jholt%Nosc@usiiden.UUCP (05/01/85)
From: <crash!usiiden!jholt@Nosc>
[forwarded from the InterComEx BBS (303) 367-1935 by joe holt]
WHAT'S NEW ON THE MOON?
-----------------------
(excerpts from a publication by Dr. Bevan M. French, NASA
Exterestrial Materials Program)
In 1969 over half a billion people witnessed the "impossible"
coming true as the first men walked on the Moon. For the next
three years people of different nationalities watched as one of
the great explorations of human history was displayed.
Between 1969 and 72, supported by thousands of scientists on
Earth, 12 astronauts explored the surface of the Moon. Protected
against the airlessness and the killing heat of the lunar
environment, they stayed on the Moon for days and some of them
travelled for miles across its surface in Lunar Rovers. They made
scientific observations and set up instruments to probe the
interior of the Moon. They collected hundreds of pounds of lunar
rock and soil, thus beginning the first attempt to decipher the
origin and geological history of another world from actual
samples of its crust.
The initial excitement of new success and discovery has
passed. The TV sets no longer show astronauts moving across the
sunlit lunar landscape. But on Earth, scientists are only now
beginning to understand the immense treasure of new knowledge
returned by the Apollo astronauts.
The Apollo Program has left us with a large and priceless
legacy of lunar materials and data. We now have Moon rocks
collected from eight different places on the Moon. The six Apollo
landings returned a collection weighing 382 kilograms (843 lbs)
and consisting of more than 2000 samples. Two automated Soviet
spacecraft named Luna 16 and Luna 20 returned small but important
samples totalling about 130 grams (5 oz).
Instruments placed on the moon as long ago as 1969 are still
detecting moonquakes and meteorite impacts, measuring the Moon's
motions and recording the heat flowing out from the inside of the
Moon. The Apollo Program also carried out a major effort of
photgraphing and analyzing the surface of the Moon. Cameras on
the Apollo spacecraft obtained so many accurate photographs that
we now have better maps of the Moon than we do of some areas of
the Earth. Special detectors near the cameras measured the weak
X-rays and radio activity given off by the lunar surface. From
these measurements, we have been able to determine the chemical
composition of about one quarter of the moon's surface, an area
the size of the U.S. and Mexico combined. By comparing the flight
data with analyses of returned Moon rocks, we can draw
conclusions about the chemical composition and nature of the
entire Moon.
Thus, in less than a decade, science and the Apollo Program
have changed our Moon from an unknown and unreachable object into
a familiar world.
Is there life on the Moon?
--------------------------
Despite careful searching, neither living organisms nor fossil
life have been found in any lunar samples. The lunar rocks were
so barren of life that the quarantine period for returned
astronauts was dropped after the third Apollo landing.
The Moon has no water of any kind, either free or chemically
combined in the rocks. Water is a substance that is necessary for
life and it is therefore unlikely that life could ever have
originated on the Moon. Furthermore, lunar rocks contain only
tiny amounts of the carbon and carbon compounds out of which life
is built and most of this carbon is not native to the Moon but is
brought to the lunar surface in meteorites and as atoms blasted
out of the Sun.
What is the Moon made of?
-------------------------
Before the first Moon rocks were collected, we could analyze
only two types of bodies in our solar system, our own planet
Earth and the meteorites that occasionally fall to Earth from
outer space. Now we have learned that the Moon is chemically
different from both of these, but it is most like the earth.
The Moon is made of rock. The rock is so much like Earth
rocks in its appearance that we can use the same terms to
describe both. The rocks are igneous, which means that they are
formed by the cooling of molten lava. (No sedimentary rocks like
limestone or shale, which are deposited in water have ever been
found on the Moon.)
The dark regions (called "maria") that form the features of
the "Man in the Moon" are low, level areas covered with layers of
basalt lava, a rock similar to the lavas that erupt from
terrestrial volcanoes in Hawaii, Iceland, and elsewhere. The
light colored parts of the Moon (called "highlands") are higher,
more rugged regions that are older than the maria. These areas
are made up of several different kinds of rocks that cooled
slowly deep within the Moon. Again using terrestrial terms, we
call these rocks gabbro, norite and anorthosite.
