Marsquake Data Will Solve Lingering Mysteries Beneath the Planet's Surface

On April 6, InSight, the Mars lander that safely touched down on the red planet back in November, delivered a groundbreaking piece of Mars news. The instruments aboard the lander picked up on tiny tremors coming from beneath the planet’s surface: a phenomenon now referred to as a “marsquake.”

Right now, the “marsquake” (you can hear what it sounds like in the above video) is referred to by NASA’s team of planetary scientists as the Martian Sol 128 event. It’s actually one of four readings collected by InSight which occurred on March 14, April 10, and April 11, which NASA publicly announced on Tuesday. But the Martian Sol 128 event was slightly larger than the other events and has sparked excitement from scientists like Mark Panning, Ph.D., a geophysicist at NASA’s Jet Propulsion Laboratory who sees it as the first step to understanding how Mars has developed from the inside out.

“Mercury, Venus, Earth, and Mars, and our own moon are all so-called terrestrial bodies consisting of metallic cores and rocky mantles and crusts, which are very different than the gas giants of the outer solar system,” Panning tells Inverse. “The data from InSight will constrain the composition and temperature structure of Mars, which helps us understand how Mars has evolved over the history of the solar system.”

What Caused the Marsquake?

When not caused by the testing of underground nukes, much of Earth’s own seismic rumblings can be traced down to the movement of tectonic plates, giant plates made up of the lithosphere, Earth’s outer shell. These plates are mobile and shape the features on Earth’s surface when they interact with one another. But there is no evidence of plate tectonics present or past on Mars, says Panning. The marsquake that InSight picked up on was caused by something else.

Instead, Panning explains that Mars has been slowly cooling over millions of years. This cooling is likely the driver behind the marsquake and bears important similarities to “moonquakes,” or non-tectonic plate-derived tremors that were first noticed during the Apollo missions.

"As it loses heat to space, the planet should cool and contract, and this should drive seismicity.”

“The most likely cause for seismicity on Mars is related to its ongoing cooling, which is one proposed cause for the large shallow events, up to around magnitude 5, observed on the moon. As it loses heat to space, the planet should cool and contract, and this should drive seismicity,” says Panning.

Importantly, this reading affirms the same process that we believe underlies the moonquakes may also be at work on mars, but the data that comes from this event may tell us even more about what’s happening beneath the planet’s surface.

What’s Beneath Mars’ Surface?

Geologists are very familiar with the interior of our own planet, which is a metallic core surrounded by viscous layers of molten rock and topped with a rocky mantle and crust. Mars also has a metallic core, which was announced in 2003 and “may be partially liquid,” adds Panning. Philippe Lognonné, Ph.D., a planetary seismologist at the Institut de Physique du Globe de Paris who analyzed the data from InSight’s instruments, adds that we don’t know how big the many layers beneath Mars’ surface actually are.

“We know that mars has a crust, a lithosphere, and a core but do not know precisely the thickness of all these features,” he tells Inverse.

For example, Lognonné says that estimates on the radius of Mars’ core may be off by as much as 300 kilometers. The data from this event will help us go even deeper and figure out how big each layer of Mars’ surface is.

“The larger the seismic energy is, the deeper we will get information,” Lognonné says. “With the dust devils we got at the beginning of the mission, we have been able to get the structure of the first five meters. With the future quakes, we will get this information for the mantle and for the core. Seismology is a lesson in patience.”

"Mars is another patient beyond Earth to help us understand terrestrial planets in general."

Understanding what Mars is actually made of may eventually help us understand how the different conditions of space shape how planets are formed. It’s a peek into the art of universal world-building, and the marsquake data will be our first step into the field.

“My usual analogy is that one does not become a great doctor while only practicing on one patient,” says Panning. “Mars is another patient beyond Earth to help us understand terrestrial planets in general.”