8 of the Most Extreme Places in the Solar System [Slide Show]
A new book highlights the most unique locations in the solar system, some of which are surprisingly close to home
![8 of the Most Extreme Places in the Solar System [Slide Show]](https://www.scientificamerican.com/sciam/cache/file/2D6835B6-4710-4EA9-92BEFA018A9353A9.jpg?w=590&h=393)
8 of the Most Extreme Places in the Solar System [Slide Show]
- PERFECT FIT: A total solar eclipse is a rare event on Earth, but it is even rarer in the context of the solar system at large. Only at Earth does the interplay between the size, shape and distance of the moon and sun allow one body (the moon) to blot out the other (the sun) with virtually no overlap. The fact is even more surprising given that Earth has only one moon. Jupiter and Saturn have rich systems of several dozen satellites each, but the vast majority of moons would appear from those planets to cover only part of the sun, essentially providing a partial eclipse. At more distant Uranus and Neptune, the problem is more often the opposite—the moons blot out the entire sun and then some. Two of Saturn's moons, Prometheus and Pandora, are approximately the right size and distance to provide a total eclipse of the Earth-moon-sun variety, but both are oblong bodies that do not match the sun's shape. Luc Viatour
- MAMMOTH MOUNTAIN: Mount Everest may be the tallest mountain—and the most famous ascent—on Earth, but at 8,850 meters it is not nearly the highest peak in the solar system. That honor goes to Mars's Olympus Mons, a volcano more than 600 kilometers in diameter (about the size of Arizona) and, standing 27 kilometers at its peak, roughly three times as tall as Everest. NASA/JPL
- GAS UP: Need a pit stop? Titan is not in the most convenient location, out in orbit around Saturn, but it's got abundant hydrocarbon fuels for the taking, earning the Saturnian moon the designation "best fuel depot" from Baker and Ratcliff. Titan has a hydrocarbon cycle somewhat akin to Earth's water cycle, complete with methane rains, hydrocarbon fog and lakes of liquid methane and ethane dotting the surface, such as those photographed above by the Cassini spacecraft. NASA/JPL/USGS
- WHAT'S THAT SMELL?: Io earns the designation "stinkiest place in the solar system" in Baker and Ratcliff's book. Jupiter's third-largest moon would smell to us of rotten eggs, thanks to its active—and highly sulfurous—volcanoes. As a result, the moon's icy surface and its atmosphere are rich in pungent sulfur dioxide as well as hydrogen sulfide, which lends the characteristic offensive smell. NASA/JPL/University of Arizona (Io and inset)
- SPIN OFF: Hyperion, one of Saturn's many moons, is an odd-shaped, pockmarked object with a density so low—about half that of water—that it must be incredibly porous, essentially a 400-kilometer-long sponge. And unlike most large objects in the solar system with a well-defined rotational period, such as Earth's 24 hours, Hyperion's rotation is chaotic. If anyone lived on the tumbling, football-shaped moon, planning out one's week would be a challenge—the length of each Hyperion day varies erratically. NASA
- SHRINKY DINK: Mercury, the innermost planet, is covered by geologic landforms known as thrust scarps, a sort of stair-step feature that is produced by compression. A curving scarp is visible in the center of the photograph above. Their global distribution on Mercury implies that the entire planet has been shrinking, perhaps by as much as six kilometers in diameter over its lifetime, as its core has cooled—and the process may be ongoing. Recent observations have suggested that Earth's moon may have shrunk through a similar mechanism a relatively short time ago, only on a much smaller scale. NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
- DEVILISHLY POWERFUL: Martian dust devils earn the title of "the most extreme vacuum cleaners in the solar system" in David Baker and Todd Ratcliff's new book, The 50 Most Extreme Places in Our Solar System. Thanks to low pressure and surface gravity on Mars, the dusty vortices tower over terrestrial dust devils and tornadoes—they can reach the height of Mount Everest with winds in excess of 300 kilometers per hour, according to Baker and Ratcliff. NASA/JPL
- RETRO ACTIVE: All the planets in the solar system orbit in the same direction that the sun rotates—counterclockwise, to an observer over Earth's northern hemisphere. Likewise, all the large moons in the solar system follow prograde orbits around their respective host planets, hewing to the direction of planetary rotation, with one exception: Triton. Neptune's largest moon has a retrograde orbit: it travels in a direction opposite to the giant planet's spin. Some researchers have proposed that Triton may not have formed at Neptune but may instead be a remnant of a binary system of dwarf planets that was captured by Neptune's gravity, flinging Triton's former binary partner away in the process. The photograph above, of Neptune and Triton, came from the Voyager 2 probe, which passed the Neptunian system in 1989. NASA
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