First look at Mars’s interior reveals a different picture than Earth

The mystery of Mars’s interior has been revealed thanks to marsquakes.

Using data compiled by NASA’s InSight mission that has detected hundreds of marsquakes since landing on the red planet in 2018, scientists around the globe worked together to map out what’s going on beneath Mars’s surface for the first time. Thicknesses and structures of the crust and upper mantle as well as the revelation of a molten core were detailed across three papers published in Science on Thursday.

The liquid core of Earth’s planetary neighbor is quite a departure from our own planet’s deepest characteristics. Composed mostly of an iron-nickel alloy, the Martian core extends about 1,100 miles out from the center, about halfway to the surface. Meanwhile, Earth’s inner core is also mostly an iron-nickel alloy but it’s a dense, solid ball with a radius under 800 miles. A liquid iron and nickel outer core surrounds it.

The papers also describe the crust layer as being about as thin as Earth’s, only reaching about 15 to 45 miles beneath the surface.

These new conclusions were drawn from measurements taken by InSight’s seismometer, which measures the vibrations of quakes as they rattle through the interior of Mars. By measuring the quakes’ speeds and intensities as they travel throughout the planet’s layers, scientists pieced together a likely idea of the planet’s composition.

InSight’s seismometer sits on the dusty surface of Mars, poised to detect and measure the vibrations of marsquakes.
Credit: nasa/jpl-caltech

While these marsquakes get us closer to confirming the makeup of Mars, these are hypotheses based on available data. Just like we haven’t actually confirmed what makes up the whole interior of Earth, this new understanding of Mars’s interior is our best estimate, albeit a very well-informed and logical estimate.

With all of this new data, scientists are now better equipped to develop a history of the formation of Mars. Learning how other planets form can bring further insight into the formation of our solar system and even our own planet.

Mars is the first planet that humans have been able to map the interior of aside from Earth. The interior of the moon has been mapped through various missions over the decades, including the 2011 GRAIL mission from NASA that gave us the most detailed peak inside to date.

As we learn more about the inside of Mars thanks to InSight, NASA’s Perseverance rover is actively scouring the dusty surface and preparing to grab Martian samples to be sent back to Earth in 2030. Together, these missions and more collectively stitch together more and more information about Mars, from its present conditions to its ancient history.