After some 3 years on the surface of Mars listening for seismic tremors and collecting other data, the end is near for NASA’s InSight lander. As a result of dust collecting on the probe’s power-producing solar panels, its science operations will end in July, NASA officials announced today, with a complete shutdown expected by the end of the year.
Even as they prepare to say goodbye to the leggy lander, however, researchers are celebrating its accomplishments. They include measuring the magnetic field of Mars and detecting more than 1300 quakes, which have enabled researchers to map the planet’s depths. The mission has been “an important first step in studying the interior of Mars,” says Paula Koelemeijer, a seismologist at the University of Oxford.
Launched in May 2018, InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) landed that November on the Elysium Planitia, a broad, flat plain on the martian equator. The locale might seem uninspiring, but it was perfect for the stationary lander. Here, it could deploy its ultrasensitive seismometer, which required calm, nearly silent weather conditions in order to detect seismic waves from distant marsquakes, rebounding off the interior of the planet.
After the team switched on the instrument in February 2019, however, it heard nothing for 2 months. “We were rather nervous,” recalls John Clinton, a seismologist from ETH Zürich and a co-investigator on the mission. One fear was that any marsquakes were too faint to be detected.
But those fears were allayed in April 2019 when InSight detected its first quake. Since then, more than 1300 have been documented by Clinton’s Marsquake Service, which analyzes InSight’s daily seismic data. One, detected on 4 May, was a monster magnitude 5 marsquake. “It was as large as all of the other quakes seen until then combined,” says Brigitte Knapmeyer-Endrun, a planetary seismologist from the University of Cologne. Many of the quakes originate in the nearby Cerberus Fossae region, but their causes remain largely unknown. Possibilities include remnant volcanic activity, stresses in the crust, or meteorite impacts.
The quake data have given scientists a better understanding of the planet’s structure. Prior to InSight’s arrival, for example, some researchers expected to find a relatively meager and solid planetary core. Instead, “It’s a really big core, which was unexpected,” says Julia Semprich, a planetary scientist at the Open University, proportionally as big as Earth’s. And it is molten—like Earth’s outer core; it is not clear yet whether the inner core is also liquid, or solid like Earth’s.
InSight also provided glimpses of the composition and thickness of the martian mantle, the layer sandwiched between the planet’s core and crust. It appears to consist of just a single rocky layer, rather than two like Earth. The thin martian crust, meanwhile, appears to have either two or three layers, with possible evidence for water buried inside.
“We now have a map of the inside of Mars,” says Bruce Banerdt of NASA’s Jet Propulsion Laboratory (JPL), the lead on the mission. The details are helping researchers understand “how it formed from the solar nebula 4.5 billion years ago” and then evolved.
InSight’s other key findings include documenting a magnetic field that is 10 times stronger than expected, and evidence of lava flows at its landing site. Results from a radio instrument designed to track the wobble of Mars and more precisely measure its core have yet to be released.
The $425 million mission hasn’t been all plain sailing. A heat probe designed to be hammered into the ground to measure subsurface temperatures couldn’t penetrate the tough surface. “That was the biggest disappointment of the mission,” Banerdt says.
Still, Yosio Nakamura, a planetary seismologist at the University of Texas, Austin, is thrilled researchers have been able to get so much information from InSight’s single seismometer. “I thought the results would be rather limited,” Nakamura says. “But [researchers are] still getting very interesting results.”
Soon, however, InSight will not have the power to keep transmitting. Its dusty solar panels are now generating just one-tenth of the power they were making at the mission’s start, NASA officials said at a press conference today. Hopes that a passing dust devil would clean the panels have not come to pass, although that “could still happen” Banerdt says. But if it does not, “At the end of the calendar year, we anticipate to conclude all operations,” said JPL’s Kathya Zamora Garcia, InSight’s deputy project manager.
Researchers are already beginning to dream of how they might follow in InSight’s footsteps. Some are planning a seismometer network for the Moon, for example, whereas NASA’s Dragonfly mission is scheduled to take a seismometer to Saturn’s moon Titan in 2026. Venus or Jupiter’s icy moon Europa are also attractive targets. The InSight mission, Banerdt says, “has shown seismology for the incredibly capable technique it is.”