July 23 (UPI) -- Marsquake data collected by NASA's InSight lander has allowed planetary scientists to more accurately characterize Mars' deep interior, as well as offered clues to the Red Planet's origins.
"Insight has confirmed that our view that Mars is a planet that was once almost entirely molten and separated into a crust, mantle and core as it cooled," Amir Khan of ETH Zurich said Friday during a presentation on NASA Live.
Khan is the lead author of one of three newly published scientific papers buoyed by Insight data.
Since landing in 2018, Insight and its SEIS instrument, a highly sensitive and well-protected seismometer, has been faithfully recording the reverberations rippling through the Martian interior.
Using data from 733 distinct marsquakes recorded by SEIS, scientists have been able to estimate the size and composition of the Red Planet's inner structures.
More specifically, scientists confirmed that Mars boasts a liquid nickel and iron core, a relatively uniform mantle and a thick crust.
"All of this is what we need in order to move onto the next stage, which is to say something how Mars was formed," Khan said. "This paves the way for future seismological missions because we know it works."
On Earth, most quakes are caused by processes related to plate tectonics, but there are not slip faults or subduction zones on Mars.
"Because Mars is smaller, it has a thicker lithosphere," said Sabine Stanley of Johns Hopkins University. "Mars doesn't have plate tectonics; Mars is a one plate planet."
Thankfully, plate tectonics aren't a prerequisite for quakes.
"Even if you don't have plate tectonics, planets still have tectonics in the sense that they crack and deform over time," said Mark Panning, planetary scientist at NASA's Jet Propulsion Laboratory in Southern California.
"Mars, like every planet, is constantly losing heat out to space, and so it's cooling down and shrinking," Panning said.
As Mars shrinks, it cracks and fragments, sending minor reverberations through the planet.
"You also have hot spots forming giant volcanoes that are forming big, heavy rock formations that push down on the rest of the crust," said Panning. "So there are all these forces that are acting on the Martian surface."
None of these forces produce quakes that rival those on Earth -- earthquakes with magnitudes of 7 or higher strike every couple of years.
Of the hundreds of marsquakes recorded by InSight, none were greater than a magnitude 4.
That scientists were able to yield such tremendous insights from small, faraway seismic events is a testament to InSight's SEIS instrument, according to Panning.
"The fact that these events are a thousand kilometers away or more and we can still listen to them is amazing, and it is something we could only do on Mars and not on Earth," he said.
"On Earth, the background is too noisy -- from the oceans, which are constantly lapping against the sides of Earth's crust," Panning said.
The most surprising insight enabled by the new seismic data may be that Mars boasts a rather large core, the scientists said.
"It is on the high end of what we expected, and the density is on the low end of what we thought before the mission," Stanley said.
The core's large size and low density suggests it hosts a plethora of lighter elements, like hydrogen, helium and lithium, in addition to nickel and iron. According to Khan, the composition of Mars' core can provide clues about the planet's formation.
"Mars must have formed right at the start of the solar system," he said. "The need for light materials begs for materials that were further from the sun."
"These light elements in the core also explain why it's still liquid, or molten," Khan said. "Lighter elements lowered the freezing point for the iron-nickel core."
So far, most of the quakes measured by Insight appear to be originating from Cerberus Fossae, a region with a long history of volcanic activity. Scientists estimate lava may have flowed across Cerberus Fossae within the last few million years.
Researchers have yet to record a quake from some of the Red Planets largest volcanoes, but its likely seismic rumblings from prominent volcanic regions like Tharsis are being refracted by the mantle away from Insight's location.
While most of the quakes measured by InSight are magnitude 3, scientists are still hoping to capture a really big marsquake, like magnitude 4.5.
In the meantime, the researchers said they will continue to comb through the plethora of seismic data recorded by SEIS.