Scientists Shed Light on Mars Mountain Mystery
Researchers from John Hopkins University found a new way for the Curiosity Rover, which has been exploring the Gale Crater on Mars, to gather surface gravity measurements. Their findings were published in Science last week.
The scientists measured the density of sedimentary rocks under the Curiosity rover by analysing changes in the gravitational acceleration. On Earth, the acceleration of free fall is greater in areas where there are mountains or deposits of minerals, and less in areas of voids or deposits of light salts.
The density of rocks inside the Gale crater, where the rover is currently located, was measured as approximately 1,680 kilograms per cubic meter — a surprise for scientists, since past assessments showed that the density of the soil in this area should be much higher — 2,810 kilograms per cubic meter, as determined by the rover’s CheMIn (Chemistry and Mineralogy) instrument.
In 2012, the Curiosity rover landed on the surface of Mars in the Gale crater, tasked with collecting information about the climate and geology of the Red Planet. From the moment of landing, the rover moved towards the foot of Sharpe Mountain, which is the central elevation of the crater, covered with layers of eroded sedimentary rocks.
The rover’s instruments did not include a gravimeter, an instrument used to measure gravitational acceleration, so the scientists came up with a novel approach. Researchers used data from the internal system Rover Inertial Measurement Units, which includes accelerometers and gyroscopes designed to analyse its position in space. However, at rest, the accelerometer can also be used to measure gravitational acceleration. The researchers analysed the data collected between 60 and 1743 salt (day on Mars), gathering about 700 individual measurements. To improve their accuracy, they adjusted the results, taking into account the change in the height at which the rover was located (at higher points, the temperature was lower, and the gravitational acceleration wasn’t as strong), and built a model.
Previously, scientists had assumed that the crater was once completely filled with sedimentary rocks, which eventually formed the top of Sharpe Mountain. Now the data indicates a high porosity of sedimentary rocks along which Curiosity moves, and also that the base of Sharpe Mountain has not been filled with a large amount of soil since its formation — otherwise it would have condensed over time.
The results of the new science study help gain a better understanding of the history of Gale’s crater and the mountain in its center. In addition, the measurements taken by the rover will supplement the data of the gravity surveys, in particular for celestial bodies the atmosphere of which is similar to that of Mars.
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