Last November, NASA’s InSight Lander dropped onto the surface of Mars to begin its mission of exploring the planet’s interior and detecting seismic activity. The Jet Propulsion Laboratory just announced it completed one of those goals on April 6 when it recorded a tremor or “marsquake” on the planet, the first quake recorded outside of the Earth or the Moon.
The faint signal was detected by the Seismic Experiment for Interior Structure (SEIS) instrument placed on the surface of Mars in December next to the stationary lander, which has a 19-foot wingspan, including its solar panels. Analysis shows the tremor, which shook between magnitude 2 and 2.5 on the Richter Scale, appears to have come from the interior of the planet and was not caused by wind. The same type of tiny quakes occur in Southern California almost every day and are not noticeable.
“InSight’s first readings carry on the science that began with NASA’s Apollo missions,” Principal Investigator Bruce Banerdt of NASA’s Jet Propulsion Laboratory says in the release. “We’ve been collecting background noise up until now, but this first event officially kicks off a new field: Martian seismology!”
Meghan Bartels at Space.com reports that researchers don’t expect Mars to have the same types or frequency of quakes as Earth. That’s because, unlike Earth, where dozens of tectonic plates bash into one another creating faults, Mars is composed of one large single plate. However, that plate still has the potential for shaking, researchers suggest, as the slow cooling and contracting of the plate breaks the crust and sends ripples through the interior. The recently detected temblor seems to confirm that theory.
The SEIS also picked up three other tiny quake signals that are ambiguous and unconfirmed. All the potential shakes are too small to give researchers much insight into the planet’s interior, but it is beginning to reveal how seismically active the planet is. The size and duration suggests that the rumble was more akin to what scientists have found on the moon versus on Earth.
“We thought Mars was probably going to be somewhere between Earth and the Moon [seismically]” Renee Weber, a planetary scientist at NASA’s Marshall Space Flight Center tells Alexandra Witze at Nature News. “It’s still very early in the mission, but it’s looking a bit more Moon-like than Earth-like.”
The signal is too weak to reveal exactly where it came from in Mars interior, and it’s possible it was caused by a meteorite hitting the surface. But as researchers gather more data from more and hopefully larger marsquakes, the hope is that all the energy bouncing around the planet can be used like a planetary x-ray, revealing the size and composition of the planet’s core and interior.
The marsquake came just in time, too. Maya Wei-Haas and Michael Greshko at National Geographic report that after waiting 128 days for a signal, researchers were getting impatient with the SEIS. “For the first month, it was like, ‘This is fine, this is fine, no problem,’” Banderdt says. “And then getting to the second month we’re going, ‘Eh, anytime now, go ahead Mars, do your stuff.’
Now that they’ve detected the first quake, the team anticipates they’ll detect many more quakes over InSight’s two-year mission, hopefully enough to create a model of the planet's insides.