InSight Lander’s First Big Batch of Data Reveals Mars’ Seismic Activity and Surprising Magnetism

On November 26, 2018, NASA’s InSight lander began its perilous descent down to the surface of the Red Planet. Tracking the probe’s progression through the Martian atmosphere, personnel at mission control endured “seven minutes of terror”—a period of absolute helplessness, during which scientists could do nothing but wait with bated breath until their spacecraft confirmed it was safe.

The touchdown was “flawless,” NASA employees announced that day. And in the 16 months since, InSight has proved itself to be well worth the effort. The lander’s first big batch of data, described in a suite of studies published this week in Nature Geoscience and Nature Communications, has pulled back the curtain on many once-mysterious aspects of Mars, including its intriguing seismic activity and surprisingly strong magnetic field.

Shortly after settling near the Martian equator a year and a half ago, InSight got busy, deploying an array of instruments, including several ultra-sensitive seismometers and a burrowing heat probe.

In April 2019, InSight’s seismometer detected its first marsquake: a subtle rumble that hinted that, despite its decidedly non-Earth-like geology, Mars’ interior has its own terrestrial temper. “We’ve finally, for the first time, established that Mars is a seismically active planet,” InSight principal investigator and NASA planetary scientist Bruce Banerdt said during a teleconference on February 20.

Since that first find, the lander has detected more than 450 other tremors of varying severity, including several dozen belched up from the planet’s mantle, roughly equivalent to magnitude 3 or 4 quakes here on Earth, reports Ian Sample for the Guardian. On average, Mars seems to shake more than the moon, but still pales in comparison to helter-skelter Earth. Were they to happen on Earth, most marsquakes would barely be detectable, seismologist Philippe Lognonné tells Ben Guarino at the Washington Post.

Still mysterious, however, is the origin of these extraterrestrial trembles. While earthbound quakes arise when our planet’s tectonic plates grind up against one another, Mars lacks the same internal architecture, leaving researchers puzzled about the source of its quakes.

But two temblors that appear to have arisen from a Martian structure called Cerberus Fossae, a series of deep surface fissures that were recently geologically and volcanically active, have provided researchers with hints, InSight deputy principal investigator Suzanne Smrekar tells the Washington Post. Based on InSight’s data, researchers think pockets of magma may still be moving, cooling and contracting deep in the Red Planet’s innards, causing cracks, then quivers, at its brittle rocky surface, reports Maya Wei-Haas for National Geographic.

Also described in the new finds is a mysterious and persistent hum that pervades the Martian landscape. Though the slosh of Earth’s oceans produces a comparable sound, scientists have yet to suss out a plausible cause for the Red Planet’s curious tune. “It’s extremely puzzling,” Banerdt tells National Geographic.

Another surprise has come from data collected by InSight’s magnetometer, which has picked up on a local magnetic field about ten times stronger than researchers expected to see. Though Mars once had a magnetic north and south like Earth, its internal dynamo, or liquid metal interior, stopped churning billions of years ago, stripping the planet of its global magnetic field. (This change also purged the planet of much of its protective atmosphere, exposing its surface to a barrage of space weather and turning what was once a warm, wet world into a frigid, parched desert.)

But magnetic minerals still exist in Martian rocks, locked in like a time capsule of the planet’s long-gone magnetism. “They’re like little tape recorders,” InSight team member Catherine Johnson told the Washington Post. Combined with a series of pulsating electric currents found in Mars’ atmosphere, these blips of local magnetism may be the source of InSight’s unexpected detection.

“This measurement was our first little tiny taste—one single point—of how much stronger the magnetization might be,” Robert Lillis, a planetary space physicist at the University of California, Berkeley who wasn’t involved in the studies tells National Geographic.

InSight is still fervently collecting data, which NASA is releasing to the public at three-month intervals. Once cache of results, though, has so far been conspicuously absent: readings from the craft’s subterranean heat probe, nicknamed the “mole,” which has been unable to penetrate the cementlike soil that cakes InSight’s landing site. Over the next couple months, mission team members will try to leverage the robot’s arm to help the mole break ground, reports Mike Wall for Space.com.

For the most part, though, things on the Red Planet remain on track, team members report. As Banerdt tells Space.com, “I think we're well on our way to getting most, if not all, of the goals that we set for ourselves ten years ago when we started this mission.”

Katherine J. Wu | | READ MORE

Katherine J. Wu is a Boston-based science journalist and Story Collider senior producer whose work has appeared in National Geographic, Undark magazine, Popular Science and more. She holds a Ph.D. in Microbiology and Immunobiology from Harvard University, and was Smithsonian magazine's 2018 AAAS Mass Media Fellow.