Compared to Earth, Mars is a geologically dead planet. It doesn’t have a core of liquid iron generating a magnetic field like Earth does, and there’s no plate tectonics involved – unlike Earth, the Red Planet’s crust hasn’t been folded up. outside the planet and extruded again in a continuous folding process over billions of years.
And scientists have long thought that the Martian crust, the planet’s outermost layer, was a simple affair, and certainly not as varied as the Earth’s crust. But new research published Friday in the journal Geophysical Research Letters uses evidence from meteor strikes to suggest that Mars’ subsurface is not as simple as it looks, or as expected.
The surface of Mars is basalt rock, that is, material deposited in the form of molten lava. But researchers have found higher concentrations of silicon in material excavated miles below the surface by meteorite impacts, and silicon should not be present in such quantities in basalt rock, according to the assistant science professor. of Earth and Environment from the University of Iowa and corresponding author of the study, Valérie Payré.
“There is more silica in the composition which makes the rocks not basalt, but what we call a more evolved composition,” Dr. Payré said in a statement. “This tells us that the crust formed on Mars is definitely more complex than we knew. So it’s more about understanding this process, and especially what it means for the formation of the Earth’s crust.
Using images from NASA’s Mars Reconnaissance Orbiter, Dr Payré and his colleagues found high concentrations of silicon in nine places – impact craters and other cracks or fractures on the surface – in the Martian southern hemisphere.
Scientists believe Mars formed 4.5 billion years ago, possibly as part of a collision between massive rocky bodies in space. Such a collision could have turned the entire planet into a gooey liquid magma mess, an “ocean of magma”, on which a thin crust eventually froze.
If portions of primordial Mars remained solid after such a collision, remaining as islands in the ocean of magma, this could explain areas where the crust is more silicon than basalt. The researchers dated the crust at all nine locations to be 4.2 billion years old, the oldest crust identified on Mars to date.
“There were rovers on the surface that observed rocks that were more silicic than basaltic,” Dr Payré said. “So there were ideas that the crust might be more silicic. But we never knew, and we still don’t know, how the first crust formed, or how old it is, so it’s still kind of a mystery.
Studying the crust of Mars can help scientists better understand how the Earth formed in its ancient past. Since our planet has been geologically active, much of the oldest crust has been recycled by plunging back into the interior of the planet in subduction zones where tectonic plates meet.
“We don’t know our planet’s crust from the beginning; we don’t even know when life first appeared,” Dr. Payré said. “Many believe the two might be related. So understanding what the crust looked like a long time ago could help us understand the whole evolution of our planet.