Mars may have a solid inner core like Earth does

A new analysis of Mars’ seismic activity suggests the planet may have a solid inner core within its liquid outer core. This may help solve some mysteries about Mars’ geology, but not everyone is convinced.

“It would be a big deal if it were true,” he says. Simon Stehler from ETH Zurich in Switzerland was not involved in the research. “The seismic evidence for that is pretty thin.”

A few years ago, NASA’s InSight lander allowed researchers to look directly into the interior of Mars for the first time. From 2018 to 2022, onboard seismometers recorded waves generated by hundreds of fire quakes reverberating inside Mars. This allowed Stähler and his colleagues to pinpoint the edges of the large liquid core.

now, San Daoyuan and colleagues from the University of Science and Technology of China also analyzed the InSight data. They looked for waves that may have passed through Mars’ core and “stacked” them together to amplify and identify weak signals reflected from deep within Mars.

The researchers identified two important wave phases. One passed through the center of Mars and back, arriving at the seismometer faster than it would have if the entire core was liquid. The second phase appeared to bounce off the boundary between the liquid outer core and the solid inner core.

Both of these wave phases suggest that Mars has a solid inner core with a radius of about 600 kilometers. “We looked at it twice,” Sun says. That means the solid center of the core is less than one-fifth the radius of Mars itself, similar to the size ratio of Earth and its solid inner core.

“I think they have great preliminary seismic results that will cause some controversy,” he says. Nicholas Schumer at the University of Maryland. “Previous seismic studies of the core suggest it was liquid, but we have not been able to conclusively rule out a small solid inner core. That is not impossible.”

Stehler said he and other researchers reviewed all of the InSight data and found no similar signals. He also said that processing data from seismographs in different ways can yield different results, and that a little “black magic” may be required to interpret the data correctly. states.

Still, Stehler was open to Innercore’s potential. “This is a fresh group with a new perspective on data,” he says. “Maybe they saw something we didn’t see.”

The existence of an inner core could help answer unanswered questions about Mars. For example, given Mars’ known mass, a large fully liquid core can only be explained if Mars was formed from more lighter elements than Earth. A dense inner core solves that problem, Stehler says. “That means Mars was formed from more or less the same material as Earth.”

The discovery also raises new questions about why Mars doesn’t have a geomagnetic field, it said. david stevenson at the California Institute of Technology. On Earth, the solid inner core causes convection within the liquid outer core, which generates the planet’s magnetic field. If Mars has a similar nuclear structure, why doesn’t it have a similar magnetic field?

doug hemingway One explanation could be how the inner core grows, said a University of Texas at Austin professor who co-authored the new study. The Earth’s core freezes from bottom to top, causing convection. On Mars, the inner core could form differently. As the outer core cools, iron crystals could “snow” from its edges and collect in the center of Mars.