When NASA’s InSight lander lifts off on Saturday, it’ll have an enormous task ahead of it: analyzing Mars’s mysterious interior and measuring “Marsquakes.” There’s a lot riding on this little lander, since there’s debate about what’s actually going on inside the red planet, a planetary scientist tells Inverse.

Once InSight arrives to Mars on November 26, it’ll use its instruments to get right to work. The thing is, scientists only have some educated guesses about Mars’s subsurface—nothing is really that certain. We know that Mars probably has an inner and outer core, which together encompass about 900 and 1,200 miles (1,500 kilometers and 2,000 kilometers) of space. But there’s still the question of how—and if—“Marsquakes” exist, and what causes them.

“Until the last few years, we were pretty sure Mars’ interior was essentially dead,” Tanya Harrison, director of research at Arizona State University’s Space Technology and Science (NewSpace) Initiative, explains. “We didn’t think Mars had a magnetic field, which meant the core was solid. We also hadn’t seen any evidence of volcanic activity anytime in the geologically recent past.”

According to Harrison, two things changed these prevailing ideas about the red planet: the observation of aurorae by NASA’s MAVEN probe and the detection of methane emissions.

“These are clues that Mars might not be as dead on the inside as we once thought,” Harrison says.

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Artist's rendition of MAVEN orbiting Mars

If there truly are Marsquakes, InSight would be the first lander to detect them. Since Mars does not have plate tectonics that shift around like the ones here on Earth, they could be caused by the magma from volcanoes or even meteorites striking the planet. Using its SEIS instrument, InSight will try and get to the bottom of this.

“[NASA’s] Viking landers had seismometers aboard, but they didn’t really come into contact with the ground,” Harrison says.

No matter what InSight finds in its two-year sojourn, one thing is true: even if Mars isn’t really “dead inside,” it’s still extremely goth. Stay tuned on May 5 to watch the lander lift off from Vandenberg Air Force Base on board a United Launch Alliance Atlas V 401 rocket.