NASA's InSight lander has detected its three most powerful marsquakes yet, potentially giving scientists an even clearer picture of the Red Planet's interior.
InSight spotted 4.2- and 4.1-magnitude temblors on Aug. 25, then picked up another roughly 4.2-magnitude quake on Sept. 18 that lasted for nearly 90 minutes, NASA officials announced on Wednesday (Sept. 22).
The previous record holder, which InSight measured in 2019, clocked in at magnitude 3.7 — about five times less powerful than a 4.2-magnitude quake.
InSight (short for "Interior Exploration using Seismic Investigations, Geodesy and Heat Transport") touched down near the Martian equator in November 2018, tasked with probing the planet's interior like never before.
The solar-powered lander's main science instruments are a burrowing heat probe and a supersensitive suite of seismometers. The mission team is also using InSight's communications gear to precisely track its location on Mars. This information reveals how much the planet is wobbling on its axis, which sheds further light on its interior structure.
The heat probe, nicknamed the "mole," was shut down earlier this year; it never managed to get very far underground, stymied by Martian dirt that was unexpectedly difficult to dig in. But the seismometers have been very productive, recording and characterizing hundreds of marsquakes to date.
Analysis of these temblors has allowed the InSight team to map out the Martian interior in detail. For example, the lander's observations have revealed that the Red Planet has a surprisingly large core and relatively thin crust.
The newly detected marsquakes could help sharpen this picture. The InSight team is still studying the Sept. 18 quake, but mission researchers have already characterized the Aug. 25 events to some degree. For example, they've determined that the 4.2-magnitude temblor originated about 5,280 miles (8,500 kilometers) from InSight.
It's the most distant quake the lander has ever detected, NASA officials said. And it's much farther away than the region that has spawned nearly all of the powerful quakes detected so far by InSight — Cerberus Fossae, an area about 1,000 miles (1,600 km) from the lander where lava may have flowed just a few million years ago.
The epicenter of Aug. 25's 4.2-magnitude quake remains unclear.
"One especially intriguing possibility is Valles Marineris, the epically long canyon system that scars the Martian equator," NASA officials wrote in an update Wednesday. "The approximate center of that canyon system is 6,027 miles (9,700 km) from InSight."
The 4.1-magnitude temblor from Aug. 25 occurred much closer to the lander — about 575 miles (925 km) away. And it sported fast, high-frequency vibrations, whereas the 4.2 event's shaking occurred in lower frequencies, NASA officials said.
"Even after more than two years, Mars seems to have given us something new with these two quakes, which have unique characteristics," InSight principal investigator Bruce Banerdt, of NASA's Jet Propulsion Laboratory in Southern California, said in Wednesday's update.
InSight and its handlers overcame considerable adversity to make the newly reported detections. Lots of dust has accumulated on the lander's solar panels since touchdown, reducing its power output dramatically. This problem was compounded recently by Mars' orbital path, which took it farther and farther away from the sun. (The Red Planet reached aphelion, its farthest point from our star, on July 12.)
So the mission team temporarily turned off several instruments to save energy — which InSight's heaters needed more of to deal with the falling temperatures — and cleared some of the dust away. They did this by using the lander's robotic arm to trickle sand onto InSight's solar panels. As the Martian wind swept these granules away, they carried some dust with them.
These efforts allowed InSight to maintain relatively steady power levels through aphelion, team members said.
"If we hadn't acted quickly earlier this year, we might have missed out on some great science," Banerdt said.
The InSight team is considering whether to conduct additional dust-cleaning operations. Such activities, however, would have to wait until after solar conjunction, the period when Mars is on the opposite side of the sun from Earth. NASA suspends communications with Red Planet spacecraft during this time, as commands can be corrupted by solar interference.
The InSight team will stop commanding the lander on Sept. 29, likely for about two weeks. The moratorium on commanding Mars spacecraft ends on Oct. 14, NASA officials said.
Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.