Despite these similarities, Moon rocks and Earth rocks are
basically different and it is easy to tell them apart by
analyzing their chemistry or examining them under a microscope.
The most obvious difference is Moon rocks have no water at all
while most Earth rocks contain at least a percent or two of
water. The Moon rocks are therefore very well preserved since
they never were able to react with water to form clay minerals or
rust. A 3 1/2 billion year old Moon rock looks fresher than water
bearing lava just erupted from a terrestrial volcano.
Another important difference is that the Moon rocks formed
where there was almost no free oxygen. As a result, some of the
iron in lunar rocks was not oxidized when the lunar lavas formed
and still occurs as small crystals of metallic iron.
Because Moon rocks have never been exposed to water or oxygen,
any contact with the Earth's atmosphere could "rust" them badly.
For this reason, the returned Apollo samples are carefully stored
in an atmosphere of dry nitrogen, and no more of the lunar
material than necessary is exposed to the laboratory atmosphere
while the samples are being analyzed.
The Moon rocks are made of the same chemical elements that
make up Earth rocks, although the proportions are different. Moon
rocks contain more of the common elements calcium, aluminum and
titanium than do most earth rocks. Rarer elements like hafnium
and zirconium, which have high melting points are also more
plentiful in lunar rock. However, other elements like sodium and
potassium, which have low melting points are scarce in lunar
material. Because Moon rocks are richer in high temperature
elements and contain less low temperature elements, scientists
believe that the materials that formed the Moon was once heated
to much higher temperatures than material that formed the Earth.
The chemical composition of the Moon also is different in
different places. Soon after the Moon formed, various elements
sorted themselves out to form different kinds of rock. The light
colored highlands are rich in calcium and aluminum, while the
dark colored maria contain less of those elements and more
titanium, iron, and magnesium.
What is the inside of the Moon like?
------------------------------------
Sensitive instruments placed on the lunar surface by the
Apollo astronauts are still recording the tiny vibrations caused
by meteorite impacts on the surface of the Moon and by small
"moonquakes" deep within it. These vibrations provide the data
from which scientists determine what the inside of the Moon is
like.
About 3000 moonquakes are detected each year. All of them are
very weak by terrestrial standards. The average moonquake
releases about as much energy as a firecracker, and the whole
Moon releases less than one ten billionth of the earthquake
energy of the Earth. The moonquakes occur about 600 to 800
kilometers (370 to 500 mi) deep inside the Moon, much deeper than
almost all the quakes on our own planet. Certain kinds of
moonquakes occur at about the same time every month, suggesting
that they are triggered by repeated tidal strains as the moon
moves in its orbit about the Earth.
A picture of the inside of the Moon has slowly been put
together from the records of thousands of moonquakes, meteorite
impacts, and the deliberate impacts of discarded Apollo rocket
stages onto the Moon. The Moon is not uniform inside, but is
divided into a series of layers just as the Earth is, although
the layers of the Earth and Moon are different. The outermost
part of the Moon is a crust about 60 Km (37 mi) thick, probably
composed of calcium and aluminum rich rocks like those found in
the highlands. Beneath this crust is a thick layer of denser rock
(the mantle) which extends down to more than 800 Km (500 mi).
The deep interior of the Moon is still unknown. The Moon may
contain a small iron core at its center, and there is some
evidence that the Moon may be hot and even partly molten inside.
The Moon does not now have a magnetic field like the Earth's
and so the most baffling and unexpected result of the Apollo
program was the discovery of preserved magnetism in many of the
old lunar rocks. One explanation is that the Moon had an ancient
magnetic field that somehow disappeared after the old lunar rocks
had formed.
One reason we have been able to learn so much about the Moon's
interior is that the instruments placed on the Moon by the Apollo
astronauts have operated much longer than expected. Some of the
instruments originally designed for a one year lifetime, have
been operating since 1969-70. This long operation has provided
information that we could not have obtained from shorter records.
The long lifetime of the heat flow experiments set up by the
Apollo 15 and 17 missions has made it possible to determine more
accurately the amount of heat coming out of the Moon. This heat
flow is a basic indicator of the termperature and composition of
the inside of the Moon. The new value, about two thirds of the
value calculated from earlier data, is equal to about one third
the amount of heat now coming out of the inside of the Earth. As
a result, we can now produce better models of what the inside of
the Moon is like.
