Introduction
Mercury is the first planet in the solar system and is the planet closest to the
sun. It is a very small planet. Mercury probably got his name because it was the
fastest planet in the sky. In Roman Mythology, Mercury was the god of travel,
commerce and thievery. In Greek mythology Mercury was the messenger god. Mercury
has been known for a very long time, from around 3000 BC. The Greeks gave
Mercury two names: Apollo when it appeared as the morning star and Hermes when
it appeared as the evening star.
^^Back
to top^^
Fact File
Distance from the sun: approx. 57,910,000 km
Diameter: 4,880 km
Mass: 3.3023 kg
Temperature range: 90K - 700K
^^Back
to top^^
Missions to Mercury
Only one spacecraft has gone to Mercury. This spacecraft is the Mariner 10. It
took very few pictures even after going past Mercury 3 times between 1974 and
1975. It managed to cover up only 45% percent of the planet. NASA launched
another spacecraft to Mercury again in 2004 called the Messenger. It will go
past Mercury many times. Later in 2011 it will start orbiting Mercury.
^^Back
to top^^
Orbit of Mercury
Mercury does not revolve around the sun in a proper circle. In other words it’s
orbit is eccentric. At one point it is barely 46 million kilometers from the sun
while at another point it is close to 70 million kilometers from the sun. This
explains why the distance from the sun that is mentioned above is an average
value. Unlike Earth which has 365 days in a year Mercury has only 3 days in 2
years. Therefore one year would have an average of only 1½ days. This was known
only in 1965. Until then it was thought that the length of one day on Mercury
was the same as the length of one year on Mercury.
^^Back
to top^^
Core, Crust and Crater
Mercury’s surface is heavily cratered. It looks very much like our moon. The
planet has a very large iron core taking up a great amount of the mass. The core
has a diameter ranging from 3600 to 3800 km, so you can imagine how large it is.
This leaves the planet with a thin mantle and crust made out of silicate just
like Earth’s except that the mantle is only 600 km and the crust is 100-200 km
thick, much smaller than Earth's.
In the centre of the planet is a large iron core taking up an estimated 42% of
the planet's volume. Mercury is thought to have the highest iron content
compared to any other planet in the solar system. (3600-3800km)
Surrounding the core is a 600 km layer of mantle, made up of silicates, which is
similar to the Earth's, except that the Earth's layer of mantle is much larger.
Mercury's crust is thought to be 100-200 km thick. A prominent feature of this
layer is the many ridges, that stretch over several hundred km. This is thought
to have formed after the core and mantle cooled and contracted after the crust
solidified.
^^Back
to top^^
Atmosphere and Surface
Unlike Earth which has a constant and stable atmosphere, Mercury has an
atmosphere which is constantly escaping and being created again. The atmosphere
is being created by solar wind taking off particles from Mercury. They keep
escaping because of Mercury’s high temperature. A vast amount of Mercury’s
surface is covered by sloping hills. These hills can be unbelievable in size.
Some of them are even hundreds of kilometres in size and upto three kilometres
in height. The most noticible feature of landscape on Mercury is the Caloris
Basin.
The Caloris Basin is extremely
large, about 1300 km in diameter and was probably created by a huge asteroid
smashing the surface of Mercury. On the exact opposite side of the planet the
crater has left a strange region unlike the rest of the planet
^^Back
to top^^
Did You Know?
1.Recent radar observations show that the north pole of mercury contains water.
2.Despite its tiny size, Mercury has a magnetic field, but its as tiny as the
planet being only 1% of Earth’s.
3.Despite its tiny size, Mercury has a magnetic field, but its as tiny as the
planet being only 1% of Earth’s.
4.Despite its tiny size, Mercury has a magnetic field, but its as tiny as the
planet being only 1% of Earth’s.
