Absolute Cosmos
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Absolute Cosmos

Martian moons Phobos and Deimos may have shared a common ancestor

Martian moons Phobos and Deimos are thought to be the two fragments of what was once a way larger Mars’ moon which was shattered due to a massive collision, happened sometime between one and 2.7 billion years ago. (Artist’s representation)

Phobos and Deimos, the two Martian moons are relatively small as compared to Earth’s moon.

Phobos is about twenty two kilometres in diameter and Deimos is just about twelve kilometres in dia. Both the moons were discovered in 1877 by Asaph Hall.

Their cratered surfaces and carbonaceous chondrite composition suggest that they may have been asteroids that got captured into Martian orbit. The unstable orbit of Phobos points towards the more recent capture.

But, both the moons are in almost circular orbits, near the equator, which is highly unusual for captured asteroids. The computer models have predicted that a captured asteroid should circle Mars in irregular orbit.

Scientists have also proposed that both the moons could have formed from a disk (of rock and dust) which may have circled a newborn red planet.

Despite all these efforts, their origin, however, largely remains uncertain.

Now, in yet another fresh attempt, scientists have explained a new possibility. According to the new research, both the moons may have originated from the remains of a larger moon which was once in orbit around Mars.

Between 1 and 2.7 billion years ago, this large moon collided with one stray space rock, possibly an asteroid.

This massive collision shattered the large moon into pieces, two of the pieces stayed trapped in Martian gravity and are now known as Phobos and Deimos.

In order to trace the historical orbits of the Martian moons, scientists ran computer simulations by using the latest seismic data from the NASA’s InSight lander, along with measurements and images taken from other probes currently exploring Mars and its moons.

The results showed that the orbits of Phobos and Deimos might have intersected in the past, thus indicating that the moons were likely in the same place and therefore have the same source of origin.

The data also showed that the large moon was further away from the red planet than Phobos is today.

Deimos has pretty much remained within the vicinity where it was formed. However, tidal forces are driving Phobos to slowly move towards the Mars.

Simulations also predicted the future development of Martian moons’ orbits.

Much like our only moon- which is slowly drifting away the Earth, Deimos will more likely will also move away from Mars, eventually breaking away from red planet’s gravity.

While Phobos is expected either to crash into the red planet in less than forty million years, or to be ripped apart by the gravitational forces as it approaches Mars.

For much refine calculations, scientists rely on a JAXA’s “Martian Moons Exploration” mission, which is scheduled for launch in 2024, and aims to bring back the first samples from the Phobos.

The samples will let scientists to determine the physical properties of Deimos and Phobos, i.e. how porous the Martian moons are. This in turn will help scientists to make more precise calculations about the origin of these moons.

for more details: Dynamical evidence for Phobos and Deimos as remnants of a disrupted common progenitor

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Absolute Cosmos

Absolute Cosmos

The Cosmos is all that is or ever was or ever will be…