Two meteorites rock Mars, allowing first study of extraterrestrial seismic waves

Although it bears the name of the god of war, for the past three decades—much to the despair of star seismologists—Mars has been fairly peaceful. These experts were content to measure the vibrations of small meteorites and gentle showers of hundreds of small meteorites. marsquares, Generally 4 magnitudes coming from the inner layers of the planet. Like someone trying to peer into a dark room by the light of a match, researchers have only had scant data since 2019 offered by a single seismograph, NASA’s InSight probe. But peace of mars It ended abruptly at the end of 2021. Okay, two strikes. Two large meteorites hit the crust and finally allowed the detection of surface seismic waves. This is the first time they have observed a planet other than Earth. The result of these two is excellent Mark Squares Presented in two articles New issue of the magazine science, Posted this Thursday.

“Until now, our knowledge of the Martian crust has been based on single-point measurements by the InSight module,” Doyon Kim, a scientist at the Federal Polytechnic School of Zurich, Switzerland, explains in a press release. Analysis of surface waves caused by meteorites offers important clues that allow mapping of crustal and upper mantle structures. It’s as if two powerful spotlights illuminate the room, which until now was lit only by a match.

Mars inside

The new data show that Mars has a layered structure similar to Earth, with a core about 1,830 kilometers in radius (half that of Earth), a mantle 1,500 kilometers thick, and a crust between 20 and 70 kilometers. about 33 kilometers of land). This crust is the result of dynamic mantle processes and subsequent magmatic processes. Studying these layers, experts say, sheds light on the conditions of the planet billions of years ago. On Mars, however, there are no tectonic plates, so seismic processes are not similar to those on Earth.

There are two types of seismic waves, internal or body waves – those that originate from inside the planet – and surface waves – those that originate in the crust. Capturing these two types of waveforms makes it possible to cross their data and scan Interior of a three-dimensional planet. The more intense and prolonged the waves, the deeper they are will bend down Star seismologists.

The force generated by the meteor impact in 2021 was relatively weak, and the waves they caused lasted for 8 to 15 seconds, so Kim and his colleagues were able to map a depth of about 30 kilometers. The propagation speed of these waves was not uniform, indicating changes in crustal density.

It is important to know the composition of Mars’ core in order to know if there was a protective shield in the past that could have made the planet habitable.

“The presented seismic model offers a more sophisticated way to understand the structures of the Martian crust; Some structures that should be considered in future topographic and gravity analyses,” independent seismologists Yingjie Yang and Xiaofei Chen note in a commentary on the article.

The Mysterious “Mars Dichotomy”

Mars has something similar two face And the new research could also help unravel what has been a mystery for centuries: the stark contrast between the southern and northern hemispheres. The southern plateau is covered with meteor craters; The north consists of flat, volcanic plains that may have been covered by oceans early in the planet’s history. This division between the southern highlands and the northern plains is what is known as the Martian dichotomy, experts say.

“We don’t yet have a commonly accepted explanation for the dichotomy because we’ve never been able to see the deep structure of the planet. But now we’re starting to find out,” says Domenico Giardini, professor of seismology and geodynamics at the Polytechnic of Zurich. The first results seem to disprove one of the most common theories about the Martian dichotomy: the northern and southern crusts are probably not made of different materials, as has often been assumed, and their structure may be remarkably similar at great depth.

Why Mars has these two faces is still a matter of debate, Yang and Chen note. There are those who believe that there was a violent impact in the southern hemisphere, which explains the unevenness of the terrain; while others advocate internal mantle processes to explain these features. “A more granular understanding of the structures of the deep crust and upper mantle will help distinguish competing hypotheses for the geodynamic evolution of Mars,” they add.

Experts say that in principle the only seismograph on Mars will stop working in December. Martian dust accumulating on its solar panels will drain it of power. However, there is still a lot of data to analyze and, in addition, two future missions (European ExoMars, in difficulties due to the war in Ukraine) and China’s Tianwen should bring a more advanced seismograph to our neighbor.

Source: El Diario





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