Surface waves help map the interior of Mars

تساعد الموجات السطحية على رسم خريطة للمريخ الداخلية

Large meteor impact sites (yellow circles) identified in the MRO images. The great-circle pathways of S1094b R1 (solid) and R2 (dashed) are shown in white, and the R1 pathway of S1000a is shown in yellow. Background topographic relief from the Mars orbital laser altimeter (47). The distribution and sequence of major geological unit groups of the Hesperian and Amazonian epochs have been superimposed (32). The global elevation (orange) and depth profiles of the crustal boundaries (25) along the R1 and R2 tracks (dashed blue) are shown at the top. attributed to him: Sciences (2022). DOI: 10.1126 / science.abq7157

Researchers have observed for the first time that seismic waves propagate on the surface of a planet other than Earth. The earthquakes triggered by two large meteorites that struck Mars were recorded by NASA’s InSight rover and analyzed at ETH Zurich in collaboration with the InSight Science team, which includes researchers from the University of Maryland.

Published in the magazine Sciences On October 27, 2022, the team’s paper provided new insights into the structure of Mars Shellbringing scientists closer to learning how the planet formed and evolved over time.

“This is the first seismic time surface waves It was observed on a planet other than Earth. said lead author of the study, Doyeon Kim. “Kim is currently a visiting assistant professor in the UMD Department of Geology and a senior assistant at the ETH Institute of Geophysics,” said the study’s lead author, Doyeon Kim.

Nearly three years after detecting only body waves (seismic waves traveling through a planet’s body) on Mars, the InSight team finally noticed surface waves (seismic waves traveling along a planet’s surface) in late December 2021, when a meteorite collided with the Red Planet. The atypical earthquake readings led the researchers to suspect that the sources of the impact were near the surface, so they compared the data with information from the Mars Reconnaissance Orbiter. Images taken by the orbiter confirmed that both meteorites had epicenters (the point of origin) on the surface of Mars.

“Before that, all our knowledge about Mars’ crust was based on what was below the InSight rover,” said UMD Associate Professor of Geology Vedran Lekic, a co-author on the research paper. “But Mars is a big planet – we didn’t know if the crust was any different at other locations across the planet. With these surface waves, we were finally able to get a better understanding of the crust along a large stretch of Mars.”

The planet’s crust, or hard outer shell, provides important clues about how the planet formed and evolved over time. Most planetary crusts, including those of Earth and Mars, were formed by dynamic early processes in the mantle and were later modified by other events such as volcanism, deposition, erosion, and impact craters. As a result, the crusts could allow researchers to gain a better understanding of Earth-forming conditions for the planet billions of years ago.

To learn more about the Martian crust, the research team analyzed the speed of surface waves coming from the meteor impact. This allowed them to exploit the relationship between surface wave velocity, frequency, and depth to estimate average crustal properties from 3 to 18.6 miles below the surface of Mars.

On average, the Martian crust between the InSight seismometer and the two meteor impact sites did not differ strongly with depth and had a faster seismic velocity than previously observed just below the rover. Faster velocities indicate either compositional differences or lower porosity in the areas traversed by the surface waves.

“The composition of the crust will determine some of the density, but also factors like porosity; if you have a lot of holes in the crust, it can also reduce the density of the material,” explained Nicholas Schmerr, assistant professor of geology at UMD. , another co-author of the paper. “The volcano, with all its intrusions and magma rising through the crust beneath it, could also have changed the crust’s density and composition in that region. As we look north on Mars, there’s likely to be some subsurface ice in the crust under the influence, which is less porous. It is completely different from what we see under the InSight lander.”

The team’s findings may also provide answers to a centuries-old puzzle: the cortical division of Mars.

“Mars has a very unique feature, which is the sharp contrast between the northern and southern hemispheres,” Lekic noted. “The southern part is really old, with high terrain and heavily cratered. Meanwhile, the northern area is volcanic, very low and with relatively few craters. The surface waves we detected helped us learn more about the northern lowlands, which we could only speculate before “.

One popular theory behind this is that crusts in the northern lowlands and southern highlands are composed of different materials. However, the researchers found that their initial findings seemed to refute that notion, even suggesting that crustal structures might be surprisingly similar at certain depths.

The team hopes its research will continue to help researchers investigate similar mysteries and form better models of Mars as exploration continues.

Two major meteorite collisions shed light on the interior of Mars

more information:
Kim, Surface waves and crustal structure on Mars, Sciences (2022). DOI: 10.1126 / science.abq7157

Introduction of
University of Maryland

the quote: Surface waves help map the interior of Mars (2022, Oct 27) Retrieved Oct 28, 2022 from

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