Published: Sun, February 03, 2019
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NASAs Curiosity finds Mars rocks more porous than expected | #96423

NASAs Curiosity finds Mars rocks more porous than expected | #96423

NASA's Curiosity rover had been studying Mars for years before a scientist thought of using it for something new: making the first surface gravity measurements on a planet other than Earth. Using the fact that gravitational fields weaken as altitude and distance from a planet's core increase, Lewis and team mapped out the gravitational field strength at more than 700 points from where Curiosity landed on the crater's floor up to where it had traveled into Mount Sharp's foothills.

Details on the new measurements, which researchers based on scientific analysis of data the rover already produced for navigation and engineering purposes, appear in the journal Science.

"The lower levels of Mount Sharp are surprisingly porous", Kevin Lewis, lead study author and assistant professor at Johns Hopkins University's Department of Earth and Planetary Sciences, said in a statement.

The little Curiosity rover sent us a new 'selfie, ' taken from the surface of Mars.

Scientists can learn a lot about a planet by measuring what lies beneath the surface at a particular location. In turn, this let the team calculate the density of the rock. In addition to the overall pull of Mars' gravity, higher density rocks in the subsurface exert a slightly greater downward gravitational force than lower density rocks.

This allowed the researchers to measure the density of the rock underneath Curiosity's wheels. But because the satellites are so far away from their targets, the spatial resolution is limited. Mars craters the size of Gale have central peaks raised by the shock of the impact that made the crater.

This limitation frustrated Lewis.

A team of researchers from NASA's Jet Propulsion Laboratory, John Hopkins University, Carnegie Institution, University of Maryland, and Arizona State University, all in the U.S., were responsible for calibrating the Curiosity's accelerometers for gravimetry.

"There's all sorts of ways you can use the rover, which is essentially a big complex box of electronics", he says.

"Curiosity, essentially, has a new science instrument six-and-a-half years into its mission..."
To their surprise, the rock was less dense than expected, according to the rejigged sensors. These were calibrated to filter out "noise", such as the effects of temperature and the tilt of the rover during its climb.

Gabriel worked on computing what the grain density should be for the rocks and ancient lake-bed sediments the rover has been driving over. They found that Mount Sharp, a peak in the middle of the Gale Crater, is much less dense than previously predicted, raising questions about the popular theory of how it developed. The nuclear-powered rover has highly sensitive accelerometers, and the aforementioned boffins were able to repurpose these to measure gravity on Mars.

When sediments are first deposited by geologic processes, they typically contain lots of empty space.

Scientists have long debated the origin of Mount Sharp. The new findings suggest Mount Sharp's lower layers have been compacted by only one to two km of material, much less than if the crater had been completely filled.

Going forward, there might be even more coming from Curiosity and its newest instrument.

"To me, Mars is the uncanny valley of Earth", Lewis said.

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