Mars InSight lander yields new data, crust to core | Popular Science

NASA’s InSight lander first touched down on Mars in 2018, armed with a bevy of instruments to help Earth-bound scientists run a full physical exam on the planet. One of InSight’s main sensors was the first seismometer to measure the red planet’s pulse since the Viking landers in the 1970s.

It took about a year, but the detector began sniffing out so-called Marsquakes in early 2019. Now, three different studies based on InSight’s seismic data, all published yesterday in the journal Science, give us an unprecedented look inside our planetary neighbor.
Using measurements from around 10 Marsquakes, along with knowledge of Mars rocks acquired through Martian meteorites and other Mars data, the teams were able to divine new knowledge about the structure and evolution of the red planet. One study focused on finding the size and characteristics of the crust of Mars, one on the mantle (or middle layer), and one on the core of the planet.

The Marquakes were only a magnitude of 3 or 4, so they would hardly be felt if they occurred on Earth, says Amir Khan, the lead author on the study of the Martian mantle and a geophysicist at the Institute of Geophysics at ETH Zurich.
“This stuff is just amazing,” says Gretchen Benedix, an astrogeologist at Curtin University in Australia and the Planetary Science Institute, who was not involved in the studies. She says it’s a good sign that though the three teams operated separately, they converged on a similar picture of Mars. Benedix has studied Martian meteorites and uses machine learning to study the evolutions of planetary surfaces.


One of the surprises unearthed (or un-Mars-ed?) is that Mars has an unexpectedly large core; its radius sits at the upper end of what scientists previously estimated. The planet’s heart of liquid metal actually starts about 1500 kilometers down from the surface, just halfway to the center of Mars, making the iron and nickel core bigger but also less dense than scientists thought when the mission began.
Another of the studies got a handle on the thickness of the Martian lithosphere—the cool and brittle top portion of the planet that includes both the crust and the outer, colder parts of the mantle—which the authors now think is about 400 to 600 kilometers thick. For comparison, although Earth is much larger (two times the diameter of Mars, in fact), Earth’s lithosphere averages around just 100 kilometers from top to bottom.