A Remote Curiosity Rover Hack Helps to Unravel a Martian Mystery

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The Mars Curiosity rover of NASA — A self-portrait taken by the Mars Curiosity rover of NASA

While a Martian rover, Opportunity, has passed away, his youngest cousin, Curiosity, has solved a mystery. He measured tiny changes in the severity of the red planet, allowing his mission team to return home to NASA to understand how a huge 5-kilometer high mountain, explored by the rover, had formed.

The answer to this question may seem unimportant: it was probably formed when sand and wind-blown sediments settled higher and higher. But what's more intriguing is how the rover actually measured the tiny changes of gravity that gravitate across the mountain to get that answer – while none of his scientific instruments were designed to measure anything it's like that.

Curiosity came to Mars on August 5, 2012, landing in Gale Crater and began digging – to see if our nearest planetary neighbor is, or could have ever been, the focus of microbial life.

"Curiosity has been conceived more as a surface geology mission than as an underground geophysical mission," says Kevin Lewis, an assistant professor of Earth and Planet Sciences at Johns Hopkins University and a member of the United States. Curiosity mission team. He is also the lead author of the gravity study, published in Science. The rover has never been designed to deeply scan the rusty rocks under his wheels, he adds.

As part of its mission, Curiosity climbed Aeolis Mons – unofficially known as Mount Sharp, according to a renowned Martian researcher – since 2014. The sedimentary rocks of Mars, including those dating back to the early 20th century, have been known to the world. Aeolis Mons, contain detailed information about the climate of the planet, much like they do on Earth.

Unlike Mars, however, the Earth has active plate tectonics. With its ability to tear plates and consume others in subduction zones, much of the Earth's sedimentary history is annihilated. The same processes do not happen on Mars. This makes Aeolis Mons an extremely ancient record of the long-lost environment of Mars, unlike anything in our world. "It's an unparalleled story book," says Lewis, just waiting to be explored.

Understanding how he formed has occupied the minds of many geoscientists and has sparked much debate. For some time now, two major hypotheses have been discordant. One of the ideas was that it was a mountain that had been built from the base of the crater of Gale thanks to the dust raised by the wind that remained in place; another was that it was once buried under sediments that then eroded, leaving the mountain alone.

One solution is to look at its internal structure, but it does not seem that Curiosity is able to do it. A gravimeter, an instrument that takes into account small variations in the local gravity field to determine the distribution of mass, would have been perfect. However, as Curiosity Geospatial Information Specialist Fred Calef explained, such a tool "should not have been considered a vital tool for the mission" at the time of the calls.

Curiosity is also equipped with accelerometers. As in smartphones, they measure movement changes and allow the rover to know how fast he is moving and where he is heading.

Gravity causes the acceleration of the mass, which allows the accelerometers to also measure the gravitational variations. "You can download a phone application that can measure gravity," says Lewis. "Not enough to do science for the most part," but it will still give you a reading.

Lewis thought exactly of that one day and had a moment of light bulb. Why not apply the same logic to Curiosity accelerometers? Seriously, one of Lewis's colleagues had already tinkered with the software of these instruments on the distant rover. For some time he had been using it to detect changes in the orientation of the small boat when it was not moving, as had been created by changes in the surrounding environment.

After other calibration cycles, Curiosity was prepared to detect gravitational fluctuations at shutdown. Climbing higher and higher, the gravitational signal of the mountain became more and more distinct and the complexity of its structure became evident.

Gravimeters on Earth are up to a thousand times more accurate than modified Curiosity accelerometers, but they were still good enough to reveal that Aeolis Mons was full of tiny holes, just like a slice of Swiss cheese, and had a relatively low density. . This indicates that it has never been buried significantly by sediment, which could have eliminated these holes.

This discovery is consistent with previous work, says Lewis, when the Curiosity exercise easily pierced sediment on its slopes, alluding to a weak, perhaps porous structure. Until now, with all the data taken into account, it seems that the lower part of the mountain consisted of layers deposited in a humid lacustrine environment within the crater Gale. Then, after a climatic transition, everything dried up and the mountain continued to rise as the sediments carried by the wind came into flight.

Despite the lack of appropriate tools, Calef says this study shows how ingenious the rover scientists are in "extracting new scientific data from all possible sources".

The rover is always climbing higher, collecting more data and refining its gravity hooks, so that the structure of the mountain will be more clearly defined.

Starting to solve the mystery of Aeolis Mons is exciting, but the fact that Curiosity can do it through hacking at 34 million kilometers seems like a remarkable feat. "It's one of the most fun studies I've ever done as a scientist," says Lewis.

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