The Moon
(TFS)- The moon is the natural satellite of the earth.
Located at 384,000 km, it is the star closest to our planet that is why it
appears enormous to our naked eye. In reality, the moon is four Times smaller
than the earth. Thanks to the probes sent
since 1959 and the space missions begun in 1969, we managed to know the nature
of its soil.
On its surface, mountains rise to more than 8,000 m, there are also plains and huge craters dug by the fall of meteorites for billions of years.
The rotation of the Earth and the moon around the sun causes movements of water masses.
On its surface, mountains rise to more than 8,000 m, there are also plains and huge craters dug by the fall of meteorites for billions of years.
The rotation of the Earth and the moon around the sun causes movements of water masses.
The Moon is the only natural satellite of Earth:
The Moon Profile
diameter: 3476 km
mass: 7.35e22 kg
Due to its size and composition, the Moon is sometimes
classified as a terrestrial "planet" along with Mercury, Venus, Earth
and Mars.
First Encounter
The Moon was first visited by the Soviet spacecraft Luna 2 in
1959. It is the only extraterrestrial body to have been visited by humans. The
first landing was on July 20, 1969; the last was in December 1972. The Moon is
also the only body from which samples have been returned to Earth. In the
summer of 1994, the Moon was very extensively mapped by the little spacecraft Clementine and
again in 1999 by Lunar Prospector.
Apollo 11
Apollo 11 was the spaceflight that landed the first two
humans on the Moon. Mission commander Neil Armstrong and
pilot Buzz Aldrin, both
American, landed the lunar module Eagle on July 20, 1969, at 20:18 UTC.
Armstrong became the first to step onto the lunar surface six hours later on
July 21 at 02:56:15 UTC; Aldrin joined him about 20 minutes later. They spent
about two and a quarter hours together outside the spacecraft, and collected
47.5 pounds (21.5 kg) of lunar material to bring back to Earth. Michael Collins
piloted the command module Columbia alone in lunar orbit while they were on the
Moon's surface. Armstrong and Aldrin spent just under a day on the lunar
surface before rendezvousing with Columbia in lunar orbit.
Effects
on Earth
The gravitational forces between the Earth and the
Moon cause some interesting effects. The most obvious is the tides. The Moon's gravitational attraction is stronger on
the side of the Earth nearest to the Moon and weaker on the opposite side.
Since the Earth, and particularly the oceans, is not perfectly rigid it is
stretched out along the line toward the Moon. From our perspective on the
Earth's surface we see two small bulges, one in the direction of the Moon and
one directly opposite. The effect is much stronger in the ocean water than in
the solid crust so the water bulges are higher. And because the Earth rotates much
faster than the Moon moves in its orbit, the bulges move around the Earth about
once a day giving two high tides per day.
Water on the moon ?
The Moon has no atmosphere. But evidence from
Clementine suggested that there may be water ice in some deep craters near the
Moon's south pole which are permanently shaded. This has now been reinforced by
data from Lunar Prospector. There is apparently ice at the north pole as well.
Composition
The Moon's crust averages 68 km thick and varies from
essentially 0 under Mare Crisium to 107 km north of the crater Korolev on the
lunar far side. Below the crust is a mantle and probably a small core (roughly
340 km radius and 2% of the Moon's mass). Unlike the Earth, however, the Moon's
interior is no longer active. Curiously, the Moon's center of mass is offset
from its geometric center by about 2 km in the direction
toward the Earth. Also, the crust is thinner on the near side.
There are two primary types of terrain on the Moon:
the heavily cratered and very old highlands and the relatively smooth and
younger maria. The maria (which comprise about 16% of the Moon's surface) are
huge impact craters that were later flooded by molten lava. Most of the surface is covered with regolith, a
mixture of fine dust and rocky debris produced by meteor impacts. For some
unknown reason, the maria are concentrated on the near side.
A total of 382 kg of rock samples were returned to the Earth by the Apollo and Luna programs. These provide most of our detailed knowledge of the Moon. They are particularly valuable in that they can be dated. Even today, more than 30 years after the last Moon landing, scientists still study these precious samples.
A total of 382 kg of rock samples were returned to the Earth by the Apollo and Luna programs. These provide most of our detailed knowledge of the Moon. They are particularly valuable in that they can be dated. Even today, more than 30 years after the last Moon landing, scientists still study these precious samples.
The surface of the Moon is covered by a soil layer
called regolith , which has been produced by meteorite impact.
With no atmosphere and no magnetic field, the Moon's surface is exposed directly to the solar wind. Over its 4 billion year lifetime many ions from the solar wind have become embedded in the Moon's regolith. Thus samples of regolith returned by the Apollo missions proved valuable in studies of the solar wind.
With no atmosphere and no magnetic field, the Moon's surface is exposed directly to the solar wind. Over its 4 billion year lifetime many ions from the solar wind have become embedded in the Moon's regolith. Thus samples of regolith returned by the Apollo missions proved valuable in studies of the solar wind.
A lunar eclipse
occurs when the Moon passes directly behind the Earth into its umbra (shadow).
This can occur only when the sun, Earth, and moon are aligned, or very closely so,
with the Earth in the middle (order: sun, earth, and moon).
Hence, a lunar
eclipse can occur only the night of a full moon. The type and length of an
eclipse depend upon the Moon's location relative to its orbital nodes.
A total lunar
eclipse has the direct sunlight completely blocked by the earth's shadow. The
only light seen is refracted through the earth's shadow. This light looks red
for the same reason that the sunset looks red, due to Rayleigh scattering of
the more blue light. Because of its reddish color, a total lunar eclipse is
sometimes called a blood moon.
Unlike a solar
eclipse, which can be viewed only from a certain relatively small area of the
world, a lunar eclipse may be viewed from anywhere on the night side of the
Earth. A lunar eclipse lasts for a few hours, whereas a total solar eclipse
lasts for only a few minutes at any given place, due to the smaller size of the
Moon's shadow. Also unlike solar eclipses, lunar eclipses are safe to view
without any eye protection or special precautions, as they are dimmer than the
full moon.
Types of Lunar eclipses
The shadow of the
Earth can be divided into two distinctive parts: the umbra and penumbra. Within the umbra, there is no direct solar
radiation. However, as a result of the Sun's large angular size, solar
illumination is only partially blocked in the outer portion of the Earth's
shadow, which is given the name penumbra.
A penumbral
eclipse occurs when the moon passes through the Earth's penumbra. The penumbra
causes a subtle darkening of the moon's surface. A special type of penumbral
eclipse is a total penumbral eclipse, during which the Moon lies exclusively
within the Earth's penumbra.
Total penumbral eclipses are rare, and when these occur, that portion of the moon which is closest to the umbra can appear somewhat darker than the rest of the moon.
Total penumbral eclipses are rare, and when these occur, that portion of the moon which is closest to the umbra can appear somewhat darker than the rest of the moon.
A partial lunar
eclipse occurs when only a portion of the moon enters the umbra. When the moon travels
completely into the Earth's umbra, one observes a total lunar eclipse.
SBB
source: http://nineplanets.org/luna.html
https://en.wikipedia.org/wiki/Lunar_eclipse
