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Jump
to: Intro, Swift Mercury,
About the Rock, Conditions
of the Surface
INTRO:
Mercury is the closest planet to the sun.
Mercury's mean distance from the sun is 36 million miles (57.9 million
kilometer) 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.
top...
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.
top...
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 Kuiper Crater after Gerard Kuiper, the pioneer
veteran planetary scientist who died while the Mariner 10 was on the way
to Mercury.
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The very bright crater
towards the top and left on the edge of a larger older
crater is called the Kuiper Crater. |
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.
top...
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 Celsius) 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.
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