298 The Poetry of Physics and The Physics of Poetry
The most prominent feature of Mars is its white polar caps, which
are due to deposits of frozen carbon dioxide and water. Water has also
been found at mid-latitudes in the Martian soil through exploration of
its surface. Because of the large quantities of water found on Mars
it is possible that it harbours life or it did at one point in its existence.
Mars is tilted on its axis and, therefore, undergoes seasonal changes like
the Earth. The surface temperature on Mars varies from lows of about
−140°C during the polar winters to highs of up to 20°C in summers. The
polar caps increase during the winter and shrink in the summer. The area
between the polar caps is composed of a desert of red dust — the scene
of violent dust storms.
The surface of Mars is full of geological features boasting the highest
mountains and deepest valleys in all of the Solar System. The most
famous surface features of Mars are the Martian canals. The canals, once
thought to be the construction of an intelligent being, turns out to be only
geological features. The surface of Mars is rich in mountains, canyons
and volcanic craters. Martian volcanoes completely dwarf their terrestrial
counterparts, rising to heights of 25,000 meters and measuring 500
kilometers across.
Mars’ atmosphere is quite thin with an average atmospheric pressure
at its surface approximately 1% of that of Earth’s. The atmosphere is
95% carbon dioxide, 3% nitrogen, 1.6% argon, with traces of oxygen and
water.
Mars has two moons, Phobos and Deimos, which are small and
irregularly shaped. Phobos orbits Mars only 9,400 kilometers from
the centre of Mars orbiting the planet every 11 hours. Its mass is only
1016 kilograms or 1.8 x 10-9 Earth masses and its radius is only 11.1 km.
Deimos has a mass only 1/7th of Phobos but it is a little more than twice
the distance to the centre of Mars and orbits Mars every 30 hours.
Jupiter
Jupiter is the largest planet of the Solar System with a radius of
71,000 kilometers and more mass than all of the other planets taken
together. Its mass is 300 times that of Earth’s but still only 1/1000 the
Sun’s mass. The planet orbits the Sun at a distance of 5.2 AU once every
12 years. It rotates upon its axis once every 10 hours giving rise to a
centrifugal force resulting in its oblate spheroid shape, i.e. a bulge at its
equator and a flattening at its poles. When viewed through a telescope