Phobos and Deimos, the two natural satellites of Mars, may have been originated from the debris of a giant collision, a new study finds.
The irregular shapes and size of Phobos and Deimos, the two Martian moons, previously suggested that they were asteroids trapped in Mars’ gravitational field. But in that case, the satellites would have irregular orbits. Instead, they follow nearly circular and equatorial orbits around the Red Planet, contradicting this theory.
Now, two studies have emerged to give an explanation to this phenomenon. One of the studies, led by researchers from the French National Centre for Scientific Research (CNRS) and Aix-Marseille University, states that the only event that could generate satellites with such characteristic surfaces as the ones from Phobos and Deimos is a giant collision.
The other study involved digital simulations that explain how the satellites could have been formed from the debris of a huge impact. This study was led by a researchers team from Université Paris Diderot and Royal Observatory of Belgium, along with the CNRS, Université de Rennes 1 and the Japanese Institute ELSI. It was published in the journal Nature Geoscience.
Theories of how the two moons were created have been around in the scientific community for years, including the one that says that they generated from the debris left from a collision between Mars and a protoplanet, just as the Earth’s moon. But that would not explain how the planet ended up with two small moons, and not a large one like the Earth did. The two independent studies came with the answer for this doubt.
The impact that generated the moons could be the same that created the Borealis basin
The study led by Pascal Rosenblatt, Sébastien Charnoz and other researchers from France, Belgium, and Japan, focuses on a collision that happened on Mars and a protoplanet one-third its size about 100 to 800 million years after the planet’s formation. This is the same crash that generated the vast Borealis basin, located at the north pole of Mars, according to previous research.
The debris ring produced around the planet by the impact, had a mass of 100 quadrillion metric tons, 10,000 times the masses of Phobos and Deimos combined, punctuates Space.com. Researchers explain that the inner part of the debris ring was denser, composed of rubble and magma, while the outer part was a thin layer of gas, dust, and tiny rocks. In the inner part, a large moon one thousand times the size of Phobos was accreted.
Because of the gravitational interactions, this giant moon gathered the rubble in the outer part if the ring to form new, smaller moons, such as Phobos and Deimos. Thousands of years later, a group of about ten small moons and a large one surrounded Mars. After about 5 million years, the planet’s gravitational field began pulling most of these moons, including the large one, which ended up crashing on the globe’s surface. Only Phobos and Deimos survived.
The other study led by researchers from the Laboratoire d’ Astro Physique de Marseille backs up the collision theory. They studied the light signature that Phobos and Deimos emit, and came to the conclusion that both satellites are made of fine-grained dust. The composition of the surface of the moons implies that they were made up of fine grains, compacted because of the gas condensation in the outer area of the debris ring. That would also explain why the density of the moons is so small.
Previous studies found that Phobos will suffer the same fate as the former Mars’ moons, and will crash into the planet’s surface. Space.com states that the research revealed that the satellite already has stretch marks. However, the orbit of Deimos seems stable.
Source: Nature Geoscience