THE SOLAR SYSTEM
Mars from Viking 2.
This photo of Mars was
taken by Viking 2 from
419,000 km (260,000 miles)
away as the spacecraft
approached the planet
on 5 August 1976. Viking 2
was preceded to Mars by
Viking 1. In this view of the
crescent-lit planet, contrast
and colour ratios have
been enhanced to improve
visibility of subtle surface
topography and colour
variations. Water-cloud
plumes extend north-west
from the western flank
of Ascraeus Mons,
northernmost of the three
great volcanoes that line
Tharsis Ridge. The middle
volcano, Pavonis Mons,
is just visible on the dawn
terminator, below and west
of Ascraeus Mons. Valles
Marineris, the great system
of rift canyons, extends
from the centre of the picture
at the terminator downwards
to the east. Including the
huge complex at its west and
named Noctis Labyrinthus,
Valles Marineris stretches
nearly 4800 km (3000 miles).
The bright basin near the
bottom of the photo is
the Argyre Basin, one
of the largest basins on
Mars. The ancient crater
lies near the south pole
(not visible in this photo)
and is brightened by the
icy frosts and fogs that lie
in the bottom of the basin
and are characteristic of
the near-polar regions of
Mars when each pole is
experiencing its winter
season.C Atl of Univ Phil'03stp 2/4/03 3:04 pm Page 79