Evening star., 1937-06-29
STARS, MEN AND ATOMS
Notebook of Science Progress in Field,
Laboratory and Study.
BY THOMAS r. HENRY.

Chunks Of disrupted planets, hitting
the airless surface of the moon at We
locities from 20 to 40 miles a second
are responsible for the pock marked sur
face of the earths satellite, according to
data presented before the American As
sociation for the Advancement of Science
by DR.. L. J. Spencer, British geologist.
Parts of the moon are so pitted that
they really look as if they were made
of green cheese"
An alternative theory in the past, Dr.
Spencer explained. has been that the
marks are scars left by eruptions of
extinct volcanoes. They are not, how
ever, deep depressions on high elevations
such as are the craters of existing VOL
canoes on earth. Nor are they holes in
the surface, but rather great level areas
surrounded by high walls from which the
surrounding surface slopes away.
This is exactly what would result, DR..
Spencer said, from such a collision. A
body 100 feet in radius moving at such
speeds would hit the unprotected sur
face of the moon with mass of a million
tons, penetrate for q mile or more, COM
pressing the rock beneath it until there
resulted great explosion, and be blown
into thousands of fragments which would
scatter for miles around.
Meanwhile, the compressed rock would
be showed up by the force of the explo-
sion, forming the floor" of the crater
and the walls around it. There would
also be great "moonquakes," shaking and
cracking the surface.
A popularity of these moon craters
consists of shining lines radiating from
one of them for hundreds of miles in all
directions. These, he said, probably are
made up of tiny spheres Of shining metal,
most probably the iron of the original
meteorite.
The earth would be subjected to
similar fate, DR.. Spencer said, were 1t
not for the thick protecting blanket of
air which reduces to nothingness the 20
600 900 meteorites day which strike the
edge of the atmosphere. Thus, he pointed
out, only four craters similar to those on
the moon are known on EARTH one OF
which Is the great meteorite crater in
Arizona. Within historic times only one
meteor of sufficient size to make such q
crater has struck the surface of the
globe This fell in Siberia in 1908 Shocks
were felt around the earth, but the spot
where 1t hit never has been located.
The region is almost as inaccessible as
the moon itself.
Moreover, he pointed out. the celestial
bombardment of the moon seems to have
stopped. No new craters have appeared
in recorded history. This may mean,
he said, that the great chunks of iron
or rock which were left over when the
solar system was formed have almost
all been used up and only smaller bits
of interplanetary debris are still whirling
around in space.
The craters visible on the moons sur
face, he believes are relatively recent. In
addition to these markings are the vast
black areas which once were thought to
be oceans. It is known that the moon
is waterless and the "seas" now are sup
posed to be relatively level deserts of
basalt thrown up by erupting volcanoes.
Sometimes craterS appear in the middle
of seas, thus indicating later age.
X X X X
Two remarkable fragments of shooting
stars have just been added to the meteor
collection of the Smithsonian Institu-
ton.
One. about the size of 4 small walnut,
was picked up by an Indian last Winter
on the ice of a small lake near Great
Bear Lake in Northern Canada. In
trlgued by such funny stone, he took
1t to . nearby mission.
Smithsonian geologists easily denti-
ned It ~ visitor to earth from outer
space. IN Hself 1t represents . rather