How Mars is tearing apart its own moon
Mars and its moon Phobos are far closer together than Earth and its moon, causing a strong gravitational pull that will eventually tear the moon apart.
The Curiosity rover observes the moon Phobos grazing the sun's disk on Martian day, or sol, 37 (September 13, 2012) in this NASA handout image.
NASA/Reuters
NASA confirmed Tuesday that Mars鈥檚 moon Phobos is showing early signs of structural failure that will likely .
Visible grooves on Phobos are caused by gravitational tidal forces as Mars and Phobos mutually pull on one another, just as Earth and our moon pull on each other.聽
鈥淲e think that and the first sign of this failure is the production of these grooves,鈥� Dr. Terry Hurford, a researcher with NASA鈥檚 Goddard Space Flight Center, said in a press release.
Phobos, one of the Red Planet's two moons,聽orbits only 3,700 miles above Mars, making it the closest planet-moon relationship of any planet in our solar system. By comparison, our moon orbits about聽聽above Earth.聽And, while Earth's moon is inching away from our planet, Phobos is moving closer: Mars continues to pull in its moon at a rate of about 6.6 feet per century.
But fortunately for Phobos, scientists predict the moon has about 30 to 50 million more years before it is completely pulled apart.
Scientists were already aware of Phobos鈥� grooves and cracks, but until now they believed these 鈥渟tretch marks鈥� were caused by the impact from the Stickney crater. The crater is , which is almost half of the irregularly shaped moon's overall average diameter, so until now it seemed like an obvious cause for the cracks.
Further analysis of the moon鈥檚 cracks found that they do not radiate outward from the Stickney crater, but instead . As another source of evidence against the Stickney theory, some of the grooves are younger than others, 鈥渨hich would be the case if 鈥� and not a single, forceful impact. 聽聽聽
Scientists have also revised their thinking regarding the consistency of Phobos鈥� interior. Previously thought to be solid, scientists have recently agreed that the interior of Mars鈥� moon is likely a rubble pile, barely held together by a 330-foot layer of powder. Scientists associated with the study changed their way of thinking because even the strong tidal forces between Phobos and Mars were 鈥渢oo weak to fracture a solid moon of that size.鈥�
鈥淭he funny thing about the result is that it shows Phobos has ,鈥� Dr. Erik Asphaug, a professor of planetary science at the University of Arizona and co-investigator of the study said in a NASA press release. 鈥淭his makes sense when you think about powdery materials in microgravity, but it鈥檚 quite non-intuitive.鈥�
Not only is Phobos closer to its planet than Earth鈥檚 moon, but it also has a faster orbit. Phobos revolves around Mars up to , rising in the west and setting in the east.聽