WASHINGTON – Seismic waves generated by a meteorite impact on the other side of Mars, where NASA’s InSight lander is located, have provided new clues about the interior of the Red Planet, prompting scientists to reassess the anatomy of Earth’s neighboring planet.
New seismic data suggests an unknown layer of molten rock surrounding a molten metallic core – the planet’s innermost component – that is smaller and denser than previously thought, researchers said Wednesday.
Waves produced by earthquakes – including those caused by meteorite impacts – vary in speed and shape as they pass through different materials within a planet. Data from InSight’s seismometer instrument allows the planet’s internal structure to come into focus.
The meteorite impact that occurred in a highland area of Mars called Tempe Terra on September 18 2021 triggered an earthquake measuring 4.2 on the Richter scale and left a crater about 425 feet (130 meters) wide. It takes place on the opposite side of Mars from InSight’s location in a plain region called Elysium Planitia.
“The importance of distant side impacts is that they produce seismic waves that travel through the interior of the planet, including the planet’s core. Previously, we had not observed any seismic waves passing through the core. We only see the reflection from above. essentially,” said planetary scientist Amir Khan of ETH Zürich in Switzerland, lead author of one of two scientific papers on the new findings published in the journal Nature.
The wave behavior suggests that previous assessments of Mars’ interior were missing, namely the existence of a layer of liquid silicate about 90 miles (150 km) thick surrounding the core. This liquid region is at the bottom of the planet’s interior called the mantle.
The researchers also recalculated the size of the core and found that it has a diameter of about 2,080 miles (3,350 km), with a volume about 30% smaller than previously thought.
Researchers say the mantle – a rocky layer sandwiched between the crust and the planet’s outer core – stretches about 1,055 miles (1,700 km) below the surface. Unlike Mars, Earth does not have a liquid layer around its core. One of the two studies published on Wednesday showed that this layer had melted completely, while the other showed that most of it had melted completely, and the top part had melted partially.
“The liquid and partially liquid layer is basically composed of silicates (rock-forming minerals) enriched with iron and radioactive heat-generating elements compared to the solid mantle above it,” said Henri Samuel, a planetary scientist from the French national research. CNRS organization working at the Institut de Physique du Globe de Paris and lead author of the second study.
Mars’ core consists mostly of iron and nickel, but also has some lighter elements such as sulfur, oxygen, carbon and hydrogen. The researchers concluded that these lighter elements make up about 9-15% of the core composition, lower than previous estimates.
“The amount of light elements is no different from the Earth’s core, which is estimated to be around 10%,” said Khan.
Mars, the fourth planet from the sun, has a diameter of about 4,220 miles (6,791 km), compared to Earth’s diameter of about 7,926 miles (12,755 km). The total volume of the earth is almost seven times larger.
NASA is retiring InSight in 2022 after four years of operation.
“We have learned a lot about Mars by studying the unique seismic records provided by the InSight mission,” said Samuel. “Planet is a rich and complex system because it is a place where different types of processes coexist and act at different spatial and temporal scales, and Mars is no exception.”
2023-10-27 19:30:00
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