Marsquakes: NASA mission discovers that Mars is seismically active, among other surprises
Posted February 24, 2020 11:00 a.m. EST
CNN — It's not just Earth that's shaking these days.
A NASA mission on Mars has recorded evidence of seismic activity, including 174 seismic events across Mars--and 20 events with a magnitude of three or four.
Evidence of seismic activity on Mars that surprised the NASA team is part of a suite of six studies, published Monday in the journals Nature Geoscience and Nature Communications, capturing those first 10 months.
Since landing on Mars in November 2018, NASA's InSight lander has been performing an extensive doctor's checkup on the red planet, revealing some results that surprised InSight's science team.
While the instruments onboard InSight were designed to capture two years worth of data, the seismometer, which measures Marsquakes, returned that intriguing data about Mars in much less time.
"We're using geophysics to probe the deep interior of Mars. For the first time, we've established that Mars is a seismically active planet," said Bruce Banerdt, InSight's principal investigator. "That activity is greater than that of the moon, but less than on Earth."
To be clear, a four magnitude Marsquake doesn't feel the same as it would on Earth because the events on Mars occur deeper beneath the surface than they do on Earth.
If you were standing directly over the spot when a Marsquake happened, you might sense motion, but it wouldn't cause any damage, said Suzanne Smrekar, InSight's deputy principal investigator.
Still, confirming that Mars is seismically active was a major thrill for Insight's team.
"We've been planning this mission for the last ten years, so it's been a long road to get these results," said Bruce Banerdt, InSight's principal investigator.
Mars doesn't have tectonic plates, unlike Earth, so its quakes occur through long-term cooling of the planet and other processes, scientists say. The brittle outer layers of the crust on Mars have to fracture to maintain themselves on the surface.
And Mars isn't a perfect sphere, so the contractions of the crust cause stress and quakes to occur in some areas more than others, Smrekar said.
An analysis of the seismic waves detected by InSight revealed that the upper part of the Martian crust, the top six miles down from the surface, is "pretty broken up." It's another testament to the planet's quake activity and fracturing.
"This is the first mission focused on taking direct geophysical measurements of any planet besides Earth, and it's given us our first real understanding of Mars' interior structure and geological processes," said Nicholas Schmerr, an assistant professor of geology at the University of Maryland and a co-author of the seismicity study. "These data are helping us understand how the planet works, its rate of seismicity, how active it is and where it's active."
This is just the beginning of the data and secrets InSight can reveal about Mars, the scientists said.
Since the mission began, InSight has registered 450 Marsquakes in its catalog, coming from all across the planet and likely due to different causes, like landslides.
There has been an increase in small, low-frequency Marsquakes since early in the mission, Banerdt said. But they've yet to record any large Marsquakes, which is a goal of the mission.
There is no pattern to the quakes, but the increase in small quakes has them wondering if they are related to the Martian orbit or seasons, atmospheric changes or other unknown factors and phenomenon. For now, they remain odd and mysterious.
The InSight team members are still hopeful for big quakes in the future as well.
Two other InSight investigations, including the heat probe taking Mars' internal temperature and the Rotation and Interior Structure Experiment investigating Mars' core will provide more data as the mission continues.
A fascinating landing site
Originally deemed a flat parking lot by NASA scientists, InSight's landing site along the Martian equator is more interesting than previously believed based on ten months of studying it.
InSight landed in an impact crater in Elysium Planitia. The surface is smooth and sandy with some rocks strewn about. The plains of Elysium Planitia, found along the Martian equator, are between highlands to the south and west and volcanoes to the north and east.
Surprisingly, the scientists discovered that it was the Cerberus Fossae fault lines that revealed the most recently geologically and volcanically active areas on Mars to date. The region is 994 miles to the east and also shows evidence of channels that once carried volcanic flow and liquid water.
The data meant volcanic flows occurred in the area within the last ten million years. Quakes are also registering from that area.
"If you take the thermal model of Mars, you wouldn't expect such recent volcanism," Smrekar said. "We wouldn't expect it to be hot enough inside to be producing magma. This says there is some variability at depth on Mars and the source is not obvious at the surface. Something is allowing localized pockets of volcanism to occur."
Surprising magnetic fields
Previous missions orbiting Mars have revealed that the planet no longer has a global magnetic field like Earth, yet scientists know it did in the ancient past.
The planet's protective magnetic field mysteriously disappeared around 4.2 billion years ago as Mars cooled. The sun's solar wind then stripped away the Martian atmosphere, leaving behind the thin one the planet has today.
InSight's magnetometer is the first instrument of its kind on the Martian surface and it unexpectedly detected that there are steady, localized magnetic fields 10 times stronger than predicted at the surface of the landing site.
These the fields are coming from magnetized volcanic rocks beneath Elysium Planitia, which formed when Mars had a global magnetic field. Those magnetic field particles became trapped in the rocks as they cooled, ensnaring the magnetization inside.
Because the subsurface of Mars didn't heat up again to release that magnetization, the rocks remained the same ever since, said Catherine Johnson, the magnetometer co-investigator.
"The ground-level data give us a much more sensitive picture of magnetization over smaller areas, and where it's coming from," said Johnson. "In addition to showing that the magnetic field at the landing site was ten times stronger than the satellites anticipated, the data implied it was coming from nearby sources."
A unique weather station
InSight also has a weather station simultaneously recording pressure, temperature and wind; it's unlike any meterological suite ever used on Mars. Understanding how the atmosphere behaves at the Martian surface is key to understanding Mars and its ancient past.
Combined with the magnetometer, the scientists were able to detect 10,000 pressure vortexes moving through the landing site. They believe the vortexes could be the iconic Martian dust devils that spin up columns of dust along the surface, said Philippe Lognonne, principal investigator of the magnetometer.
Trouble with the heat probe
Unfortunately, the heat probe that was deployed last year immediately ran into difficulty as it hit tough, clod-like dirt material 35 centimeters beneath the surface. The probe is supposed to hammer 9 to 16 feet beneath the surface to test how Mars internal temperature varies.
But the self-hammering probe only works if there's friction in the soil, otherwise it bounces in place. The probe team will try another tactic, using the lander's robotic arm to push down on the probe in hopes of continuing the investigation, Banerdt said.
Although they have more data than conclusions, the scientists likened their first 10 months to geophysicists trying to investigate Earth in the early 1900s, using the best tools they had to understand plate tectonics and earthquakes.
"This is an entire new world of processes for us, learning how to categorize these signals," Banerdt said. "It's still a very mysterious situation and we're In the wild west of understanding what's going on. We anticipate that within the next year, we can use this data to probe the deepest structures of Mars."