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078

craters

OLogy Series
astronomy
card
078

craters

OLogy Series
astronomy

Craters are formed when objects from space crash onto a planet's surface. The impact blasts a hole or impression where the object lands. The size of the crater depends upon the size of the object that collides into the planet. Craters can be seen on all the rocky planets, including Earth.

The Chicxulub Crater and the Demise of the Dinosaurs
In 1987, scientists discovered one of the largest impact craters on Earth at the tip of the Yucatan Peninsula in Mexico. This giant crater, measuring more than 200 miles wide, was produced by a meteorite that blasted away rock from the Earth's crust over 65 million years ago. Scientists called it the Chicxulub Impact Crater (shik-sa-lube). After conducting research, scientists confirmed that the Chicxulub crater was created during the time of the great dinosaur extinction 65 million years ago. Many different theories exist about why this extinction occurred. Many scientists believe that a meteorite impact caused devastating changes in Earth's environment at this time and killed off lots of animals, including large, non-avian dinosaurs.

Most craters on the Moon are about:

9 miles long

900 miles long

90,000 miles long

Are you right?

Correct!

Most craters on the Moon are relatively small, although there is one crater that measures more than 200 miles wide!

More craters can be found on the Moon and Mercury than on any other planet.

Fact
or
Fiction
?

Fact

Most meteors burn up in a planet's atmosphere. Mercury and the Moon do not have an atmosphere, so more craters are visible there.

Meteorites only began hitting Earth around the time of the dinosaurs.

Fact
or
Fiction
?

Fiction

Meteorites have been hitting Earth since it formed. Most impacts happened early in Earth's history when more loose material was flying through space.

Size: a few feet to over 600 miles wide
Location: found on the surface of almost every object in the solar system
Number on Earth: about 150 that are larger than three feet wide
Characteristics: dents in planet's surface
Significance: craters provide a record of past impacts on an object's surface

Image credits: courtesy of USGS.