Strange structures discovered inside the largest moon on Mars

The two companion moons of Mars are amazing in more ways than one. And the structures astronomers have just discovered in the vault of one of them, Phobos, could help understand their origin.

Phobos is one of two Mars moons. the biggest. But it is still a very small moon compared to ours. Its largest diameter does not exceed 27 kilometers. Its surface is characterized by a huge crater. It has a diameter of about nine kilometers. On the surface of Phobos there are other craters and strange scratches. Not to mention the fact that this young moon seems to want to get relentlessly close to Mars. So much so that he could end up ripping a ring apart within a few tens of millions of years. Lots of features that have intrigued astronomers for a long time now.

And they finally got the chance to see it up close thanks to the Mars Express mission, from the European Space Agency (ESA). It was launched in 2003 to study the internal structure of Mars, and carried on board an instrument called Marsis – to Mars advanced radar for subsurface and ionosphere sounding. Idea: blow up red planet Low-frequency radio waves and analysis of the characteristics of waves returned by the Earth as well as the deep layers.

After a major update to the Marsis instrument software, astronomers were able to collect critical data marking the passage of the first Mars Express pass near Phobos. Less than 85 km. Knowing that the line separating our atmosphere from interplanetary space is located at an altitude of about 100 km, this means … all because “The approach allows us to study its structure in more detail and identify important features that we would not have been able to see from afar. In the future, we are confident that we can use Marsis within 40 km The instrument was originally designed to study Mars at a distance of 250 km. The Mars Express orbit has been optimized to get us as close to Phobos as possible on a few flights between 2023 and 2025, which will give us opportunities to try.”Andrea Sechetti, researcher, identifies at A ESA press release.

Asteroid or rocks torn from Mars?

What the researchers expected is that the Mars Express data could shed light on the origin of Phobos. Because astronomers are still hesitant. It could be the moons of Marsancient asteroids Captured by the red planet. This is what their appearance and composition suggest. But not their orbit. So they could also be, like our moon, bits of rock torn apart by the Martian collision.

The data obtained on September 23 is rich and its analysis is still in its infancy. However, researchers have already identified in “radar”, signs of more or less harmful superficial structures. But also, the faint signs of what appear to be underground features are more interesting. A multi-layered structure could indicate that Phobos is indeed an ancient asteroid. But who can also refer to a constitution in “a pile of floating rubble”.

The following nearby passes from the Mars Express in the skies over Phobos should let us know more. And the task Exploring the moons of Mars (MMX), in cooperation with the Japan Space Agency, which should land on Phobos soon – not earlier than 2024 in the same way – to sample collection It should help clarify things more. After returning to Earth in 2029, these samples should indeed make it possible to finally solve the mystery of the origin of Mars’ moons.