It wasn't the average marsquake that the Insight Mars lander heard rip-roaring through the red planet's ground last Christmas Eve.
NASA's Mars Reconnaissance Orbiter apparently found the source of the rumble a couple of months later from its vantage point in space: a spectacular meteor strike over 2,000 miles away near Mars' equator, estimated to be one of the largest impacts observed on the neighboring planet.
But what's thrilled scientists perhaps as much as or more than the recorded seismic activity is what the meteor uncovered when it slammed into Mars — huge, boulder-size chunks of ice blasted out of the crater. Up until now, underground ice hadn't been found in this region, the warmest part of the planet.
"This is really an exciting result," said Lori Glaze, NASA's director of planetary science, during a news conference Thursday. "We know, of course, that there's water ice near the poles on Mars. But in planning for future human exploration of Mars, we'd want to land the astronauts as near to the equator as possible, and having access to ice at these lower latitudes, that ice can be converted into water, oxygen, or hydrogen. That could be really useful."
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The discovery, recently published in two related studies in the journal Science, is something of a grand finale for NASA's Insight lander, which is losing power rapidly. Scientists have estimated they have about four to eight weeks remaining before they lose contact with the lander. At that point, the mission will end.
For the past four years, Insight has studied upward of 1,000 marsquakes and collected daily weather reports. It has detected the planet's large liquid core and helped map Mars' inner geology.
Program leaders have prepared the public for this outcome for some time. While the spacecraft has sat on the surface of Mars, dust has accumulated on its solar panels. The layers of grit from the red desert planet have blocked out the rays it needs to convert into power. The team has cut back on Insight's operations to squeeze out as much science as possible before the hardware goes kaput.
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Then, the team got a bit more bad news last month. A brutal dust storm swept over a large portion of Mar's southern hemisphere. Insight went from having about 400 watt-hours per Martian day to less than 300.
"Unfortunately, since this is such a large dust storm, it's actually put a lot of dust up into the atmosphere, and it has cut down the amount of sunlight reaching the solar panels by quite a bit," said Bruce Banerdt, Insight's principal investigator at NASA’s Jet Propulsion Laboratory in Southern California.
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But NASA believes scientists will continue to learn a lot about the past climate conditions on Mars and when and how ice was buried there from the fresh crater, which spans 500 feet wide and just shy of 70 feet deep.
They are confident the ice came from Mars and not the meteor, said Ingrid Daubar, a planetary scientist at Brown University who leads InSight’s impact science working group.
"An impact of this size would actually destroy the meteorite that came in to hit the surface," she said. "We wouldn't expect much, if any, of the original impactor to survive this high energy explosion."
