Our first planet to study is Mercury, the planet closest to the
Sun. Mercury is a rocky planet, which for many years was thought to be free
from water. However, Muggle scientists recently discovered ice towards the
Northern Pole of Mercury, which is shielded from the Sun's heat by shadows from
the craters, and this is possibly caused by water. Mercury is very much like
the moon of Planet Earth in that it is completely covered in craters, the
largest one being the Caloris Basin. That one probably came from a crash of
some sort  years and years ago.

Speaking of the heat, Mercury is capable of being a very hot planet
sometimes. It has temperatures ranging from 90K to 700K. Recently, volcanic
activity has been confirmed on Mercury for many years ago, but it is no longer
actively volcanic.

Mercury is named for the Roman god of thievery, commerce, and travel. His
Greek counterpart, Hermes,was the messenger of the gods, so that suggests
speed. It is an appropriate name because Mercury is a fast planet, moving quite
quickly about the Sun. That might have something to do with the fact that it
has the smallest orbit to go, but who is really comparing that? It is also
one of the easier planets to see in the night sky - in fact, it is so easy you
can see it without a telescope!

Not too much is known about Mercury, as it can be tricky to research it from
Earth.

Reaching Mercury from Earth poses significant technical challenges, because
the planet orbits so much closer to the Sun than Earth. A Mercury-bound
spacecraft launched from Earth must travel over 91 million kilometers into the
Sun's gravitational potential well. Mercury has an orbital speed of 48 km/s,
whereas Earth's orbital speed is 30 km/s. Thus the spacecraft must make a
large change in velocity (delta-v) to enter a Hohmann transfer orbit that
passes near Mercury, as compared to the delta-v required for other planetary
missions.

The potential energy liberated by moving down the Sun's potential well
becomes kinetic energy; requiring another large delta-v change to do anything
other than rapidly pass by Mercury. To land safely or enter a stable orbit the
spacecraft would rely entirely on rocket motors. Aerobraking is ruled out
because the planet has very little atmosphere. A trip to Mercury requires more
rocket fuel than that required to escape the Solar System completely. As a
result, only two space probes have visited the planet so far.A
proposed alternative approach would use a solar sail to attain a
Mercury-synchronous orbit around the Sun.