Page 24 - (DK) Eyewitness - Mars

Three ages of Mars 2 Noachian Age

water
vapor from
0
Scientists believe Mars has had three major ages, or Elevation (km) -2 unfrozen soil, water, and rock evaporation
ocean
-4
time periods, each lasting many millions of years. These -6
ages are named for different geographic areas of Mars.
The earliest period, the Noachian Age, may have been -8 basement rock
warm and wet, with active volcanoes. The Noachian -90 -60 -30 Latitude 30 60 90
0
Age corresponds with Noachis Terra, in the south of
Mars, where the ancient uplands have been battered by condensation on polar cap Early Hesperian Age
meteorites. Next is the Hesperian Age, which became 2 polar layered deposits frozen water
steadily colder, with water freezing. This age is named 0 meltwater soil, vapor from
sublimation
ice, and
for the southern hemisphere’s Hesperia Planum, which -2 unfrozen soil, water, and rock rock
is considered younger because it shows less cratering. Elevation (km) -4
The present era is the Amazonian Age, named for the -6
flat, low Amazonis Planitia of the north. This is a dusty -8 basement rock meltwater
desert region with relatively few craters and is one of -90 -60 -30 0 30 60 90
the youngest on Mars. Latitude
frozen soil, ice, Late Hesperian Age
2 and rock
Noachian Mars 0 catastrophic floods
The Noachian era probably Elevation (km) -2
began about 4.5 billion years -4
ago when Mars was formed ground water trapped
and ended roughly 3.5 billion -6 under high pressure
years ago. During this period -8 basement rock
meteorite cratering was
slowing down. A warmer -90 -60 -30 0 30 60 90
climate may have permitted Latitude
rivers, lakes, and even oceans
to exist on the surface. WATER INTO ICE
In the Noachian Age (top), liquid
water may have been present on
the planet’s surface and also
underground. By the early Hesperian
WATER IN ABUNDANCE Age (middle), most water had seeped
Some scientists believe that the low underground or was frozen on the
plains of Mars’s north polar regions surface. By the late Hesperian Age
MUCH AS IT WAS 3.5 BILLION YEARS AGO might have been flooded by water (bottom), much of the planet’s water
A artist’s panoramic view of Arabia Terra flowing from the southern highlands was locked up in underground ice
shows Schiaparelli Crater in the foreground. in Noachian and Hesperian times. A deposits, but pockets of pressurized
The area has changed little from Noachian thicker atmosphere could have held liquid water occasionally erupted on
times when meteorites were still raining enough water vapor to produce rain. the surface to produce local
down on the planet's surface. breakouts or massive floods.