The weirdest moons in the solar system
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Loading... - Cheryl Gilbert
- 24 Oct 2022
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All but two of our solar system's planets have natural satellites of one sort or another. Earth's own moon, a beautiful but stark, dead world shaped by ancient volcanoes and countless impact craters, is undoubtedly the most familiar, but it's far from being the most interesting. Each of the outer solar system's giant planets is accompanied by a large retinue of satellites, many of which formed at the same time and from the same ice-rich material as the planets that host them. Although far from the sun and starved of solar heat and light, they nevertheless show as much variety as the planets themselves.
Here, we take a trip to visit some of the strangest and most exciting of these astonishing worlds. Some, such as Jupiter's Callisto and Saturn's Mimas, have been frozen solid for billions of years, but bear extraordinary scars from exposure to bombardment from space. Others, such as Saturn's shepherd moons Pan and Atlas and Neptune's lonely Nereid, have been affected throughout their history by interactions with their neighbors. Most excitingly, some of these exotic worlds have been heated by powerful tidal forces from their parent planets, triggering phases of violent activity like those which shaped Miranda, Uranus' Frankenstein moon. In some cases these forces are still at work today, creating fascinating bodies such as Jupiter's tortured Io and Saturn's icy Enceladus, whose placid exterior may even hide the greatest secret in the solar system: Extraterrestrial life itself.
Callisto
The outermost of Jupiter's Galilean moons, Callisto is the third-largest moon in the solar system, and is only slightly smaller than Mercury. Its main claim to fame is the title of most heavily cratered object in the solar system; its dark surface is covered in craters down to the limit of visibility, the deepest of which have exposed fresh ice from beneath and scattered bright 'ejecta' debris across the surface.
Callisto owes its cratered surface to its location in the Jupiter system — the giant planet's gravity exerts a powerful influence, disrupting the orbits of passing comets and often pulling them to their doom, most spectacularly demonstrated in the 1994 impact of Comet Shoemaker-Levy 9.
Jupiter's larger moons are directly in the firing line, and end up soaking up more than their fair share of impacts, but Callisto's inner neighbors — influenced by greater tidal forces — have all experienced geological processes that wiped away most of their ancient craters. Callisto's surface, however, has remained essentially unchanged for more than 4.5 billion years, developing its dense landscape of overlapping craters across aeons. Read More…
