Moons are enchanting, mesmerizing objects dwelling in their orbits around planets both within and beyond our Solar System. Earth’s own large Moon, a silver-golden world that shines in our starlit night sky with the reflected fires of our Star, the Sun, has long been the inspiration of haunting poems and tales of love, as well as myths of magic and madness. Most of the moons of our Sun’s own bewitching family are glistening little icy worlds in orbit around the giant planets of the outer Solar System. In June 2013, astronomers announced their dedicated hunt for a habitable moon-world beyond our Sun’s family, circling around the planet Kepler-22b, that dwells in the faraway family of a different star.
Moons can be found in a rich assortment of various sizes, shapes, and types. Although they are generally solid little worlds, a few of them are known to sport atmospheres. Indeed, the atmosphere of the second largest moon in our Solar System, Titan of Saturn, is so dense that it hides Titan’s strange hydrocarbon-slashed surface beneath a thick orange veil.
Most of the moons dwelling in our Sun’s family were probably born from primordial disks of dust and gas, orbiting around newly formed planets, when our Solar System was very young about 4.5 billion years ago. There are at least 150 moons circling the planets in our Solar System–and about 25 moons are currently awaiting official confirmation of their discovery.
Of the four terrestrial, rocky planets of the inner Solar System (Mercury, Venus, our Earth, and Mars), both Mercury and Venus are moonless. Earth possesses one lone Moon, but it is a very large one–the fifth largest moon in our entire Solar System, in fact. Mars, on the other hand, has two tiny misshapen moons that resemble rocky potatoes, and are lumpy and dark, as they travel in their nearly circular orbits close to the plane of the Martian equator. The Martian moons, Phobos and Deimos, are probably asteroids that were captured by Mars long ago.
The outer Solar System is more richly endowed with moons than the inner regions. The two enormous gas giant planets, Jupiter and Saturn, and the ice giant planets, Uranus and Neptune, have numerous moons of various sizes, shapes, and origins. As these enormous planets grew, during the early days of our Solar System, they were able to ensnare wandering objects with their mighty gravitational grips.