expectations, Mount Sharp could have essentially formed as a free-standing pile of sediment that never filled the crater."

He said these sedimentary mounds could record millions of years of Martian climate history.

"This is how we learn about Earth's history, by finding the most complete sedimentary records we can and going through layer by layer," Lewis added. "One way or another, we're going to get an incredible history book of all the events going on while that sediment was being deposited. I think Mount Sharp will still provide an incredible story to read. It just might not have been a lake."

Dawn Sumner, a geology professor at the University of California-Davis (UC Davis) and a Mars Science Laboratory team member, said the team's model of Mount Sharp helps explain the mound's origin.

"To my knowledge, their model is novel both in terms of invoking katabatic [cool, downward-moving] winds to form Mount Sharp and in quantitatively modeling how the winds would do this," said Sumner, who is familiar with the work but had no role in it. "This paper provides a new model for Mount Sharp that makes specific predictions about the characteristics of the rocks within the mountain. Observations by Curiosity at the base of Mount Sharp can test the model by looking for evidence of wind deposition of sediment."

Lewis said they could use their work to understand a lot more about Mars and how it operates, because Mount Sharp is only one of a class of enigmatic sedimentary mounds observed on Mars.