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NASA’s robotic lander, InSight, has just allowed us to look inside a planet other than Earth for the first time.

More than two years after launch, seismic data collected by InSight gave researchers a hint of how Mars formed, how it evolved over 4.6 billion years, and how it differs from Earth. A set of three new studies published in Science this week suggests Mars has a thicker crust than expected, as well as a molten liquid core that is larger than we thought.

In the early days of the solar system, Mars and Earth were pretty much alike, each covered by an ocean covering the surface. But over the next 4 billion years, Earth became temperate and ideal for life, while Mars lost its atmosphere and water and became the barren wasteland we know today. Finding out more about what Mars looks like from the inside may help us understand why the two planets had such different fates.

“Moving from [a] “We can really expand the family tree of understanding how these rocky rocks are,” said Mark Panning, InSight mission scientist, during a NASA press conference. planets are formed, how they are similar and how they differ ”.

Since InSight landed on Mars in 2018, its seismometer, located on the planet’s surface, has recorded more than a thousand different earthquakes. Most of them are so small that they will be invisible to a person standing on the surface of Mars. But some of them were big enough to help the team get a first glimpse of what’s going on underneath.

NASA / JPL-Caltech

Marsquakes create seismic waves that a seismometer detects. The researchers created a three-dimensional map of Mars using data from two different types of seismic waves: shear waves and pressure waves. Shear waves, which can only pass through solids, are reflected from the planet’s surface.

Pressure waves are faster and can travel through solids, liquids and gases. Measuring the difference between the time of occurrence of these waves allowed researchers to locate earthquakes and provide clues to the internal structure.

One team, led by Simon Steler, a seismologist at ETH Zurich, used data from 11 strong earthquakes to study the planet’s core. From the way the seismic waves bounced off the core, they concluded that it was made of liquid nickel-iron, and that it was much larger than previously thought (2230 to 2320 miles wide) and probably less dense.