Use of non-science engineering data from NASA’s Curiosity rover has allowed researchers to measure the density of the 96-mile wide Gale Crater on Mars.
“What we were able to do is measure the bulk density of the material in Gale Crater,” says Travis Gabriel, a graduate student in ASU’s School of Earth and Space Exploration. He worked on computing what the grain density should be for the rocks and ancient lakebed sediments the rover has been driving over.
“Working from the rocks’ mineral abundances as determined by the Chemistry and Mineralogy instrument, we estimated a grain density of 2,810 kilograms per cubic meter,” he says. “However the bulk density that came out of our study is a lot less — 1680 kilograms per cubic meter.”
These figures show that the rocks have a reduced density most likely resulting from the rocks being more porous. This means the rocks have been compressed less than scientists have previously thought.
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The sensors used in this study were accelerometers and gyroscopes like those found in modern smartphones. In a phone, their function is to determine its orientation and motion. Curiosity’s sensors do the same, but with much greater precision, helping engineers and mission controllers navigate the rover across the martian surface.
But while the rover is standing still, the accelerometers also measure the local force of gravity at that spot on Mars.
The team took the engineering data from the first five years of the mission — Curiosity landed in 2012 — and used it to measure the gravitational tug of Mars at more than 700 points along the rover’s track. As Curiosity has been ascending Mount Sharp, the mountain began to tug on it, as well — but not as much as scientists expected.
“The lower levels of Mount Sharp are surprisingly porous,” says lead author Kevin Lewis of Johns Hopkins University. “We know the bottom layers of the mountain were buried over time. That compacts them, making them denser. But this finding suggests they weren’t buried by as much material as we thought.”
The new findings suggest Mount Sharp’s lower layers have been compacted by only a half-mile to a mile (1 to 2 kilometers) of material — much less than if the crater had been completely filled.
“There are still many questions about how Mount Sharp developed, but this paper adds an important piece to the puzzle,” said Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, which manages the mission. “I’m thrilled that creative scientists and engineers are still finding innovative ways to make new scientific discoveries with the rover.”
Gabriel adds, “This is a testament to the utility of having a diverse set of techniques with the Curiosity rover, and we’re excited to see what the upper layers of Mount Sharp have in store.”