impact crater
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Clavius and other impact craters on
the Moon
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A crater formed by the high-speed impact
of a meteoroid, asteroid,
or comet with a solid surface. Craters are
a common feature on most moons (an exception is Io), asteroids, and rocky
planets, and range in size from a few cm to over 1,000 km across, in the
case a large impact basin. There is a general
morphological progression from large to small craters: large craters might
have several rings and smooth floors; intermediate craters tend to have
a central peak (formed by melting and rebounding of the crust) and smooth
floors; small craters have a simple bowl-shaped floor that is rough. Because
impact craters degrade at different rates depending on their environment,
they are valuable indicators of the age of a surface and the extent to which
resurfacing has taken place. On Earth, for example, craters are rapidly
degraded and destroyed by weathering processes; about 120 are known, with
diameters ranging from 150 m to 180 km. One of the best preserved and most
impressive is the Barringer Crater,
near Winslow in northern Arizona. On Mercury,
by contrast, which lacks an atmosphere and is geologically inert, the landscape
is peppered with craters dating back over 4 billion years.
Related categories
• CRATERS
• GEOLOGY
AND PLANETARY SCIENCE
• METEORS
AND METEORITES
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