For the first time ever, a NASA lander discovered meteorite impact craters by sensing seismic shock waves created by the space rocks.
Of all the robotic missions to Mars, one of the perhaps most underappreciated ones is the Mars InSight Mission. The lander touched down on Mars in 2018 and has since delivered a plethora of scientific data that has helped scientists better understand what Mars is like on the inside. To date, the robotic mission has recorded over 1,300 “marsquakes,” revealing a side of the red planet previously unknown to science. And although the car-sized lander is expected to power down in 2022 due to a lack of power caused by its solar panels being covered in dust, it continues making history on Mars.
In addition to closely listening to what Mars is like on the inside, the lander’s seismometers detect more than just that; they also pick up the sound of space rocks impacting the surface of Mars. Using data from NASA’s InSight spacecraft, scientists detected four high-speed meteoroid collisions. They then tracked the craters created by these collisions using satellite images from the Mars Reconnaissance Orbiter.
The incoming meteoroids are known as meteors or shooting stars on Earth: and seeing these events is truly a magical moment. When meteoroids reach the thicker atmosphere near the ground, they sometimes explode, causing spectacular airbursts. Some space rocks survive their fiery path through the air and fall to earth as meteorites. As these meteorites make their way to the ground, they travel at such great speeds that when they strike the ground, they leave a huge footprint behind them called an impact crater.
And as you would imagine, Earth is not the only place where this happens. In the 1960s and 1970s, US Apollo missions set up a network of seismic sensors on the moon that detected numerous impacts. There were no natural impacts associated with visual detection of the new crater, however. Artificial impacts were the closest thing to such an observation, for example, the crash-landings of the booster rockets used by Apollo astronauts to leave the moon. Images from orbit and seismic data were used to record these human impacts on the moon. Simulations of seismic waves were conducted using these data.
Both the atmosphere and the ground are affected by incoming meteoroids. Mars has an atmosphere that is equivalent to 1% of Earth’s, but its chemical composition is different. As a result, meteor events on Mars differ from those on Earth. Meteors that strike Mars create a crater that is different from what we would see here on Earth. We find single craters on our planet or on the Moon as well. High-speed space rocks burst into Mars’ atmosphere about half the time, resulting in craters that cluster tightly together. There is a cluster of small impacts formed by these fragments separated at ground level.
Four meteoroid impact events have been observed by InSight recently. The waves travel at different speeds, so we were able to estimate the location of the impacts by comparing their arrival times and other properties. By using satellite imagery from the Mars Reconnaissance Orbiter, these impact locations were confirmed. The size and location of these impact craters allow us to determine how much energy was released by the impact and how fast the incoming space rock was traveling.
The study was published in Nature Geoscience.
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