The grooves on Phobos are a sign of the moon’s demise according to new research establishing the grooves’ nature.
When looking at images of Phobos, one of two satellites orbiting Mars, one of the most evident trait is the grooves stretching on the moon’s surface. These parallel marks initially thought to be the result of impact with debris in time are in fact a result of tidal forces.
According to the scientists involved in the new study, the grooves on Phobos are a sign of the moon’s demise, leading slowly to structural failure. Terry Hurford with NASA’s Goddard Space Flight Center stated that Phobos is already starting to fail structurally, with the parallel grooves standing as a stark reminder of this fact.
Phobos orbits only 3,700 miles above Mars, being the moon with the closest orbit to a planet in the entire solar system. Due to this close orbit, Mars’s gravity is pulling the moon in closer, while contributing to its structural failure. Mars completes one rotation on its axis in approximately 25 hours. Phobos completes one orbit around the red planet in 7.5 hours. Phobos is estimated to fail structurally in 30 to 50 million years.
With three rotations around Mars in just one martian day and a strong gravity pull, Phobos is drawn closer to Mars at a rate of 6.6 feet/100 years. When the orbit of Phobos reaches the Roche Limit where tidal forces become strongly opposing, this is the moment when Phobos will reach the point of full structural failure.
According to the scientific team presenting the results of their study at the Meeting of the Division of Planetary Sciences of the American Astronomical Society, the interior of Phobos is also a factor playing an important role in the moon’s demise.
With a dispersed interior that looks much like a pile of debris, tidal forces acting on the poles of the moon will not find any obstacle in destroying Phobos. The interior of the moon is only protected by powdery regolith dispersed as a blanket of 330 feet in thickness.
When all these are factored in with computer modelling, the scientific team discovered that the grooves marking the surface of Phobos are signs of tidal forces at work. While previously thought to be the marks of impact, the new modelling showed that their location is consistent with the idea that tidal forces are slowly acting in pulling the moon of Mars apart. Some grooves are older, while some have been found to be younger. According to the scientific team this is a clear indication that the process is ongoing.
Phobos may not be the only moon in this situation. Triton, of the moon orbiting Neptune may suffer the same fate, with its surface being marked in a similar manner.
Photo Credits: Wikimedia