Surface waves help map Mars interior
Locations of two large meteorite impacts (yellow circles) identified in MRO images. The great circle paths for S1094b R1 (solid) and R2 (dashed) are shown in white, and the R1 path for S1000a is shown in yellow. Background topographic relief is from the Mars Orbiter Laser Altimeter (47). The distribution and sequence of major geological unit groups of Hesperian and Amazonian age (32) are overlaid. Global elevation (orange) and the crust-mantle boundary depth profiles (25) along the R1 and R2 paths (dashed blue) are shown at the top. Credit: Science (2022). DOI: 10.1126/science.abq7157

For the first time, researchers have seen waves on a planet other than Earth. The marsquakes that were caused by two large meteorites that hit Mars were recorded by NASA's InSight landers and analyzed at the University of Maryland.

The team's paper provides new insights into the structure of the Martian crust and brings scientists closer to learning how the planet formed.

This is the first time that seismic waves have been seen on another planet. The study's lead author said that the Apollo missions did not manage it. Kim is an assistant professor in the Department of Geology at the University of Maryland.

After almost three years of detecting only body waves on Mars, the InSight team finally observed surface waves in December of 2016 when two meteorites collided with the red planet. Atypical quake readings led the researchers to suspect the impact sources were near the surface. The images showed that the meteorites had hypocenters on the surface of Mars.

Vedran Lekic, a co-author of the paper, said that prior to this, all our knowledge of the Martian surface was based on what was below the InSight lander. We didn't know if the crust was different on other planets. We were able to get a better understanding of the Mars's crust with the surface waves.

An important clue about how a planet formed and evolved over time can be found in the planet's crust. Earth and Mars are examples of planetary crusts formed through early dynamic processes in the mantle and later modified by other events. A better understanding of the land-shaping conditions of a planet from billions of years ago can be gained through the use of crusts.

The research team analyzed the surface waves that came from the two meteorite impacts to learn more about Mars. They were able to estimate the average properties of the crust 3 to 18.6 miles below the surface of Mars.

The difference between the seismometer and the impact sites on the Martian surface was less than what was seen directly below the landers. The faster speeds suggest that there are differences in the composition of the area.

The density of the material can be determined by the composition of the crust and the number of holes in it. The crust density and composition in that area would have been altered by a volcano. Beneath the impact site, there may be some ice that is less porous and is very different from what we see on the surface.

The team's findings may answer a centuries-old mystery.

"Mars has a unique feature, which is the sharp contrast between the Northern and Southern hemispheres," Lekic said. The southern part has a lot of craters. The northern region is volcanic and has relatively few craters. We were able to learn more about the northern lowlands thanks to the surface waves.

The northern lowlands and southern highlands are believed to be made of different materials. The researchers found that their initial results seem to disprove the idea that the structures are similar at certain depths.

As exploration continues, the team hopes that its research will help researchers find similar mysteries and form better models of Mars.

More information: D. Kim, Surface waves and crustal structure on Mars, Science (2022). DOI: 10.1126/science.abq7157 Journal information: Science