Origin
The origin of the Martian moons is still controversial. The main hypotheses are that they formed either by capture or by accretion. Because of the similarity to the composition of C- or D-type asteroids, one hypothesis is that the moons may be objects captured into Martian orbit from the asteroid belt, with orbits that have been circularized either by atmospheric drag or tidal forces, as capture requires dissipation of energy. The current Mars atmosphere is too thin to capture a Phobos-sized object by atmospheric braking. Geoffrey Landis has pointed out that the capture could have occurred if the original body was a binary asteroid that separated due to tidal forces. The main alternative hypothesis is that the moons accreted in the present position. Another hypothesis is that Mars was once surrounded by many Phobos- and Deimos-sized bodies, perhaps ejected into orbit around it by a collision with a planetesimal.
Read more about this topic: Deimos (moon)
Famous quotes containing the word origin:
“The essence of morality is a questioning about morality; and the decisive move of human life is to use ceaselessly all light to look for the origin of the opposition between good and evil.”
—Georges Bataille (1897–1962)
“Someone had literally run to earth
In an old cellar hole in a byroad
The origin of all the family there.
Thence they were sprung, so numerous a tribe
That now not all the houses left in town
Made shift to shelter them without the help
Of here and there a tent in grove and orchard.”
—Robert Frost (1874–1963)
“Good resolutions are useless attempts to interfere with scientific laws. Their origin is pure vanity. Their result is absolutely nil. They give us, now and then, some of those luxurious sterile emotions that have a certain charm for the weak.... They are simply cheques that men draw on a bank where they have no account.”
—Oscar Wilde (1854–1900)