Download Mercury was visited by the U. S. spacecraft Mariner 10 in 1974.

Mercury was
visited by the
U. S. spacecraft
Mariner 10 in 1974.
Mercury is heavily
cratered, but not as
cratered as the
highlands of the
Moon.
There are no signs
of clouds, rivers,
dust storms, or any
other weather.
Mercury’s
gravity is 2/5
that of Earth.
(Moon was 1/6.)
Mercury has extensive
inter-crater plains.
(These are not like maria
on the Moon. The plains
are not as flat, and are
lighter in color.)
Mercury has
scarps, which are
cliffs. (These are
not found on the
Moon.)
These scarps cut
across craters,
meaning they
were formed
after the craters.
Scarps were
probably formed
by cooling and
shrinking of the
crust.
Mercury also has
“double-ringed”
craters.
The conditions that
produced these are
not known.
The Caloris Basin
is a huge crater
caused by
asteroid impact.
The opposite side of
the planet from the
Caloris Basin has
rippled, wavy surface
features called the
“Weird Terrain”.
The Weird Terrain
was formed by shock
waves from the
impact that formed
the Caloris Basin.
The daytime
temperature on
Mercury is about
700K. The nighttime
temperature is about
100K.
This 600K variation in
temperature from day
to night is the largest
of any planet or moon
in the solar system.
Mercury has a
magnetic field that
is about 100 times
weaker than
Earth’s.
The presence of a
magnetic field is
surprising since the
Moon, Venus and
Mars have no
magnetic field.
There is a question as
to whether Mercury
has the molten core
needed to cause a
magnetic field.
If there is a
molten core,
there has been no
recent geological
activity.
The ratio of core
volume to total planet
volume is greater
than for any other
object in the solar
system.
Mercury does
appear to be
deficient in
lighter rocky
material.