Scientists have evidence that a 3-kilometer-high mountain, in the middle of a Mars crater, can be made largely from dust and sand.
To get the information for that surprising conclusion, researchers MacGyvered a navigation tool in NASA's Curiosity rover, and have made it a scientific instrument.
The idea of repurposing Rover's Inertial Measurement Unit came from Kevin Lewis.
"I am amazed that we did not have a surface gravitometer on Mars," says Lewis, a member of the Curiosity Science team and assistant professor of earth science and the planet at Johns Hopkins University.
You can learn a lot about the geology of a planet by measuring subtle changes in its gravity. High density rocks give a signal of gravity stronger than low density rocks.
But to make gravity measurements, it usually has an instrument called Gravimeter.
One day, Lewis began to think of something that appeared regularly in the rover's daily schedule.
"It turns out that every day we do not go with the seller, there is this little rover activity called SAPP-RIMU data activity," says Lewis.
SAPP means "position of surface attitude and pointing". The SAPP-RIMU data activity is something used by engineers to determine the precise orientation of the rover on the surface of the planet.
Within RIMU there are three devices to measure acceleration – similar to accelerometers within a smart phone that measures the movements of the phone.
Kevin Lewis had a kind of epiphany.
"We do not have a gravimeter on the surface of Mars, but we have accelerometers," he says, "and gravity is just an acceleration."
You can not think of gravity that way, but you can do and become scientists.
Thus, with the help of engineers Stephen Peters and Kurt Gonter at the NASA Air Propulsion Laboratory, he could adjust the handling of RIMU data; which gave Lewis his gravimeter.
He knew exactly what he wanted to do with it: trying to figure out how a 15,000-meter-high mountain could form in the middle of Gale's crater, Curiosity Crater arrived.
It's a question that many scientists intrigued.
"There were basically two different schools of thought," says Mackenzie Day, assistant professor at the UCLA Earth and Planetary and Space Science Department.
"Craters are fundamentally great holes in the ground," says Day. "So they are a very good place to accumulate things: accumulate sediments, accumulate dust and sand".
Among the questions that scientists were disconcerting, Day says, is this: it was Gale's crater when it was filled with sediments and then most of that material was eroded, leaving behind what is now called Mount Sharp?
"Or," says Day, "is Mount Sharp something that was developed in the middle of the crater – like a kind of stacking material in the center of the crater – of the winds that slip down the sides of the edge of the crater?"
Could you blow sand and dust then build a 3-mile-high mountain?
Possibly, although he admits that Kevin Lewis runs counter to our expectations.
"They do not usually see that the mountains grow like a lot of straw on Earth," says Lewis.
If the model of the haystack is correct, the rocks at the base of Mount Sharp would not be very dense.
"What we found in this study is that the rocks are surprisingly low density," says Lewis.
Therefore, the theory of the haystack may be right, as he and his colleagues report in the magazine Science.
Lewis says he plans to continue collecting data from his MacGyvered instrument to see if the initial results support.