Puck is the largest
inner moon of Uranus, orbiting inside the orbit of Miranda. It is intermediate in size between
Portia (the second-largest inner moon) and
Miranda (the smallest of the
five major moons). Puck's orbit is located between the
rings of Uranus and Miranda. Little is known about Puck aside from its orbit, radius of about , and geometric
albedo in
visible light of approximately 0.11. Of the moons discovered by the
Voyager 2 imaging team, only Puck was discovered early enough that the probe could be programmed to image it in some detail. Images showed that Puck has a shape of a slightly
prolate spheroid (ratio between axes is 0.93–1). Its surface is heavily
cratered and is grey in color. There are three named craters on the surface of Puck, the largest being about in diameter. Observations with the
Hubble Space Telescope and large terrestrial telescopes found water-ice absorption features in the spectrum of Puck. Little is known about the internal structure of Puck. It is probably made of a mixture of
water ice and rocks, and may have been collisionally disrupted and reaccreted as a
rubble pile. The presence of a 3.0 deep 3.0 micron feature attributed to the
O-H stretching mode suggests that water ice or hydrated minerals are a common component on Puck's surface. Its surface is coated with a dark material similar to that found in the main rings. The dark material is probably made of
rocks or
radiation-processed
organics; it is possible that material spiralling inwards from Uranus's μ ring coats Puck's leading hemisphere as well. Puck, as well as the other inner satellites of Uranus, is darker than the average inner
Neptunian satellite, which could be either due to a higher level of solar irradiation at Uranus as opposed to
Neptune, or a distinct composition. The absence of craters with bright rays implies that Puck is not differentiated, meaning that ice and non-ice components have not separated from each other into a
core and
mantle.
Named features Puck has three craters named Bogle, Butz, and Lob, which are named after mischievous spirits from Scottish, German, and British folklore respectively. Details about these craters are currently unknown. == See also ==