Yes, Marsquakes Exist. But How Do They Compare To SoCal's Earthquakes?

InSight's seismometer sitting on the martian surface, protected by a shield. ((Courtesy NASA/JPL-Caltech))

Earlier this week, the Jet Propulsion Laboratory announced that its InSight team had detected what it thought was a marsquake (an earthquake..on Mars).

They identified it from a faint signal, picked up between wind on the Martian surface, and movement of InSight's robotic arm.

"It's like maybe a magnitude ... two or something like that," said Bruce Banerdt, Principal Investigator for the InSight Mission to Mars.

A big part of the mission is to measure marsquakes and to interpret how waves travel through the planet, so that researchers can better map its interior.

InSight has its roots at NASA's Jet Propulsion Laboratory, located in Southern California, one of the most seismically active (and seismically exciting!) locations on Earth. But working with quakes on Mars isn't exactly the same as studying them here.

Here are some of the similarities and differences.

QUAKES ARE WAY LESS FREQUENT ON MARS (AS FAR AS WE KNOW)

It took nearly two months before the InSight team registered a marsquake. Compare that to Southern California, which experiences an earthquake roughly every three minutes.

"I would say that making measurements in Southern California is sort of like standing in the median of a freeway during rush hour when all of the cars are rushing by. Versus standing on a little country road in the middle of the night when there's absolutely nothing happening," said Banerdt.

THEY'RE CAUSED BY DIFFERENT PROCESSES

Marsquakes occur primarily because of the cooling and contracting of the planet.

"As Mars cools down from its formation four and a half billion years ago, it shrinks." said Banerdt. "Things cool, they contract, and as the planet contracts, the brittle crust around it has to accommodate itself to a smaller and smaller sphere, so it crinkles up. That crinkling causes faults — which cause marsquakes."

The movement of magma and meteorite impacts can also register on InSight's equipment.

In contrast, quakes on Earth are largely caused by the movement of tectonic plates (which do not exist on Mars).

SCIENTISTS ARE USING ULTRA-SENSITIVE EQUIPMENT TO MEASURE MARSQUAKES

In order to capture the faintest of signals passing through the red planet, scientists are using equipment that can measure background noise at a subatomic level. That's more sensitive than the equipment we use to monitor plate tectonics here.

"You'd never be able to use that kind of sensitivity on the earth," said Banerdt. "No matter where you go on the earth, even if you go to a middle of a continent somewhere, you're still seeing a thousand times more noise, just from the background, than you do on Mars."

Mars is extremely quiet, while background noise on Earth comes from everything from the movement of our oceans to turbulence in the atmosphere.

BOTH QUAKES ARE EQUALLY VALUABLE TO FIGURING OUT THE HISTORY OF THE PLANETS THEY OCCUR ON

"It's almost like we're going back to the early 1900s when we were first doing the seismology on the earth and made the first measurements of the thickness of the crust and the size of the core," said Banerdt.

The difference, he says, is better instruments and better computational techniques.

Scientists are hoping that studying the interior of Mars can offer insight into its creation and composition in much the same way it did for our understanding of Earth.