Page 44 - Curriculum Visions Dynamic Book

The Moon’s atmosphere
Look at any picture of the Moon showing the view into space, and you will see
that the lunar sky is always black. That
is because the blue sky we are used to
is created by light waves being altered (called diffraction) as they enter our atmosphere. Without a substantial atmosphere that cannot occur, and so the Moon’s sky is invisible.
The low gravity of the Moon means
that any gases present on the surface tend
to float away more readily than they do
on the Earth. That is why there is no thick atmosphere encircling the Moon. That
does not mean there is no atmosphere at all; but it is extremely thin, and molecUles in it are so sparse that they rarely collide.
When we make a sound on the Earth, it is carried through the air by molecules colliding with each other. Without collisions of molecules there can be no sound through the air. The Moon is therefore silent. If you were able to speak without a space suit, no sound would come from your mouth.
The main gases naturally present are neon, hydrogen, helium, and argon. Argon is released from lunar rocks by the decay of radioactive potassium. Neon, hydrogen, and helium come from the solar wind
that blows all around the Moon.
The atmosphere is neither thick enough
to have any braking effect on anything moving about, nor can it develop winds.
Without the atmosphere and winds that we have, and with no oceans to soak up heat and regulate temperatures, the surface of the Moon reaches over 120°C during the day but drops to –170°C at night.
 The surface of the Moon is covered with many large rocks and also a thin layer of soil almost like dust. You can get a clear idea of the surface from these pictures and the one on pages 48–49.
(Top left) Astronaut Buzz Aldrin steps down to the lunar surface during the Apollo 11 mission. Notice that the lander does not sink into deep soil.
The detail (bottom left) shows a bootprint and the thin layer of dust that covers the Moon’s surface.
(Opposite top right) There is no wind on the surface of the
Moon because there is so little atmosphere. That
is shown by the fact that the flag has to
be supported along its top edge.
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