On Dec. 24, 2021, a magnitude 4 marsquake rocked the Red Planet, triggering sensors on NASA's Insight lander. Now, scientists know exactly what shook things up. Before and after images captured by NASA's Mars Reconnaissance Orbiter confirmed it was a meteoroid impact –— the largest on record in the entire solar system.
The impact crater, which measures 492 feet (150 meters) across and 70 feet (21 meters) deep and is located near the Martian equator, now offers scientists a rare peek at subsurface Mars. Moreover, boulder-sized chunks of ice that were dislodged and exposed by the blow represent the lowest-altitude ice ever found on the planet. The details of the impact and the events that followed were described in two studies published in the journal Science on Thursday (Oct. 27).
While larger craters exist on the Red Planet, they were formed long before NASA started scouring Mars 16 years ago, so there are no images or seismic data to explain their origin. This quake and crater represent the largest meteoroid impact ever recorded.
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"The image of the impact was unlike any I had seen before, with the massive crater, the exposed ice, and the dramatic blast zone preserved in the Martian dust," Liliya Posiolova, who leads the Orbital Science and Operations Group at Malin Space Science Systems (MSSS) in San Diego, said in a statement.
MSSS scientists first visualized the crater on Feb. 11, 2022, using two cameras mounted on the Mars Reconnaissance Orbiter. One of the cameras takes daily photos of the entire planet, so the scientists were able to look back through the daily images to find the meteoroid's blast zone. Once they found it, they tied the impact to a 24-hour window and confirmed that the crater formed during the Dec. 24 quake.
According to NASA's Jet Propulsion Laboratory (JPL), the meteoroid was so small –— no more than 39 feet (12 meters) long — that it would have entirely burned up in Earth's atmosphere. Mars' thinner atmosphere, only 1% as dense as Earth's, was less of a deterrent.
Observations of the crater at ground level also revealed new information about Mars' geological makeup, according to the researchers.
"Impact events are extremely helpful in seismology," said Andrea Rajšić, a doctoral candidate at Curtin University in Australia and co-author of the Science paper that detailed the impact. "This is a fantastic way to peek into the interior structure of the Red Planet."
The subsurface ice exposed in the crater and among the ejected debris is closer to the Martian equator than any previously spotted ice specimen on the planet. It could be critical to future missions to Mars, as it hints at a more widespread repository of subsurface ice than was once suspected, the researchers said.
According to JPL, astronauts who will one day visit the Martian surface will need water for drinking, agriculture, and rocket propellant. And now NASA knows that the ice reservoir extends to one of the warmest spots on the planet — hopefully making the work of future astronauts a little easier.
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