After nearly seven years of crossing the surface of Mars, NASA’s Curiosity rover has unexpectedly managed to add another science instrument.
Prior to any important space exploration mission, the design team labours tirelessly to make sure that the rover or spacecraft it is sending (which will never return) can carry as many scientific instruments as possible. So, it comes as a welcome surprise that it is possible to remotely add another scientific instrument to the Curiosity rover nearly seven years after it arrived on Mars.
Publishing their findings in Science, researchers from Johns Hopkins University revealed that they have used Curiosity – currently navigating the Gale Crater – to collect the first surface gravity measurements of another planet, despite the rover never being designed to do so.
By examining variations in gravity on a planet, researchers can calculate the density of the underlying rock, revealing a great deal about the area’s history. As it had already collected hundreds of measurements over nearly seven years of exploration, Curiosity could be used to measure subtle changes in gravitational acceleration.
Typically, to measure gravity on other planets such as Mars, scientists rely on satellites – such as the Mars Reconnaissance Orbiter – in orbit. However, the amount of data they can gather is limited. For example, researchers can barely make out Gale Crater – with its 150-kilometre span – in the satellite gravity data of Mars.
Lead author of the latest study, Kevin Lewis, admitted being frustrated by this limitation, which set him on a challenge to calibrate Curiosity’s engineering accelerometers to measure surface gravity as it climbed the 5km-high Mount Sharp. Much like accelerometers in smartphones, Curiosity’s ones help it determine its position and also assist in navigation.
‘All sorts of ways you can use the rover’
First, the team took into account Mars’s rotation to accommodate expected changes in acceleration. Next, they calibrated this raw information, accounting for the effects of temperature, the tilt of the rover and other factors.
The most surprising find was that Curiosity was above low-density rock, given that its CheMin instrument – used to determine a rock’s mineralogy – showed the area to have highly porous rocks. As rocks get buried deeper and deeper over time they become more compacted and dense, but this new analysis showed them to be younger in age.
It was previously suggested that the Gale Crater was once completely filled by sedimentary rock, with Mount Sharp (found within) being carved out of these layers of sediment by erosion. This new finding, however, suggests this isn’t the case and that the layers of Mount Sharp never completely filled the crater.
One explanation is that the upper layers of the mountain formed by wind-driven processes rather than in a lake.
“There’s [sic] all sorts of ways you can use the rover, which is essentially a big complex box of electronics,” Lewis said. “There may still be new science instruments waiting to be discovered on Curiosity.”