As they probed the lunar interior, the Apollo instruments have
provided information about the space environment near the Moon.
For example, the sensitive devices used to detect moonquakes have
also recorded the vibrations caused by the impacts of small
meteorites onto the lunar surface. We now have long term records
of how often meteorites strike the Moon, and we have learned that
these impacts do not always occur at random. Some small
meteorites semm to travel in groups. Several such swarms,
composed of meteorities weighing a few pounds each struck the
Moon in 1975. The detection of such events is giving scientists
new ideas about the distribution of meteorites and cosmic dust in
the solar system.
The long lifetime of the Apollo instruments has also made
several cooperative projects possible. For example, our
instruments were still making magnetic measurements at several
Apollo landing sites when, elsewhere on the moon, the Russians
landed similar instruments attached to their two automated lunar
roving vehicles (Lunokhods). By making simultaneous measurements
and exchanging data, American and Russian scientists have not
only provided a small example of international cooperation in
space, but they have jointly obtained a better picture of the
magnetic properties of the Moon and the space around it.
What is the Moon's surface like?
--------------------------------
Long before the Apollo Program scientists could see that the
Moon's surface was complex. Earth based telescopes could
distinguish the level of maria and the rugged highlands. We could
recognize countless circular craters, rugged mountain ranges, and
deep winding canyons or rilles.
Because of the Apollo explorations, we have now learned that
all these lunar landscapes are covered by a layer of fine broken
up powder and rubble about 1 to 20 meters (3 to 60 ft) deep. This
layer is usually called the "lunar soil," although it contains no
water or organic material and it is totally different from soils
formed on Earth by the action of wind, water, and life.
The lunar soil is something entirely new to scientists for it
could only have been formed on the surface of an airless body
like the Moon. The soil has been built up over billions of years
by the continuous bombardment of the unprotected Moon by large
and small meteorites, most which would have burned up if they had
entered the Earth's atmosphere.
These meteorites form craters when they hit the Moon. Tiny
particles of cosmic dust produce microscopic craters perhaps
1/1000 of a millimeter (1/25000 inch) across, while the rare
impact of a large body may blast out a crater many km or miles in
diameter. Each of these imnpacts shatters the solid rock,
scatters material around the crater and stirs and mixes the soil.
As a result, the lunar soil is a well mixed sample of a large
area of the Moon and single samples of lunar soil have yielded
rock fragments whose source was hundreds of km from the
collection site.
However, the lunar soil is more than ground up and reworked
lunar rock. It is the boundary layer between the Moon and outer
space, and it absorbs the matter and energy that strikes the Moon
from the Sun and the rest of the universe. Tiny bits of cosmic
dust and high energy atomic particles that would be stopped high
in the Earth's protective atmosphere rain continually onto the
surface of the Moon.
[this was just one posting on this BBS. if you liked this, i'll
forward s'more (most are of this length or shorter - some, tho',
are tremendously long, like NASA's *complete* file on Venus).
here's a list of others: various shuttle missions, the NOAA
satellites, AXAF array telescope, space lab 2 & 3, IRAS IR
satellite, possible solar systems, young astronauts, Venus
Pioneer to view Halley's comet, AGDISP program, orbital transfer
vehicle, orbital maneuvering vehicle, Galileo mission to Jupiter,
review of 1984, the moon [what ya got above], Halley's comet
(long), Mars-Viking mission (review), Venus technical data...
crash!usiiden!jholt@nosc]otto@nic_vax.UUCP (05/02/85)
> From: <crash!usiiden!jholt@Nosc> > > [forwarded from the InterComEx BBS (303) 367-1935 by joe holt] > > > WHAT'S NEW ON THE MOON? > ----------------------- > > > > [this was just one posting on this BBS. if you liked this, i'll > forward s'more > > crash!usiiden!jholt@nosc] send us more ... more ... more !!!!! - Doug Otto
henry@utzoo.UUCP (Henry Spencer) (05/03/85)
Unfortunately, this article is a little out of date. The instruments
left on the Moon by the Apollo missions were turned off some years ago,
to save the pittance it cost to receive and record the data. ARGH.
--
Henry Spencer @ U of Toronto Zoology
{allegra,ihnp4,linus,decvax}!utzoo!henry