Scientists Warn Mars's Closest Moon Could Destroy Itself With Falling Debris Before Breaking Apart

The future of Mars's moon Phobos may be far more complex than previously thought, with new research suggesting it could be destroyed by its own debris before it even reaches a critical breaking point in orbit. Scientists are now re-examining how the small moon will ultimately end as it slowly moves closer to the Red Planet, reported BBC.

The two moons of Mars, Phobos and Deimos, have long puzzled scientists. One idea is that they are captured asteroids pulled into orbit by Mars's gravity. Another suggests they formed from debris created after a giant impact on the planet.

However, scientists note that their nearly circular and stable orbits make the capture theory less likely, supporting the idea that they may have formed from material around Mars after a major collision.

Phobos, the larger and closer of the two moons, orbits Mars so quickly that its orbital period is shorter than the planet's rotation. This creates tidal effects that slowly reduce its orbital energy, causing it to move gradually closer to Mars over time.

Traditionally, scientists believed that Phobos would eventually pass within the Roche limit, where Mars's tidal forces would tear it apart, forming a ring around the planet.

Researchers Harrison Agrusa and Patrick Michel from the Observatoire de la Cote d'Azur in France argue that this outcome may not be so straightforward.

They describe Phobos as an irregular, potato-shaped object that is not fully solid but instead made up of loosely held material, often described as a "rubble pile." Because of this structure, they suggest the moon may begin breaking apart much earlier than expected.

Their study used both mathematical calculations and computer simulations to model how Phobos behaves under increasing tidal stress as it moves closer to Mars.

The results from both methods show similar conclusions. If Phobos has low internal strength, its surface material may begin to break away well before reaching the Roche limit, which is about 1.6 times the radius of Mars.

This material loss is expected to happen from two opposite regions of the moon: the side facing Mars, where gravity is strongest, and the opposite side, where outward forces are highest.

The first signs of material shedding are predicted when Phobos reaches an orbital distance of about 2.25 times Mars's radius. Larger loss events may occur at 2.15 and 2.13 times the radius, followed by major destruction at around 2.09 times the radius, when large streams of material are pulled away and the moon becomes unstable.

Possible Self-Destruction Through Debris

Scientists also suggest that Phobos may be destroyed even earlier due to a process involving its own debris. Material stripped from its surface could enter orbit around Mars and later crash back into the moon at high speed.

This repeated bombardment could trigger what researchers describe as a "sesquinary catastrophe," where the moon is gradually destroyed by impacts from its own broken material, leading to its complete disintegration before it reaches the Roche limit.