Surprise! The first peek inside Mars reveals a crust with cake-like layers

Image of NASA's InSight spacecraft with the instruments used on the Martian surface

The Mars InSight machine is equipped with a curved seismometer (left) and a probe for measuring heat flow (right).Credit: NASA / JPL-Caltech

NASA’s InSight mission has finally looked inside Mars – and discovered that the planet’s crust may be made up of three layers. This is the first time that scientists have directly studied the interior of a planet other than Earth, and will help researchers discover how Mars has formed and evolved over time.

Prior to this mission, researchers had only quantified structures within the Earth and Moon. “This information has been missing, so far, from Mars,” said Brigitte Knapmeyer-Endrun, a seismologist at the University of Cologne in Germany, in a pre-recorded speech delivered at a preliminary meeting of the American Geophysical Union on 15 December. . She declined to be interviewed Nature, says the work is being considered for publication in a peer-reviewed journal.

It is a key find for InSight, which landed on Mars in November 2018 with the goal of working out the planet’s internal structure.1. The InSight surface scrubs near the martian equator, on a flat surface called Elysium Planitia, and uses a highly sensitive seismometer to listen to geological energy erupting through the planet.2. To date, the mission has discovered more than 480 ‘marsquakes’, says Bruce Banerdt, the mission’s chief investigator and scientist at the Jet Propulsion Laboratory in Pasadena, California. Mars is less active than Earth, but larger than the Moon.

Just like with Earthquakes on Earth, seismologists use marsquakes to map the inner structure of the red planet. Seismic energy travels through the earth in two types of waves; by measuring the differences in how these waves move, researchers can work out where the planet’s heart, costume, and crust begin and end, and shape common to all men. These basic geological sequences reflect how the planet cooled and formed billions of years ago at the time of the eruptive birth of the Solar System. Now, “we have enough data to start answering some of these big questions,” says Banerdt.

The Earth’s continental crust is usually divided into subsets of different rock types. Researchers suspected, but did not know for sure, that the martian bark was also layered, said Justin Filiberto, a planetary geologist at the Lunar and Planetary Institute in Houston, Texas. Now, InSight data shows that it is made up of two or three layers.

Three-layer bark would best suit geochemical models3 and studies of martian meteorites, says Julia Semprich, a planetary scientist at the Open University in Milton Keynes, UK.

Depending on whether the bark has two or three layers, it is either 20 or 37 kilometers thick, Knapmeyer-Endrun said during her speech. That thickness seems to vary in different places around the planet, but it is unlikely to exceed an average of 70 kilometers, she said. On Earth, the thickness of the crust varies from about 5 to 10 kilometers below the oceans, to about 40 to 50 kilometers below the continents.

In the coming months, InSight scientists plan to report measurements taken even deeper in Mars, says Banerdt – ultimately revealing information about the planet’s heart and costume.

Along with listening to marsquakes, another major scientific goal of InSight is to measure the flow of heat through Martian land using a probe called the mole. It was supposed to bury itself deep in the soil, but it has been difficult to do so – at one point even popping out of the ground completely. The mole eventually gained several centimeters deep, Banerdt said, and will try to dig one last hour in the coming weeks before releasing it. “We have what we think is the final game now,” he said.