Mercury

INTRO:

     Mercury is the closest planet to the sun. Mercury's mean distance from 
the sun is 36 million miles (57.9 million km) which is about half the 
distance from the sun to Venus. Mercury runs around the sun in a tight
little elliptical path (eccentricity of 0.2056). The Earth's own 
eccentricity is only 0.0167, much more circular than Mercury's. At it's 
closest to the Sun, Mercury is 28.6 million miles (46 million km) away.
At it's farthest it is 43.4 million miles (69.8 million km) away. Mercury
is pretty small being only 3,031 miles (57.9 km) in diameter which is 
three-eighths of Earth's diameter.

SWIFT MERCURY:

     Mercury moves faster than any other planet around the sun. Mercury 
travels 47.87 kilometers per second compared to Earth's speed 29.79 
kilometers per second. One time around the sun for Mercury is only 88 
earth-days, only about 3 months only. Astronomers up to 1965, 
thought that Mercury only rotated once in every 88 earth-days, which is 
the same time it takes to go around the sun once. That would mean that 
one side of Mercury would always face the sun. The side that would always 
face the sun be extremely hot, while the other side would be very dark and 
very cold. In 1965 they found out that Mercury rotates once every 59 
earth-days. They found out by bouncing radar beams off of Mercury. The 
signals returned from one side of Mercury were different from another side. 
They measured and analyzed the movements of the different sides of Mercury 
and found that Mercury rotated once every 59 earth-days. So Mercury did not 
have one sizzling hot side and one cold dark side. Mercury rotates on its 
axis at a tilt of about 0.1 degrees.

ABOUT THE ROCK:

     On the outside, Mercury is very much like our moon. It has little air 
or atmosphere, small, gray, reflects only 6% of the light it receives, and 
has craters, steep cliffs, and flat plains. The craters were caused by 
comets and meteorites colliding with the planet. Without a thick atmosphere 
to slow down and burn up incoming comets and meteoroids, Mercury and the moon 
are battered pieces of rock. All the lighter materials with lower boiling 
points have boiled off the surface since the creation of Mercury, because 
it is so hot leaving rocks and metal. An intriguing feature found on Mercury 
is the presence of several 3 km high cliffs as if Mercury's skin had cracked 
at some time in the past. An impact crater larger than France, called the 
Caloris Basin, was created by a shock-wave so great it created a mountain 
range on the other side of the planet. The first feature to be recorded on 
Mercury was name Crater Kuiper after Gerard Kuiper, the pioneer veteran 
planetary scientist who died while the Mariner 10 was on the way to Mercury. 

The core of Mercury is appears to be made of iron and other heavy elements. 
The Mariner 10 detected a magnetic field which indicates Mercury has a large 
iron core like the Earth. The Mariner 10 also found that Mercury has a metal 
core larger in proportion to its overall size than any other planet. This was 
suspected to be caused by the numerous catastrophic collisions that sent most 
of the planet's crust into space.

The density of Mercury is only slightly less than Earth, at 5427 kg per cube 
meter compared to Earth's density which is 5520 kg per cube meter. Scientists 
suspect that Earth and Mercury are made of similar materials, because of their 
similar densities.

CONDITIONS ON THE SURFACE:

     Since Mercury is the closest planet to the sun, it gets very hot on 
Mercury. Temperatures skyrocket to 801 Fahrenheit (427 C) and dive to 
-279 F (-173 C) at night. The sun's rays are 7 times stronger on Mercury 
and the sun seems 2 ½ times bigger in Mercury's sky. That could cause one 
bad sunburn! Mercury doesn't have enough gases to reduce the heat and light 
it receives from the sun.

      The little atmosphere that Mercury does have consists of  small amounts 
of helium, hydrogen, oxygen and sodium. Combined, the little amount of gases 
on Mercury make a possible atmospheric pressure of 0.00000000003 pounds per 
square inch (or approximately 10^-10 Pascals). Also because of the lack of 
atmosphere, the Mercurial sky is black and the stars can be seen in broad 
daylight.