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Phobos, the largest moon of Mars, shows signs of being torn apart by the extreme gravitational forces exerted on it by the Red Planet, a new study shows. Researchers have revealed that unusual grooves covering Phobos’s surface, previously thought to be scars from an ancient 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 orbits Mars at a distance of 3,728 miles (6,000 km), completing a full rotation around the Red Planet three times a day, according to POT (opens in a new tab). For comparison, Earth Moon it 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.
Unlike the moon, however, Phobos’s orbit around Mars is not stable: the small satellite is caught in a death coil, slowly falling toward the Martian surface at a rate of 6 feet (1.8 meters) every 100 years, according to NASA. .
But arguably the most unusual feature of Phobos is its mysterious striped surface. Parallel grooves, or shallow striations, cover the moon. The most widely accepted theory suggests that the striations formed when an asteroid smashed into Phobos some time in the past, leaving a 6-mile (9.7 km) wide crater, known as Stickney, on the moon’s flank. .
But a new study, published Nov. 4 in the The Planetary Science Journal (opens in a new tab)suggests that the grooves may actually be the result of the moon slowly being torn apart by Mars’ intense gravity as Phobos circles ever closer to the planet’s surface.
The idea behind the new study is that as a body, in this case Phobos, gets closer to a larger body, like Mars, the smaller one will start to stretch in line with the larger body. This is known as tidal force.
In the case of Phobos, the tidal force exerted on the moon is predicted to increase as Phobos approaches the Martian surface, until eventually the tidal force is greater than the gravity holding the moon together. At that point, Phobos will completely tear apart, and the debris will likely form a small ring around the planet, like Saturn’s rings, according to the study.
While previous research has suggested that tidal forces produced Phobos’s tiger stripes, the theory has largely been dismissed due to the moon’s dusty or “fluffy” composition, which makes it too soft for such forms to form. cracks.
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In the new study, the researchers used computer simulations to test the idea that the moon’s spongy surface may rest on a somewhat cohesive subshell. A buried hard shell could have formed deep canyons into which dust from the surface could fall, creating the visible grooves in the surface, the simulation found.
“By modeling Phobos as a rubble-pile interior overlaid by a cohesive layer, we found that tidal stress could create regularly spaced parallel fissures,” the researchers wrote in the paper.
At the current rate, Phobos will complete its death spiral and collide with Mars in about 40 million years. But if tidal forces are already tearing the moon apart, then the moon could be completely destroyed much sooner, the researchers wrote.
In 2024, the Japanese Space Agency, JAXA (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 Deimos. The samples returned in 2029 should reveal what’s going on with Phobos’s streaked surface.