NASA's Curiosity rover makes unexpected discovery on Mars mountain

Mindy Sparks
February 2, 2019

NASA's Mars rover Curiosity carries a set of accelerometers normally used for navigation and attitude determination.

Gravimetry - the measurement of tiny changes in gravitational fields - can be used to probe the internal structure of Earth and other planets. Image credit: NASA / JPL-Caltech / MSSS. By examining variations in gravity, they can calculate the density of the underlying rock, revealing all sorts of things about its history. The nuclear-powered rover has highly sensitive accelerometers, and the aforementioned boffins were able to repurpose these to measure gravity on Mars.

The much lower figure shows that the rocks have a reduced density most likely resulting from the rocks being more porous. And scientists have realized those instruments can be recalibrated to help Curiosity measure Mars' gravity. But because the satellites are so far away from their targets, the spatial resolution is limited. Curiosity's sensors do the same, but with much greater precision, helping engineers and mission controllers navigate the rover across the martian surface. Scientists now think the rock would have compacted more if that was the case. 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.

But a way of hacking the rover's existing tools to get some new types of data has allowed it to make fresh discoveries about its home.

"What we were able to do is measure the bulk density of the material in Gale Crater", said geologist Travis Gabriel, a graduate student in Arizona State University's School of Earth and Space Exploration.

First, the researchers took into account Mars' rotation to accommodate expected changes in acceleration.

The results were also compared to mineral-density estimates from Curiosity's Chemistry and Mineralogy instrument, which characterizes the crystalline minerals in rock samples by using an X-ray beam. But I started looking into the data and calibrating out some of the complicating factors, like temperature and some other variables. From this data, the scientists estimated the density of rock in the mountain at 1,680 kg (about 3,704 pounds) per cubic meter. If so, they might have weighed heavily on the materials at the base, compacting them.

Planetary scientists have long debated the origin of Mount Sharp.

There are other craters on Mars with central peaks, raised by the impact that formed the crater.

According to a new study published January 31 in the journal Science, the Mars mission team may have figured out how a huge mountain on the Red Planet's surface called Mount Sharp may have formed.

However, the team now says that their findings suggest the mountain wasn't buried as much as they had thought. But the upper layers of the mound appear to be made of wind-scoured sediments more easily eroded than rock.

As Curiosity roved the dusty basin of Gale Crater, the instrument sensed that the sediment underneath is porous.

"There are still many questions about how Mount Sharp developed, but our study adds an important piece to the puzzle", said Dr. Ashwin Vasavada, Curiosity project scientist at NASA's Jet Propulsion Laboratory. Thus, the layers of rock that make up the mountain aren't as dense as was once expected and the theory that Gale Crater was once filled with sediment is unlikely.

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