Mars' crust found to be less dense than previously thought

Researchers often add constraints or adjustments that compensate for the fact that their data cannot include every last detail, to their studies.
By Laurel Kornfeld | Sep 16, 2017
Analysis of a map of Mars' gravity field shows its crust to be more porous and less dense than previously thought, according to a team of scientists at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

The gravity field map comes from data obtained by satellites. While high-resolution gravity maps have been produced for the Earth and Moon, only lower-resolution maps are available for Mars.

The space agency's Gravity Recovery and Interior Laboratory (GRAIL) mission produced the detailed gravity map scientists have of the Moon.

Because scientists are limited to lower-resolution data sets for Mars, determining the density of the planet's crust is a more challenging task for which they have to rely on composition studies of Martian rocks and soils.

In the most recent study, scientists estimate Mars' crust to have a density of 161 pounds per cubic foot or 2,582 kilograms per meter cubed.

That is about the average density of the Moon's crust. Previously, scientists had expected Mars' crust to be at least as dense as that of the crust of Earth's oceans, approximately 181 pounds per cubic foot or 2,900 kilograms per meter cubed.

"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," explained Sander Goossens of the Goddard Space Flight Center, who is lead author of a paper on the findings published in the journal Geophysical Research Letters.

Researchers often add constraints or adjustments that compensate for the fact that their data cannot include every last detail, to their studies.

For this particular project, the research team replaced the standard constraint with a different one based on measurements of varying elevations of features on the Martian surface.

To test the accuracy of their alternative constraint, they applied it to pre-GRAIL gravity field data of the Moon and obtained density results for the lunar crust that match the GRAIL results.

"With this approach, we were able to squeeze out more information about the gravity field from the existing data sets," noted research team member Terence Sabaka, also of Goddard.

Using the new model, the researchers successfully produced accurate maps depicting variations in the Martian crust's density and thickness.

NASA's Interior Exploration using Seismic Investigations, Geodesy and Heat Transport or InSight mission, scheduled for launch in 2018, will land a probe that will delve deep within Mars' interior.

"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 research team member Greg Neumann of Goddard.

"We also need to know how the rocks have been reworked over time."

 

 

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