NASA spacecraft detect biggest meteor strikes on Mars

Two NASA spacecraft at Mars — one on the surface and the other in orbit — have recorded the biggest meteor strikes and impact craters yet.

The high-speed barrages last year sent seismic waves rippling thousands of miles across Mars, the first ever detected near the surface of another planet, and carved out craters nearly 500 feet across, scientists reported on Thursday in the journal Science.

On December 24, 2021, a meteorite hit Mars' surface, triggering magnitude 4 tremors, which were detected by NASA's InSight spacecraft — which landed on the planet four years ago — 3,500 kilometres away, they reported.

The true origin of this so-called marsquake was only confirmed when the Mars Reconnaissance Orbiter (MRO) was able to take a picture of the newly formed crater created by the hit when it flew over the impact site less than 24 hours later.

The image is impressive, showing blocks of ice that were spewed up onto the planet's surface around150-metre wide and 21-metre deep hole.

The crater is the largest ever observed since the MRO began its Mars orbit 16 years ago.

And though meteorite impacts on Mars are not rare, "we never thought we'd see anything that big," Ingrid Daubar, who works on the InSight and MRO missions, told reporters at a press conference on Thursday.

Researchers estimate that the meteorite itself would have measured between 4.8 to 12 metres across.

An object of that size would have disintegrated in Earth's atmosphere before falling to the ground here.

"It is simply the biggest meteorite impact on the ground that we have heard since science has been done with seismographs or seismometers," said planetology professor Philippe Lognonne, who participated in two studies related to the observation published in the journal Science on Thursday.

NASA released an audio recording of the collision, which was made by speeding up the vibrations collected by the seismometer.

'Useful' ice presence

The valuable information gathered in studying the crash will contribute to a deeper knowledge of Mars' interior and the history of how the planet was created, scientists said.

The presence of ice, in particular, is "surprising," said Daubar, who also co-authored the two studies.

"This is the warmest spot on Mars, the closest to the equator, we've ever seen water ice," she said.

In addition to the information, this discovery offers about the Martian climate, the presence of water at this latitude — and not just near the poles — could prove "really useful" for future human visitors to Mars, director of NASA's Planetary Science Division Lori Glaze said.

"We'd want to land the astronauts as near to the equator as possible," she said, to take advantage of warmer temperatures.

"That ice could be converted into water, oxygen or hydrogen," Glaze said.

Probe worked 'marvellously'

The impact was powerful enough to generate seismic waves both down to the planet's core and across its crust horizontally, making it possible to study Mars' internal structure — revealing that the crust on which InSight sits is less dense than the crust the waves travelled over from the crater site.

The end of InSight's mission — which recorded more than 1,300 marsquakes in total — could come in the next couple of months, according to Bruce Banerdt of NASA's Jet Propulsion Lab, due to the expected accumulation of dust on the lander's solar power panel.

It's "sad," he said while celebrating that the probe worked "marvellously" for four years.