Groundwater on Mars defies expectations: Physics connects seismic data to rock and sediment properties

Groundwater on Mars defies expectations: Physics connects seismic data to rock and sediment properties

Credit: NASA/JPL-Caltech

A new analysis of seismic data from NASA’s Mars InSight mission has revealed a couple of surprises.

The first surprise: The top 300 meters of the subsurface beneath the landing site near the Martian equator contains little or no ice.

“We find that the crust of Mars is weak and porous. The sediments are not well cemented. And there is little or no ice filling the pore spaces,” said geophysicist Vashan Wright of the Institution of Oceanography Scripps from the University of California at San Diego. . Wright and three coauthors published their analysis in Geophysical research letters.

“These findings do not rule out the possibility that there may be ice grains or small balls of ice that are not binding other minerals,” Wright said. “The question is how likely is it that the ice is present in this form?”

The second surprise contradicts a leading idea about what happened to the water on Mars. The red planet may have harbored oceans of water early in its history. Many experts suspected that much of the water became part of the minerals that make up the underground cement.

“If you put water in contact with rocks, you produce a whole new set of minerals, like clay, so the water is not liquid. It’s part of the mineral structure,” said study co-author Michael University of California manga. Berkeley. “There is some cement, but the rocks are not full of cement.”

“Water can also get into minerals that don’t act as cement. But uncemented subsoil eliminates a way to preserve a record of life or biological activity,” Wright said. Cements, by their very nature, hold rocks and sediments together, protecting them from destructive erosion.

The lack of cemented sediments suggests a scarcity of water 300 meters below the InSight landing site near the equator. The average temperature below freezing at the equator of Mars means that conditions would be cold enough to freeze water if it were there.

Many planetary scientists, including Manga, have long suspected that the Martian subsurface would be filled with ice. His suspicions have vanished. Even so, large sheets of ice and frozen ground ice remain at the Martian poles.

“As scientists, we are now faced with the best data, the best observations. And our models predicted that there should still be frozen land at this latitude with aquifers underneath,” said Manga, a professor and professor of UC Earth and Planetary Sciences. Berkeley.

The InSight spacecraft landed on Elysium Planitia, a flat, smooth plain near the Martian equator, in 2018. Its instruments included a seismometer that measures vibrations caused by earthquakes and crashing meteorites.

Scientists can link this information to a large body of knowledge about the surface, including images of Martian landforms and temperature data. Surface data suggest that the subsurface may consist of sedimentary rocks and lava flows. Still, the team had to take into account uncertainties about subsurface properties such as porosity and mineral content.

Seismic waves from earthquakes provide clues about the nature of the materials through which they travel. Potential cementing minerals, such as calcite, clay, kaolinite, and gypsum, affect seismic velocities. Wright’s team at Scripps Oceanography applied rock physics computer modeling to interpret the velocities derived from the InSight data.

“We ran our models 10,000 times each to incorporate the uncertainties into our answers,” said co-author Richard Kilburn, a graduate student working at the Scripps Tectonorock Physics Laboratory, which Wright directs. Simulations showing a subsoil consisting primarily of uncemented material fit the data better.

Scientists want to probe the subsurface because if there is life on Mars, that’s where it would be. There is no liquid water on the surface and life underground would be shielded from radiation. After a sample return mission, a NASA priority for the next decade is the Mars Life Explorer mission concept. The goal is to drill two meters into the high-latitude Martian crust to search for life where ice, rock and atmosphere meet.

The proposed Mars Ice Mapper international robotic mission is already under consideration to help NASA identify potential science targets for the first human missions to Mars. Scripps Oceanography helps prepare young scientists to contribute to these missions.

“My whole life growing up, I’ve heard that the Earth might become uninhabitable,” said study co-author Jhardel Dasent, another graduate student in the lab that Wright leads. “Now I’m at the age where I can contribute to producing the knowledge of another planet that can take us.”

This research was funded by the National Science Foundation, NASA, and the CIFAR Earth 4D program.


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More information:
Vashan Wright et al, A minimally cemented shallow crust beneath InSight, Geophysical research letters (2022). DOI: 10.1029/2022GL099250

Provided by the University of California – San Diego

Subpoena: Groundwater on Mars defies expectations: Physics connects seismic data to rock and sediment properties (2022, 11 August) retrieved 11 August 2022 from https://phys. org/news/2022-08-subsurface-mars-defy-physics -sísmica.html

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