Scientists working with the Curiosity rover used part of their navigation equipment, an accelerometer like their phone, to make an important measurement about the mysterious geology of Mars.
Curiosity is currently touring Mount Sharp, a 5-kilometer-high mountain (3 miles) in the center of Gale Crater. But it is not clear if the mountain is the result of the crater filling and the loss of material due to erosion, or if the mountain looks more like a large dune of deposited material. Curiosity does not have a scientific instrument to determine the nature of the mountain, but it has a navigation equipment that measures strength. So the scientists became creative.
"I realized that you can download an application on your phone and, not very accurately, but you can measure [the force of Earth’s gravity] Because your phone has accelerometers, "study lead author Kevin Lewis, an badistant professor at Johns Hopkins University, told Gizmodo, he thought he could do the same with Curiosity's accelerometers and perform some interesting science.
Gravimetry, or the accurate measurement of changes in the local gravitational field, is a useful way to understand rocks below the surface, since the gravity of an object increases with its mbad. Apollo 17 had a gravimetry experiment to study the Moon, for example, but Curiosity does not have a gravimeter. However, it has a navigation system that includes gyroscopes and an accelerometer to measure changes in speed, acceleration and orientation.
The navigation system is not as sensitive as a gravimeter would be, but the scientists did. They acquired the data on the accelerations experienced by the mobile, then adjusted it to take into account aspects such as the location of Curiosity on Mars, as well as the potential effects of temperature and elevation on the equipment.
Their badysis revealed a surprise: the average density of rocks below Curiosity was lower than expected. This implied that the dirt was much more porous, which means that it had more holes, than scientists expected. In addition, they could infer that the sediments would not be very deep, since otherwise they would be more compact or filled.
All these points together seem to imply that Mount Sharp was not the result of erosion that created a high peak, but was formed through the sediment that blows into the already formed crater, resulting in a huge deposit, according to the document. published today in Science.
"My first impression was that it is an ingenious engineering trick to use instruments aboard the rover that were not designed as scientific instruments to do science," said Gizmodo Kirsten Siebach, a Martian geologist and an badistant professor at Rice University. He noted that the porosity value of the rocks was surprisingly high. She said the work seemed to confirm some previous observations of Gale Crater, but contradicts others.
"This pushes us to better understand how low-porosity rocks on Mars behave," he said.
Measurements like these come with inherent limitations, such as the introduction of potential biases when trying to choose what data to use and uncertainties when using an instrument for a task for which it was not designed.
But this is science, and the document reveals new information that brings us closer to knowing what is really happening inside the crater, and must be considered along with other experiments, simulations and data. And there are more experiments to build the body of evidence: Mars InSight will be able to tell scientists about the geology of the planet in general, based on how heat flows through the planet, while Mars 2020 will have a ground penetration radar for collect information from the subsoil. in its place of landing, Jezero crater.
It is not the first time we hear about scientists reusing navigation equipment to do science, but this is particularly ingenious.
Lewis said: "One of the things I really love about this study is that it's my kind of science: finding new ways to use existing data and MacGyvering is a new scientific instrument."