NASA’s Mars probe made the first map of the red planet’s underground by listening to the sound of wind bouncing through layers of soil and rock near the Martian equator.
Making the first map of the Martian ground
The team used instruments aboard NASA’s InSight probe. The spacecraft landed on the Elysium Planitia plain of Mars in 2018 to study the planet’s weak earthquakes. InSight’s data has previously allowed scientists to get a rough idea of the size and composition of the Martian core, as well as the nature of the mantle and thickness of the crust.
A new technique developed and perfected for the first time on Earth allows a team led by Swiss geophysicists to use the probe’s instruments to look directly beneath the dry Martian surface. barren and explore what lies within the first 200 meters of the Martian crust.
“We used a technique developed here on Earth to characterize earthquake-prone sites and study subsurface structure,” said Cedric Schmelzbach, a geophysicist at the Federal Institute of Technology. Swiss canton in Zurich (ETH), and the new study author told Space.com.
“The technique is based on the vibration of the surrounding environment,” says Schmelzbach. On Earth there are oceans, winds, which cause the ground to shake all the time, and the shaking measured at a certain point has the imprint of the subsurface.”
Basically, vibrations on the surface cause the ground to shake. These microscopic vibrations travel deep below the surface and can be detected by sensitive instruments.
Schmelzbach said Mars is much quieter than Earth. There are no oceans on this planet, and Mars’ atmosphere is much thinner, resulting in weaker winds. Not to mention, while geologists on Earth can use an infinite number of stations, on Mars they only have one – the InSight lander.
Still, listening to the interactions of the winds on Mars with the ground beneath the crater and its plains still reveals amazing details.
The billion-year-old evolution of Mars
The map provides an interesting look at the billions of years of Martian evolution. It shows an unexpectedly deep and dense deposit of solidified lava, all covered by a 3m thick layer of sand.
The origin of this sediment remains a mystery. It lies 30 to 70 meters below the surface of Mars, sandwiched between two layers of frozen ancient lava.
Schmelzbach said he is still working on how to explain that and determine the age of this sediment. The researchers compared the two layers of lava embracing the sediment with previous studies of the geology of nearby craters. This data allowed them to pinpoint the origin of lava layers at two important periods in the geological history of Mars, about 1.7 billion years ago and 3.6 billion years ago.
At the top of the younger lava layer, just below the surface layer, is a band of rock about 15m thick. These rocks are likely to have been ejected from the Martian surface after a past meteorite impact, and then fell back down.
In the future, the scientists want to see if they can extend their technique a little further, and look even deeper, into the first few kilometers of the Martian crust.
Earlier studies of the planet’s core, mantle and crust based on InSight data have revealed surprising differences between Mars and Earth. The two planets are often considered twins in the Solar System that each shared an evolutionary path up to a certain point.
Both planets have abundant oceans of water and rich atmospheres. But then, Mars lost its protective magnetic field, causing the solar wind to abrade, the stream of charged particles emanating from the sun gradually separated the planet from its atmosphere, and Mars became an etched planet. harsh as it is today. Scientists hope that the geology of the two planets can provide some clues about their different development paths.
The study was published in the journal Nature Communications on November 23.