The Moon
(TFS) - he 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
orbit: 384,400 km from Earth
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.
Eclipses:
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
https://en.wikipedia.org/wiki/Lunar_eclipse
