Mars' Moons: Shattered Remnants of a Celestial Wanderer
In the vast expanse of our solar system, the origin of Mars' two diminutive moons, Phobos and Deimos, has long perplexed astronomers. Were they captured asteroids? The byproducts of a colossal impact? No existing hypothesis seems entirely satisfactory. However, a new study proposes a tantalizing idea: could these two satellites have once been a single cosmic traveler, a rogue comet cleaved in two by the gravitational might of the Red Planet?
Mars and Earth stand as the sole rocky planets in our solar system to harbor natural satellites. Yet, the comparison ends there. While our Moon boasts an impressive diameter of 3,474 kilometers, placing it among the largest moons in the solar system, Phobos and Deimos are mere specks of cosmic dust. Their dimensions range from a mere 15 to 25 kilometers, with Phobos being the larger of the two. Ironically, these minuscule moons bear names that evoke fear (Phobos) and terror (Deimos) – a stark contrast to their unassuming stature.
For decades, their diminutive size has ignited debates about their origins. It is widely accepted that they did not share the same violent birth as our Moon, which arose from a catastrophic impact on Earth. Their chemical composition and density suggest an affinity with D-type asteroids found in the outer regions of the main asteroid belt between Mars and Jupiter. Could Mars have captured these wayward space rocks as they passed nearby, much like Saturn's embrace of its moons? While plausible, no numerical simulation has succeeded in replicating this scenario, particularly the circular, near-equatorial orbits of Phobos and Deimos.
Phobos and Deimos seem to have emerged from nowhere, baffling scientists. In an effort to unravel this mystery, the Japan Aerospace Exploration Agency plans to launch the MMX (Martian Moons Exploration) mission in 2026, with the goal of collecting and returning soil samples from Phobos to Earth, offering a tantalizing opportunity to uncover the true nature of this enigmatic moon.
In the scientific context of this mission, a team of researchers studied a series of images of Phobos captured by the Mars Express probe. By analyzing the intensity of light reflected from the moon's surface, a technique known as photometry, the scientists characterized the nature of the soil. Their findings suggest that Phobos' surface is composed of a porous material akin to sand or dust. Interestingly, Phobos' reflective properties bear a striking resemblance to certain Jupiter-influenced comets, such as the celebrated 67P studied by the Rosetta probe in 2016.
Could Phobos be a captured comet, rather than an asteroid? The hypothesis is credible, even though not all photometric parameters align with this idea. Future numerical simulations may help constrain or refute this notion as we await the unfolding of the MMX mission. The results of this study have been submitted to the journal Astronomy and Astrophysics and are currently available on Arxiv.
As humanity's curiosity about the cosmos continues to deepen, the tantalizing possibility that Mars' moons are the shattered remnants of a celestial wanderer adds a captivating chapter to the ever-unfolding saga of our solar system's origins. With each new discovery, we inch closer to unraveling the mysteries that have long eluded our grasp, forever rewriting the cosmic narrative that binds us to the vast expanse of the universe.