The first and only spacecraft to study earthquakes on Mars is about to die. A Martian storm recently covered the solar panels of NASA’s Insight lander with dust, blocking out much of the sunlight it needs to charge its batteries. Mission monitors now operate the seismometer intermittently to conserve energy. Within weeks, the spacecraft will likely stop responding to commands from Earth and slip into oblivion.
The heart of Mars has been measured – and it’s surprisingly large
But InSight won’t come out without fanfare. On October 27, scientists reported that last year, the mission detected seismic waves caused by the largest meteorite impact ever seen on Mars.1And the2. Both meteorites hit the planet with the energy of a small nuclear bomb. By tracking how massive earthquakes ripple through Mars, scientists have been 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 will be located in a geologically unusual place.
The findings add to InSight’s rich discovery heritage. Since arriving on Mars in November 2018, it has collected information about more than 1,300 “swamps”3. This allowed the researchers to calculate, among other things, the long-awaited size of Mars’ core and the thickness of its crust. Just last month, researchers used data from five swamps to determine that the Martian mantle is richer in iron than Earth.4. All this information on the inner layers of Mars will help scientists understand how the planet formed and evolved over billions of years.
“Before the mission, I always showed all these caricatures of planets cut in half,” says Mark Banning, InSight project scientist at the Jet Propulsion Laboratory (JPL) in Pasadena, California. “The cartoon has now gone from question marks and blurred boundaries to a true picture of what’s inside Mars. That was what we promised, and we did.”
It wasn’t always clear that scientists would succeed. In 2012, NASA decided to build and launch the US$994 million InSight, a controversial option because the agency has several other Mars missions already on its waiting list. Then, problems with the construction of the highly sensitive seismometer delayed its launch by two years, worth $150 million. Once InSight finally reached Mars, the German-made instrument nicknamed the Mole, which was supposed to measure heat flow in the soil, failed when it could not bury itself in the ground. The mission didn’t even detect the first earthquake until five months after it landed—and when it finally did, researchers struggled to explain what they were seeing.
“At first, we weren’t really sure how much of the data we could get,” says Brigitte Knappmayer Erdron, a planetary scientist at the University of Cologne in Germany.
Surprise! A first peek inside Mars reveals a layered crust that looks like a cake
But things picked up for InSight during its second Martian year. The spacecraft is located near the Martian equator, in an area 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 magma injections are thought to cause earthquakes.5. In August and September 2021, the spacecraft discovered swamps on the other side of the planet for the first time.6.
And on May 4 this year, InSight detected a 4.7-magnitude earthquake—the largest to date (most of InSight’s detections were in the 2–3 range). On Earth, humans can feel such an earthquake if they are near the epicenter.
“This is a beautiful gift from Mars,” said Philippe Legnone, a geophysicist at the Paris Institute of Geophysics, who leads the seismology team.
The researchers have yet to publish what they’ve learned from the “big thing.” But it was so large that it sent seismic energy through the surface layers of Mars’ 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 exaggerate too much,” says Bruce Banerdt, a geophysicist at the Jet Propulsion Laboratory and Principal Investigator at InSight. “But it really does give information all over the spectrum, from the shallow crust all the way to the deepest mantle and core.”
Meanwhile, scientists analyzed surface waves generated during last year’s record-breaking meteor collision on September 18 and December 24.1And the2. InSight picked them up from thousands of kilometers away.
Ripples through Mars’ crust to the north of InSight, which is near the major geological boundary where the terrain is smoother and less elevated than the cratered southern highlands. The way surface waves travel through the crust to the north indicates that it is denser than the crust beneath Insight, which descended into an area where the rocks are particularly porous.
InSight was able to learn the source of the earthquakes thanks to NASA’s Mars Reconnaissance Orbiter (MRO). Scientists who were looking through images of speckled craters on the surface left by each of the impacts, were able to determine the dates when they formed. Both craters are more than 130 meters wide, making them the largest new craters observed in MRO’s 16 years of studying the planet. “This is a very unique data set with this magnitude of impact,” says Liliya Posiolova, who leads orbital science operations at MRO at Malin Space Science Systems in San Diego, California. When the first pictures arrived, she said, “It was like nothing we’d seen before, and we almost did a double-take.”
Just because InSight is about to end doesn’t mean discovery will stop. The Earthquake Service based in the Swiss Federal Institute of Technology (ETH) in Zurich is archiving mission data. Researchers will likely use this information to make new findings for years to come, as they did with decades-old Apollo data collected during earthquakes on the Moon. “I’m pretty sure we’d do the same with Mars,” says Anna Hurleston, a seismologist at the University of Bristol, UK.
‘Mars earthquakes’ reveal the hidden geology of the red planet
The researchers have already benefited from a reassessment of InSight data. At first, they could only determine the magnitude of the earthquakes, but not usually their location. Scientists led by Geraldine Zenhausrn, a geophysicist at ETH, have discovered how to use the polarity of seismic waves from a swamp to calculate its location.7. Separately, new technologies like machine learning are already starting to detect more quagmire in InSight data8.
Once InSight dies, Mars will remain 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 is on hold in the wake of Russia’s invasion of Ukraine.
There is a small chance that a dust demon will blow the dust covering InSight’s solar panels and extend the life of the mission. But researchers are preparing to say goodbye. “There’s definitely a feeling, ‘Oh my God, this is about to be over’,” Hurleston says.