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bouncing boulders told about frequent marsquakes – Rambler / news


Rolling boulder tracks on Mars point to recent seismic activity

Photo: NASA/JPL-Caltech/ASUNASA/JPL-Caltech/ASU

Martian boulders rolling down the sides of craters and leaving distinctive herringbone patterns could be evidence of recent earthquakes on the planet, according to Indian scientists who have studied many of these footprints captured by the HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter.

Indian scientists have discovered thousands of tracks left by falling and rolling boulders in the form of chains of marks on Mars and have shown that most of them disappear within a few years. Such traces can be used to pinpoint recent seismic activity on the planet and show that Mars is still a living dynamic world where many geological processes have not yet ended. An article about this was published in the journal Geophysical Research Letters.

Similar rockfalls have also been seen elsewhere in the solar system, including on the Moon and even on comets. However, a significant difference lies in the time when these rockfalls occurred – if they happened on already dead celestial bodies in the distant past, then on Mars all this is happening at the present time.

To reach this conclusion, Dr. Vijayan, a planetary scientist at the Physical Research Laboratory in the Indian city of Ahmedabad, and his colleagues studied thousands of images of Mars’ equatorial region. The photographs were taken between 2006 and 2020 by the HiRISE high-resolution camera aboard NASA’s Mars Reconnaissance Orbiter, which captures 30cm-per-pixel images from 300km above the surface of Mars. “We can distinguish individual boulders this way,” explains Dr. Vijayan.

The scientific team manually looked through many images and looked for characteristic chain elements – signs of falling stones on the sides of impact craters. They usually leave a distinctive herringbone pattern. Dr. Vijayan and his team found more than 4,500 of these boulder tracks, the longest of which stretched over two kilometers. Their total length is about 900 km. According to Dr. Vijayan, sometimes the tracks change direction, sometimes they suddenly fork. Such changes probably indicate that the boulder broke into pieces, and its fragments continued to roll down the slope.

At the same time, about a third of the traces studied by the researchers were absent from earlier images, which means that they must have formed after 2006.

More recent traces are framed by placers of Martian regolith. Indian researchers believe that these formations, which Dr. Vijayan and his colleagues called “boulder ejections”, are ejected from the ground every time a boulder hits the surface.

Tracking the same footprints across images over time, the team found that the ejecta from the boulders typically only remain visible for about four to eight years. The researchers concluded that the winds that continuously sweep over the surface of Mars pour dust and sand and erase traces. Some of these tracks disappear in as little as two to four Martian years, while others can persist for more than six Martian years, suggesting varying degrees of weathering. On Earth, such wind erosion proceeds even more intensively.

Scientists have noticed that relatively quickly disappearing boulder emissions make it possible to track the places where the boulders have shifted more recently. And since seismic activity is a common cause of rockfalls on Earth, we must assume that something similar is happening on Mars. Vijayan and his collaborators calculated that approximately 30% of the boulder tracks found were concentrated in the Cerberus Fossae depression on Mars. Researchers consider this circumstance a pronounced anomaly, since this entire region covers only 1% of the studied area.

“There are a lot of boulders in the surrounding craters,” says Dr. Vijayan. “Some of them even have multiple falls in the same place.”

New evidence of Mars’ geologic activity contradicts conventional wisdom that it’s all in the past, said Ingrid Daubar, an American planetary scientist at Brown University in Providence, who was not involved in the study but commented on it for The New York Times. “For a long time we thought Mars was a cold, dead planet,” she says.

Alfred McEwan, an American planetary scientist at the University of Arizona and chief scientist on the HiRISE camera, agrees that the geology of Cerberus Fossae, located in the Tarshish volcanic region, may be prone to seismic activity. “These gigantic masses of dense rock extruded to the surface create stresses in the entire surrounding Martian crust,” says Dr. McEwan.

Since 2019, the NASA InSight lander, which specializes in studying the internal structure and composition of Mars and is equipped with a seismograph, has in turn recorded hundreds of marsquakes, with two of the largest of them occurring last year in the region described.

In the future, Dr. Vijayan and his collaborators plan to extend their research to the subpolar regions of Mars as well. At the same time, all planetary scientists hope that the HiRISE camera will not let them down and continue its work, despite the fact that the design life of the tool has long expired.

Traces from boulders rolling down the slopes are also recorded by the CaSSIS camera of the European-Russian ExoMars Trace Gas Orbiter, as previously reported by the European Space Agency. These images show part of the Labyrinth of Night canyon system. The entire set of plateaus and canyons that make up this system stretches for 1200 km, and individual rocks reach a height of 5 km. At maximum magnification, several boulders were observed falling off the edge of the cliff and leaving small indentations in the soft ground as they rolled down the slope. The Trace Gas Orbiter arrived in orbit in 2016, and its main task is to search for traces of life in the present or past of Mars.

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