Tallest, deepest, hottest, weirdest: Our solar system is a place of extremes. In a new book, The 50 Most Extreme Places in Our Solar System
, authors David Baker and Todd Ratcliff take readers on a sightseeing tour of gas giants, icy moons, and the heat-blasted inner planets. Here we present a sampling of our favorite extraordinary locales. WEIRDEST ROTATION
The Saturnian moon Hyperion
is a lumpy thing, measuring about 255 x 163 x 137 miles in diameter along its three axes. Since moons of this size typically have enough gravity to pull them into a spherical shape, astronomers suggest that it may be a fragment of a larger moon that was shattered by an impact. The planet's odd shape explains why the planet is, as Baker and Ratcliff put it, "a tumbling chaotic mess." Most large moons are tidally locked, meaning that the same face of the moon always faces its planet. But Hyperion's bizarre shape prevents such locking, because the gravitational torques from Saturn and the moon Titan tug at it unevenly.
The result: A rotation that's impossible to predict. "The days are never the same," the authors write. "Not only does the rotation rate (the length of day) vary erratically, but Hyperion's north pole continually points to a different location in space." Astronomers know the equation to predict the moon's rotational motion, but small uncertainties in measurements of the moon's initial location or velocity turn into large uncertainties over time. For Hyperion, the authors say, "it is completely impossible to predict the direction of its spin axis after about 300 days--it could be pointed anywhere!"