Page 41 - (DK) Eyewitness - Mars

Variety of craters

Craters are classified by age, how they formed, or how they were affected by
weather. “Rampart craters’’ have circular rims pushed up by an explosive impact
and also lower, more irregularly shaped ramparts, or ridges, in the ejecta blanket
surrounding the rim. An “exhumed” crater is a crater that has been partially or
completely buried by dust or lava but later uncovered by wind or water action.
SECONDARY CRATERS EXHUMED CRATER
This crater cluster in Arabia Once buried under
Terra is over an area about rock, soil, and dust,
2 miles (3 km) wide. this “exhumed,” or
They could have been uncovered, crater
formed by the was exposed by
secondary impact of erosion. It has a
ejecta debris or by the thick mantle of
breakup of a meteor as it dust, with dark
disintegrated before streaks that show
striking Mars. where dust has SMILEY FACE
slumped down the Well-known to astronomers as
crater walls. This crater, “Happy Face,” this crater was
too, is in Arabia Terra. photographed by Mars Global
Surveyor. Named Galle Crater, it is on
Argyre Planitia, itself one of the
RAMPART CRATER A YOUNG CRATER largest Martian impact craters. The
When a meteorite slammed Termed a “fresh bluish tones are winter frost.
into Amazonis Planitia to impact crater,” this
create this rampart crater, meteorite crater in
the heat of the impact Arabia Terra
melted the layer of water shows rays of
ice, rock, and soil beneath ejecta that have MID-CRATER MOUNTAIN
the surface. Mud and not yet been worn The center of Gale Crater has risen
rocks splashed out beyond away by wind or over time to become a mountain. It
the crater’s rim and froze covered with is found in Terra Cimeria, south of
into a layered ejecta blanket sand. The dark dots Elysium Planitia and near the
with ramparts, or low ridges. are boulders from equator. A space artist pictured
ejecta debris. Gale Crater in the low light of sunset.