Mercury Report

Mercury Report

The magnificent planet Mercury is the planet I have chosen to research. In
this report I have explained all there is to know about Mercury.

The Romans gave Mercury its name after the fleet-footed messenger of the
gods, because it seemed to move quicker than any other planet. It is the closest
planet to the Sun, and second smallest planet in the solar system. Its diameter
is 40% smaller than Earth, and 40% larger than the Moon. It is even smaller than
Jupiter\'s moon Ganymede, and Saturn\'s moon Titan.

Mercury\'s history of formation is similar to that of Earth\'s, which happened
about 4.5 billion years ago. It has a dense metallic core, and a silicate crust.
Its surface is no longer active and remains the same as it has for millions of
years. Plains cover the majority of Mercury’s surface. Much of it is old and
heavily cratered, but some of the plains are less heavily cratered. Scientists
have classified these plains as intercrater plains, and smooth plains.
Intercrater plains are less saturated with craters, and were probably formed as
lava flows buried the older terrain. The smooth plains are younger still with
fewer craters. They can be found around the largest crater on Mercury, the
Caloris basin. The Caloris basin is 1,300 kilometers in diameter, and was
probably caused by a projectile larger than 100 kilometers in size. The impact
produced concentric mountain rings three kilometers high and sent ejecta 600 to
800 kilometers across the planet.

Like our Moon, Mercury has almost no atmosphere, mostly burned off millions
of years ago by the planet\'s close proximity to the Sun. What little atmosphere
exists is composed chiefly of argon, neon and helium. With no atmosphere to
protect the surface, there has been no erosion from wind or water, and
meteorites do not burn up due to friction as they do in other planetary
atmospheres. Mercury\'s surface is also very much like Earth\'s Moon, scarred by
thousands of impact craters resulting from collisions with meteors. While there
are areas of smooth terrain, there are also cliffs, some soaring up to two miles
high.

Most of the scientific findings about Mercury came from the Mariner 10
spacecraft, which was launched on November 3, 1973. It flew past the planet on
March 29, 1974 at a distance of 705 kilometers from the surface. On September
21, 1974 it flew past Mercury for the second time and on March 16, 1975 for the
third time. During these visits, over 2,700 pictures were taken, covering 45% of
Mercury\'s surface.

Until Mariner 10, little was known about Mercury because of the difficulty in
observing it from Earth telescopes. At maximum elongation it is only 28 degrees
from the Sun as seen from Earth. Because of this, it can only be viewed during
daylight hours or just prior to sunrise or after sunset. When observed at dawn
or dusk, Mercury is so low on the horizon that the light must pass through 10
times the amount of Earth\'s atmosphere than it would if Mercury was directly
overhead. After close observation by the Mariner 10 spacecraft, the period was
determined to be 58.646 +- 0.005 days. Mercury’s rotational period is 88 earth
days.

Mercury is not tidally locked to the Sun; its rotational period is tidally
coupled to its orbital period. A day on Mercury is 176 Earth days long. Mercury
has no evident satellites or rings, because it exists so close to our scorching
sun. Mercury’s mean distance from the sun is 58 million kilometers (about 36
million miles). Mercury’s diameter is 4875 km (3030 miles). Mercury’s volume
and mass are about 1/8 that of Earth, while its gravitational pull is .38 of
Earth. Mercury\'s density is 5.5 g/cm3 where Earth\'s is only 4.0 g/cm3. This high
density indicates that the planet is 60 to 70 percent by weight metal, and 30
percent by weight silicate. This gives a core radius of 75% of the planet radius
and a core volume of 42% of the planet\'s volume.

Scientists did not believe Mercury would have a magnetic field, due to the
small size of it. The presence of a magnetic field indicates that a planet has
an iron core that is at least partially molten. Magnetic fields are generated
from the rotation of a conductive molten core and are known as the dynamo
effect. Mariner 10 showed that Mercury has a magnetic field that is 1% as strong
as Earth\'s. This magnetic field is inclined 7 degrees to Mercury\'s axis of
rotation and produces a magnetosphere around the planet.

Mercury is the closet planet to the sun and without