Page 42 - Curriculum Visions Dynamic Book

Within this atmosphere there are dense clouds that appear brown and permanently obscure the solid surface of the moon—perhaps as a result of the reaction of sunlight with particles containing carbon or nitrogen, producing a natural photochemical smog.
Mimas
This moon has a highly cratered surface. It includes the Herschel Crater, which is 130 km across and is proportionally one of the largest craters of any body in the solar system.
Normally, impacts to produce craters of this size would have brought about the disintegration of the moon, so it is not clear what saved Mimas from destruction.
Phoebe
Space probe Cassini has shown that Phoebe’s surface is made of water-ice, water-bearing minerals, carbon dioxide, and primitive organic chemicals in patches on the surface.
Enceladus
This moon is very reflective and looks white. It also seems to have been geologically active and may have volcanoes (see bottom picture on pages 6–7).
Teths
This is a large but geologically inactive moon. It has a heavily cratered surface of low relief, which shows no signs of having changed since early in the history of the solar system. It may be a mixture of rock and ice, which would have allowed crater rims to have slumped down, rather than staying elevated as they are on the Earth’s Moon.
Dione
This is another moon showing signs that it may have been geologically active. Its cratered surface is split by fissures, and some plains appear to have been resurfaced by lava.
Iapetus
This is a strange moon—half dark, half light. The light half appears to be icy, but the cause of the dark surface is unknown.
 The moon Titan, enveloped in perpetual cloud.
 The moon Mimas, with its extraordinary Herschel Crater.
crater A deep bowl-shaped depression in the surface of a body formed by the high-speed impact of another, smaller body.
lava Hot, melted rock from a volcano.
photochemical smog A hazy atmosphere, often brown, resulting from the reaction of nitrogen gases with sunlight.
plain A flat or gently rolling part of a landscape.
reflective To bounce back any light that falls on a surface.
volcano A mound or mountain that is formed from ash or lava.
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