Exploring the Composition of Mars' Moons: Phobos and Deimos

Deep space isn't just a vast expanse; it's also home to celestial bodies like the moons of Mars, Phobos and Deimos. These two moons are more than just distant rocks orbiting a red planet—they're intriguing, albeit chaotic, remnants of the solar system's early history. Let's delve into the composition and characteristics of these fascinating moons.

Overview of Phobos and Deimos

Phobos and Deimos are the two smallest and innermost natural satellites of Mars. Named after the sons of Ares (the Greek god of war) and Aphrodite (the goddess of love), they symbolize fear and terror respectively. Phobos, orbiting at an extremely close distance, completes one orbit in just under 8 hours, while Deimos takes a bit longer, completing its revolution in about 31 hours. Phobos is very close to Mars (a mere 5989 km above the surface), and Deimos is at an average distance of 23458 km from the planet.

Phobos

Phobos is the inner and larger of the two moons, with a diameter of about 22.2 km (13.8 mi). Its orbit is highly inclined and very elliptical, placing it at a mere 9,400 km above the Martian surface. Phobos is so close to Mars that it is gradually spiraling inward. This process will inevitably lead to its destruction in about 50–100 million years. The questions surrounding Phobos are many: How did it form, and where did it come from?

While many initially believed Phobos to be captured asteroids, recent evidence suggests that it might have formed in place or part of a collision with a larger parent body. However, the moons' composition provides some clues. Observations from the Mars Reconnaissance Orbiter and Mars Express have given us a clearer picture of Phobos' surface. Phobos appears to be dark and heavily cratered, with visible dust hazes due to constant bombardment by space debris. Its low density (about the same as ice, at 1.88 g/cm3) implies a porous, rubble pile-like structure, which could be due to substantial impacts throughout its history.

Deimos

Deimos is the outer and smaller of the two moons, with a diameter of approximately 12.6 km (7.8 mi). It orbits Mars at a much greater distance, taking about 31 hours to complete a single revolution. Deimos has a more typical, albeit more irregular, potato shape. Unlike Phobos, Deimos is not spiraling inward and its future is more secure, given its current orbit.

Deimos' limited size and distant position make it a less complex target for study. However, like its neighboring moon, it's composed primarily of rock and ice, mixed with a considerable amount of dust, consistent with a captured asteroid origin. Its relatively smooth surface with fewer prominent craters suggests that Deimos has experienced fewer impacts compared to Phobos. The moon's low density (about 1.47 g/cm3), similar to that of Dactyl, a moon of the asteroid Ida, indicates a porous structure and the presence of large voids within the body.

Mythological Connections

The names Phobos and Deimos come from Greek mythology, where they are sons of Ares (Mars). In Greek myth, Phobos represents fear, and Deimos symbolizes dread. This connection to the god of war Ares and Mars is by no means coincidental; these moons have long been associated with the martial realm, despite their relatively small size and non-threatening nature.

Research and Exploration

Our understanding of Phobos and Deimos continues to grow. NASA and the European Space Agency plan to send missions to both moons to study their composition and history. The Mars 2020 mission aim to gather more data on both moons, exploring potential conditions for life and understanding their geological and atmospheric processes.

While Phobos and Deimos may be small and seemingly unremarkable from a distance, they hold a treasure trove of secrets about the early solar system and the possible pathways of celestial bodies in our cosmic neighborhood.

By analyzing their composition and studying their orbits, scientists can gain valuable insights into the history of Mars and the broader context of our planetary neighborhood. Who knows what future missions and discoveries await us on these mysterious moons?