M'hanit, known to the Federation as C/2260-Quentin, was an ancient comet that contained a massive, mostly subterranean alien structure. It was venerated and protected by the Shepherds, who saw "him" as one of the few surviving Arbiters of Life, following a divinely preordained course.
In 2259, the USS Enterprise conducted a study of C/2260-Quentin's behavior. At the time, it moved at 32.1 kilometers per second in an orbit with an aphelion of 6.4392 au, a perihelion of 0.6432 au, a period of 7.39 solar years, and an inclination of 9.613 degrees. It rotated once every 16.3 hours and had an axial tilt of 61 degrees. The comet massed 9.982 ×1012 kilograms, with a density of 0.824 grams per cubic centimeter and an albedo of 0.11. Its surface was bombarded by dangerous levels of cosmic rays.
The comet was on a collision course with Persephone III, which would have destroyed all life on the planet. The Enterprise crew's initial attempt to divert the comet with ion engines led to the discovery of the alien structure, which automatically generated deflector shields to defend the comet from perceived threats. An Enterprise away team subsequently entered the structure, where Cadet Nyota Uhura discovered that its systems responded to musical tones, described by symbols on an "egg"-shaped device in a central chamber. After deciphering the symbols, Uhura was able to deactivate the comet's shields by singing a specific melody, allowing the Enterprise to beam its team back.
Meanwhile, the Enterprise was confronted by a Shepherd ship, which demanded that they cease interfering with M'hanit. As the Enterprise was significantly outgunned by the Shepherds, the crew devised a plan to make M'hanit seem to move on its own. Captain Christopher Pike ordered the Enterprise into close proximity with the comet, using it as cover to launch Lieutenant Spock on the shuttlecraft Galileo. The Enterprise then surrendered to the Shepherds, while Spock surreptitiously set the Galileo's shields to radiate intense heat. This caused the localized sublimation of cometary material, pushing the comet into a trajectory to miss Persephone III. The Shepherds interpreted this as M'hanit's mercy and left the Enterprise in peace.
As the comet passed Persephone III, a large amount of water vapor from its surface entered the atmosphere of the planet and permanently changed its composition, increasing its rainfall levels to create more favorable conditions for plant growth and agricultural development. Uhura later found that a signal received earlier from the comet, containing the song "Vamuvamba" from Kenya, also encoded data showing its intended course through the Persephone system and a chunk of ice calved off its mass by the Galileo. It remained a mystery how the alien structure possessed foreknowledge of events hours before they occurred. (SNW: "Children of the Comet")