Looking deeper beneath the surface of the Earth, it can tell us a lot about its history and geological structure, just like on any other planet.
The InSight lander on the surface of Mars has provided us with our first comprehensive look at what lies just below the surface of the red planet.
A seismometer aboard InSight, called SEIS or “Seismic Experiment for Internal Structure”, indicates a shallow sedimentary layer sandwiched between solidified rocks, resulting from lava flows descending to a depth of about 200 meters or about 650 feet.
This can tell us a lot about how Mars originally formed, how it evolved over time, and the geological factors that are still at work today. In particular, lava flows may be related to what we know about the planet’s volcanic past.
Above: Image of the InSight lander in Manor Hollow, a small impact crater made by the artist.
“Seismic surveys of shallow subsurface layers around the InSight landing site have so far been limited to the top 10-20 m using seismic travel time measurements and soil conformity assessments, with the result that structures from a few tens to several hundred meters have not been mapped.” , – the researchers explain in their article.
InSight arrived on Mars in November 2018, landing on a wide and flat plain known as Elysium Planitia. Here, the lander’s instruments measured the subtle ambient vibrations of the earth caused by the winds over the planet’s surface to figure out what was out of sight below.
The same method was developed on Earth to assess the composition of the subsurface and the associated risk of earthquakes. On Mars, the wave pattern corresponded to two dense layers of rocks, such as basalt, with a thinner and less dense layer of material in the middle, most likely sedimentary in nature.
From what we know about the history of Mars from the craters that are still visible on the planet today, researchers suggest that the top layer of solidified lava is about 1.7 billion years old, formed during the cold, dry Amazonian period on Mars, when Mars was relatively few meteorites. and collisions with asteroids.
A deeper layer of approximately 3.6 billion years, created during the Hesperian period, when there was much more volcanic activity on the Red Planet. These ancient periods turned Mars into the planet we see and study today.
“This helps tie that into trying to figure out how long it was between different activities,” geophysicist Bruce Banerdt of California Institute of Technology’s Jet Propulsion Laboratory told Inverse.
“The fact that you have a sedimentary layer sandwiched between these two volcanic rocks suggests that there has been a pause in volcanic activity, quite a long pause because it takes a long time for sedimentary rocks to form.”
The presence of this middle layer with a thickness of about 30-40 meters (98-131 feet) is something of a surprise to researchers, and it is not entirely clear what it is made of and how it was formed. There may be some mixing with Amazon basalts, but the accuracy of the seismic readings decreases at shallower depths.
Part of the usefulness of this data lies in figuring out if life ever existed on Mars, but it also tells us more about the history and evolution of the Earth – Earth and Mars are actually very similar in terms of geological composition.
Aside from ancient planetary history, there is a more immediate benefit to knowing what lies beneath the surface of Mars at different points: this allows scientists to determine the best locations for lander, rover, and (ultimately) space stations in the future.
“While the results help to better understand the geologic processes in Elysium Planitia, comparison with pre-landing models is also useful for future ground missions as it can help refine predictions,” says seismologist Brigitte Knapmeier-Endrun of the University of Cologne. Germany.
Research published in Nature Communications…