NASA’s Curiosity rover has been busy measuring Mars, and it’s using smartphone-like sensors to complete its mission. The agency has been using accelerometers and gyroscopes — like the ones that detect the tilt of your phone and rotate the screen — to understand its location and orientation. These sensors, while designed for navigation, have played an unexpected role in measuring the size of mountains.
The team was able to repurpose the sensors on the rover, which has been roaming the planet for the past seven years, and use them to create a makeshift “gravimeter.” This is a tool used by the Apollo 17 mission back in 1972 to determine the changes in gravitational pull, enabling the mission to capture 25 measurements of the Taurus-Littrow Valley on the moon. By repurposing the sensors on Curiosity to capture the same measurements, scientists were about to drive across Mars’ Mount Sharpe and make some surprising discoveries.
“The lower levels of Mount Sharp are surprisingly porous,” lead author Kevin Lewis of Johns Hopkins University said in a statement. “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 team captured more than 700 measurements from October 2012 and June 2017, filtering out the data based on expected gravitational pull and the effect of temperature on the surface. The scientists have documented their findings in a research paper titled “A surface gravity traverse on Mars indicates low bedrock density at Gale crater,” published in Science on Friday.
“There are still many questions about how Mount Sharp developed, but this paper adds an important piece to the puzzle,” said study co-author Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “I’m thrilled that creative scientists and engineers are still finding innovative ways to make new scientific discoveries with the rover.”
It’s not the first time scientists have repurposed Curiosity’s key components. When a drill broke down in 2016, NASA reprogrammed the rover to push the component down like a human-held hand drill, bypassing the two metal rods that stopped functioning. Curiosity also celebrated its sixth birthday by using its camera to take a selfie.
Read the paper’s abstract below:
Gravimetry, the precise measurement of gravitational fields, can be used to probe the internal structure of Earth and other planets. The Curiosity rover on Mars carries accelerometers normally used for navigation and attitude determination. We have recalibrated them to isolate the signature of the changing gravitational acceleration as the rover climbs through Gale crater. The subsurface rock density is inferred from the measured decrease in gravitational field strength with elevation. The density of the sedimentary rocks in Gale crater is 1680 ± 180 kilograms per cubic meter. This value is lower than expected, indicating a high porosity and constraining maximum burial depths of the rocks over their history.