Perhaps Mars is slowly ripping apart its largest moon

A new study shows that Mars’ largest moon, Phobos, has been torn apart by extreme gravitational forces acting on it from the Red Planet.

The researchers discovered an unusual coating of grooves Phobossurfaces previously thought to be scars from antiquity asteroid impact, are actually dust-filled canyons that widen as the moon is stretched by gravitational forces.

Phobos is about 17 miles (27 kilometers) across at its widest point and orbit Mars at a distance of 3,728 miles (6,000 km), making a complete revolution around the Red Planet three times each day, in accordance with NASA (opens in a new tab). For comparison, Earth month is about 2,159 miles (3,475 km) wide, 238,855 miles (384,400 km) from our planet, and takes about 27 days to complete one orbit.

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However, unlike the Moon, Phobos’ orbit around Mars is unstable: the tiny moon is trapped in a death spiral and slowly falls toward the Martian surface at a rate of 6 feet (1.8 meters) every 100 years, according to NASA. .

But the most unusual feature of Phobos is its mysterious striped surface. Parallel grooves, or surface lines, cover the moon. The most widely accepted theory suggests that the streaks were formed when an asteroid slammed into Phobos at some point in the past, leaving behind a 6-mile-wide (9.7 km) crater known as Stickney on the moon’s flank.

But a new study published on November 4 in Planetary Science Journal (opens in a new tab)suggests that the grooves may actually be the result of the moon being slowly torn apart by Mars’ intense gravity as Phobos orbits ever closer to the planet’s surface.

The idea behind the new research is that when one body, in this case Phobos, approaches a larger body, such as Mars, the smaller one will begin to pull in line with the larger body. This is known as tidal force.

In the case of Phobos, the tidal force acting on the Moon is predicted to increase as Phobos approaches the surface of Mars, until finally the tidal force becomes greater than the force of gravity holding the moon together. At that point, Phobos will be completely torn apart, and the debris will likely form a tiny ring around the planet, like the rings of saturnaccording to the study.

While previous studies suggested that tidal forces create Phobos’ tiger stripes, the theory has been largely dismissed because of the moon’s powdery or “fluffy” composition, which makes it too soft to form such cracks.

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In a new study, researchers used computer simulations to test the idea that the moon’s fluffy surface may lie on top of a somewhat cohesive sublayer. The buried hard shell could potentially have formed deep canyons into which surface dust could have entered, creating the grooves visible on the surface, the simulations showed.

“By modeling Phobos as an internal rubble pile covered by a cohesive layer, we found that tidal deformation can create regularly spaced parallel cracks,” the researchers wrote in the paper.

At its current speed, Phobos will complete its death spiral and crash into Mars in about 40 million years. But if tidal forces are already ripping the Moon apart, the satellite may be completely destroyed long before that, the researchers write.

In 2024, the Japan Space Agency, JACKS (opens in a new tab), will launch a new mission known as the Martian Moons eXploration (MMX) to land a spacecraft on both Phobos and Deimas. Samples returned in 2029 should show what is happening to Phobos’ streaked surface.