Dying NASA spacecraft records epic ‘Mars quakes’

The first and only spacecraft to study earthquakes on Mars is about to die. A recent Martian storm covered the solar panels of NASA’s InSight lander with dust, blocking out much of the sunlight it needs to charge its batteries. Mission controllers now run its seismometer periodically to conserve power. In weeks, the spacecraft will likely stop responding to commands from Earth and sink into oblivion.

But InSight didn’t go out without a bang. On October 27, scientists announced that last year the mission detected seismic waves created by the largest meteorite impacts ever seen on Mars. Both meteorites hit the planet with the energy of a small nuclear bomb. By tracking the massive seismicity passing through Mars, scientists were able to study the properties of the red planet’s crust thousands of kilometers away from InSight and solve a mystery about whether the spacecraft happened to be in a geologically unusual place.

The findings add to InSight’s rich legacy of discoveries. From arrival at Mars in November 2018, he has collected information on more than 1,300 “Marsquakes.” This allowed the researchers to calculate, among other things, the long-sought after size of the core of Mars and on the thickness of its crust. Just last month, researchers used data from five earthquakes to determine that Mars’ mantle is richer in iron than Earth’s. All this information about Mars’ interior will help scientists understand how the planet formed and evolved over billions of years.

“Before the mission, I was always showing all these cartoons of planets cut in half,” said Mark Panning, InSight’s project scientist at the Jet Propulsion Laboratory (JPL) in Pasadena, California. “Now the cartoon has gone from question marks and fuzzy boundaries to a real picture of what the interior of Mars is like. It was what we promised and we delivered.”

Seismic discoveries

It was not always clear that scientists would succeed. In 2012, NASA decided to build and launch the $994 million InSight, a controversial choice since the agency had several other Mars missions already in the queue. Then problems building his supersensitive seismometer forced a $150 million, two-year launch delay. After InSight finally arrived on Mars, a German instrument nicknamed the Mole that was supposed to measure heat flow in the soil failed because it couldn’t sink into the ground. The mission didn’t even touch your first marcus up to five months after landing—and when it finally did, researchers struggled to interpret what they were seeing.

“In the beginning, we weren’t really sure how much we could get out of the data,” says Brigitte Knapmeier-Erdrun, a planetary scientist at the University of Cologne in Germany.

But things improved for InSight in its second Martian year. The spacecraft is located near the Martian equator, in a region known as Elysium Planitia. Many of the earthquakes it detects come from a geologically active region known as Cerberus Fossae, about 1,500 kilometers away, where underground injections of magma are thought to cause tremors. In August and September 2021, the spacecraft first detected tremors on the far side of the planet.

And on May 4 of this year, InSight detected a 4.7-magnitude quake—the largest ever (most of InSight’s detections are in the 2 to 3 magnitude range). On Earth, such an earthquake can be felt by people if they are close to the epicenter.

“It’s a beautiful gift from Mars,” said Philippe Lognone, a geophysicist at the Paris Institute of Earth Physics who led the seismometer team.

The researchers have not yet published what they learned from the “big one.” But it was so big that it sent seismic energy through the surface layers of the Martian crust, creating what’s known as a surface wave — which can reveal more information about the planet’s interior than other types of seismic waves. “I don’t want to tip us too much,” says Bruce Bannerd, a geophysicist at JPL and InSight’s principal investigator. “But it does provide information across the entire spectrum, from the shallow crust to the deepest mantle and core.”

Deep impacts

Meanwhile, scientists have analyzed the surface waves generated during the meteorite’s two record-breaking impacts last year, on September 18 and December 24. InSight picked them up from thousands of kilometers away.

They rippled through the Martian crust north of InSight, which is near a key geological boundary where the terrain is smoother and lower in elevation than the heavily cratered southern mountains. The way surface waves travel through the crust to the north suggests it is denser than the crust beneath Insight, which landed in a region where the rocks are particularly porous.

InSight was able to pinpoint where the quakes occurred thanks to NASA’s Mars Reconnaissance Orbiter (MRO). Scientists looking at images from the orbiter noticed craters on the surface left by each of the impacts and were able to determine the dates they formed. Both craters are more than 130 meters in diameter, making them the largest fresh craters observed in the 16 years MRO has been studying the planet. “This is a very unique data set with this magnitude of impact,” said Lilia Posiolova, head of orbital science operations for MRO at Malin Space Science Systems in San Diego, California. When the first images arrived, she says, “it was unlike anything we’d seen before, and we almost did a double take.”

Farewell

Just because InSight is almost complete doesn’t mean discovery will stop. The “Mars Earthquake Office”, based at the Swiss Federal Institute of Technology (ETH) in Zurich, is archiving the data from the mission. Researchers will likely use this information to make new discoveries for years to come, as they did with the decades-old Apollo data collected during earthquakes on the moon. “I’m pretty sure we’re going to do the same with Mars,” says Anna Horleston, a seismologist at the University of Bristol in the UK.

Researchers have already benefited from re-evaluating the InSight data. At first, they could only determine the magnitude of the quakes, but usually not their location. The scientists, led by Géraldine Zenhäusern, a geophysicist at ETH, figured out how to use the polarity of seismic waves from an earthquake to calculate its location. Separately, new techniques such as machine learning are already starting to detect more tremors in the InSight data.

After InSight dies, Mars will be without a seismometer for a while; one was planned for the European Space Agency’s ExoMars lander, but that mission involved cooperation with Russia and has been put on hold since Russia’s invasion of Ukraine.

There is a small chance that a dust devil could blow away the dust covering InSight’s solar panels and extend the life of the mission. But the researchers are getting ready to say goodbye. “It definitely feels like it’s coming to an end,” Horleston says.

This article is reproduced with permission and was first published on October 27, 2022