“The crust is the end-result of everything that happened during a planet’s history, so a lower density could have important implications about Mars’ formation and evolution,” said the lead author, Sander Goossens, of the NASA Goddard Space Flight Center.
The results were found using a gravity map, which is based on satellite-gathered information.
New Method, New Results and a Porous Crust Revealed
Previous attempts at making a gravity map of Mars were unreliable due to the data having a poor resolution. As a result, researchers have, until now, relied more on rock samples to estimate how dense the surface of the Red Planet may be.
These new results take existing gravity maps and run them through a new constraint, which compensates for the fact that data sets cannot notice everything about their object of study. While previous efforts have used what is called the Kaula constraint, this new method creates a constraint which takes into account the changes in elevation on the Martian surface. This, among other things, has the largest-known mountain in the entire solar system, the ten-mile high Olympus Mons.
Based on Martian rock samples, researchers expected Mars’s density to be at least comparable to the surface of Earth’s oceans, about 2,900 kilograms per meter cubed or about 181 pounds per cubic foot.
However, these new results say that it is not as dense. Instead, it has an average crust density of 2,582 kilograms per meter cubed or about 161 pounds per cubic foot, which is more comparable to the Moon.
Fittingly enough, the researchers have actually tested this method on the Moon before applying it to Mars. Using a previous lunar gravity map, they ran this through their new constraint and then compared the results to a more accurate gravity map created by NASA’s Gravity Recovery and Interior Laboratory, or GRAIL. The readings reported were basically the same.
“As this story comes together, we’re coming to the conclusion that it’s not enough just to know the composition of the rocks,” said Greg Neumann, a co-author on the paper. “We also need to know how the rocks have been reworked over time.”
The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport, or InSight mission from NASA is looking to put a new probe on the Red Planet in 2018. Researchers hope it will confirm their theory of Mars’ porous crust.
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