InSight ‘hears’ its first meteor impacts on Mars

Sep. 19 () –

The Mars lander’s seismometer has detected vibrations from four separate impacts in the last two years, as NASA has now announced.

InSight detected seismic waves from four space rocks that crashed into Mars in 2020 and 2021. These not only represent the first impacts detected by the spacecraft’s seismometer since InSight touched down on the Red Planet in 2018, but it also marks the first time seismic and acoustic waves have been detected from an impact on Mars.

A new article published this Monday in Nature Geoscience details the impacts, which ranged from 85 to 290 kilometers from InSight’s location, a region of Mars called Elysium Planitia.

The first of four confirmed meteorites, the term used for space rocks before they hit the ground, made the most spectacular entrance: It entered the atmosphere of Mars on September 5, 2021, and exploded into at least three fragments, each of which left a crater.

NASA’s Mars Reconnaissance Orbiter then flew over the estimated impact site to confirm the location. The orbiter used its black-and-white context camera to reveal three dark spots on the surface. After locating these spots, the orbiter team used the High Resolution Imaging Science Experiment, or HiRISE, camera to get a color close-up of the craters (the meteoroid could have left additional craters on the surface, but they would be too small to see in HiRISE images).

“After three years of InSight waiting to detect an impact, those craters looked beautiful,” he said. it’s a statement Ingrid Daubar of Brown University, a co-author on the paper and a Mars impact specialist.

After analyzing earlier data, scientists confirmed that three other impacts had occurred on May 27, 2020; February 18, 2021; and August 31, 2021.

Researchers have wondered why they haven’t detected more meteorite impacts on Mars. The Red Planet is adjacent to the solar system’s main asteroid belt, which provides an ample supply of space rocks to mark the planet’s surface. Because Mars’ atmosphere is only 1% thicker than Earth’s, more meteoroids pass through it without disintegrating.

InSight’s seismometer has detected more than 1,300 earthquakes. Provided by France’s space agency, the National Center for Space Studies, the instrument is so sensitive that it can detect seismic waves thousands of kilometers away. But the event of September 5, 2021 marks the first time an impact has been confirmed as the cause of such waves.

The InSight team suspects that other impacts may have been obscured by wind noise or seasonal changes in the atmosphere. But now that the distinctive seismic signature of an impact on Mars has been discovered, scientists hope to find more hiding within nearly four years of InSight data.

The seismic data offers several clues that will help researchers better understand the Red Planet. Most earthquakes are caused by underground rocks cracking from the heat and pressure. Studying how the resulting seismic waves change as they move through different materials gives scientists a way to study the crust, mantle, and core of Mars.

The four confirmed meteor strikes so far have all produced small earthquakes with a magnitude of no more than 2.0. Those smaller earthquakes give scientists only a glimpse of the Martian crust, while seismic signals from larger earthquakes, such as the magnitude 5 event that occurred in May 2022, they can also reveal details about the planet’s mantle and core.

But the impacts will be critical in refining the Mars timeline. “Impacts are the clocks of the solar system,” said the paper’s lead author, Raphael Garcia, of the Institut Supérieur de l’Aéronautique et de l’Espace in Toulouse, France. “We need to know the impact rate today to estimate the age of different surfaces.”

Scientists can approximate the age of a planet’s surface by counting its impact craters: the more they see, the older the surface. By calibrating their statistical models based on how often they see hits now, scientists can estimate how many more impacts occurred earlier in the solar system’s history.

InSight data, combined with orbital imagery, can be used to reconstruct a meteoroid’s trajectory and the size of its shock wave. Each meteoroid creates a shock wave when it hits the atmosphere and an explosion when it hits the ground. These events send sound waves through the atmosphere. The larger the explosion, the more this sound wave tilts the ground when it reaches InSight. The lander’s seismometer is sensitive enough to measure how much the ground tilts in such an event and in what direction..

“We are learning more about the impact process itself,” Garcia said. “Now we can match different crater sizes to specific seismic and acoustic waves.”

The lander still has time to study Mars. Dust buildup on the lander’s solar panels is reducing their power and will eventually cause the spacecraft to shut down. Accurately predicting when is difficult, but based on the latest power readings, engineers now believe the lander could shut down between October of this year and January.