She's as cold as ice.

• Author: Braffman-Miller, Judith
• Position: Science & Technology - Uranus' moon 'Miranda'

IN THE SHADOWY, frigid domain of the outer planets, there is a gigantic blue-green world that is orbited by a host of small sparkling moons of ice. This huge planet, Uranus, the seventh from the sun, is surrounded by elegant, thin dark rings--and, perhaps, it even harbors a secret heart composed of diamond that is hidden deep below its heavy gaseous atmosphere.

In the dimly lit coldness of the solar system's fringes, where the sun's light is pale and weak, Uranus casts a strange, eerie greenish hue upon the chaotic jumbled ice of its frozen icy moon, Miranda. Like Frankenstein's monster, Miranda appears to have been put together from assorted parts that do not merge properly. Indeed, for years, planetary scientists have thought that this quirky, frozen little moon may have been blasted to pieces very long ago, only to take shape again--this time as a chaotic mess of icy chunks, brought back together by the relentless mg of gravity.

At last count, Uranus was circled by 27 moons--some rocky, some icy, and some both. All of Uranus' larger moons, including Miranda, are believed to consist primarily of roughly equal quantities of silicate rock and water ice. However, unlike the other main quartet of large Uranian moons, Miranda's orbit is inclined slightly. The moons of Uranus are named for characters in William Shakespeare's plays as well as from Alexander Pope's poem "The Rape of the Lock." Miranda is named for the heroine in Shakespeare's play "The Tempest."

Miranda is one-seventh as large as Earth's moon--a size that seems unlikely to support much in the way of tectonic activity. Yet, Miranda possesses one of the most varied surfaces among all terrestrial objects, including three large, odd features known as coronae, which are unique among the known bodies inhabiting the sun's family. The coronae are pockmarked lightly by cratered collections of valleys and ridges that are separated from the more heavily cratered terrain by sharply defined boundaries--much like mismatched patches sewn onto an old shirt. The more heavily cratered terrain likely is older than the more lightly cratered surface--the more heavy the cratering, the more ancient the terrain. Very young terrain is craterless, or only lightly so. Miranda's enormous fault canyons are as much as 12 times as deep as the Grand Canyon. Because of Miranda's weak gravity and large cliffs, a rock dropped off the edge of the tallest cliff would need 10 minutes to reach its foot.

Planetary...