The Hot Planet
Mercury is the planet closest to the Sun. It is also very small –
about the size of Earth’s moon. It is named after the Roman
messenger god because it moves very quickly.
Quick Q’s:
1. How long does
Mercury take to orbit
the Sun?
Like all planets,
Mercury goes around
the Sun in an elliptical
(oval) orbit. It takes
about 88 days to
complete one orbit.
2. How long is a day
on Mercury?
Mercury goes around
the Sun very fast, but
rotates very slowly on
its axis. Therefore a day
on Mercury is equal to
176 Earth days!
3. Why does Mercury
have huge craters?
As Mercury has very
little atmosphere,
meteors do not burn
up in the air. Instead,
they fall on the surface,
creating huge craters.
4. What colour is the
sky above Mercury?
If you were to look at
the sky from Mercury,
even during the day, it
would appear black.
This is because there is
no atmosphere to
spread the Sun’s light.
5. Which is the largest
crater on Mercury?
The largest crater is
the Caloris Basin. It is
about 1,300 kilometres
(808 miles) in
diameter. It is also one
of the biggest craters in
the solar system.
Q Why are nights on Mercury freezing cold,
although it’s the planet closest to the Sun?
A Unlike Earth, Mercury is not
surrounded by a thick protective blanket
of air called the atmosphere. This means
that the heat from the Sun escapes, leaving
the planet freezing at night. While the
temperature during the day can be as
high as 467 °C (873 °F), at night it drops
to -183 °C (-297 °F).
Q What is the surface of Mercury like?
A If you were to land on mercury, you
would find a surface very similar to that of
the Moon. It has dust-covered hills, cliffs and
is dotted by craters. The planet also has a
thick metallic core and
a sandy crust.
Q What space probes have been launched
to Mercury?
A Mercury, being so close to the Sun, is
very difficult to explore. Space probes are
unable to withstand the heat of the planet.
Only one space probe, Mariner 10, has visited
Mercury so far. It photographed nearly half
of the planet’s surface. A new probe,
Messenger, is on its way to Mercury.
It was launched on 3 August 2004
and is expected to return, after
photographing the whole planet,
in March 2012. Another space mission
will begin in 2013.
Mercury close-up
From up close, the surface of Mercury can be
seen to be pitted with huge craters.
Any meteor that comes near Mercury falls
on the surface and creates a crater, as there
is no atmosphere to burn the meteor up.
Looking at Mercury
The Mariner 10
space probe is the
only one to
have got
anywhere
near Mercury so
far. It is sending
photographs of the
surface of Mercury
regularly now.
Sandy surface
Mercury has a surface that is full of hills and steep
canyons, all of it covered with a mixture of sandy
substances. The core of the planet is metallic, like all
the rocky planets.
solar panel
TV cameras
Sun shade
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