Evening star., 1902-02-22
SNOW ON THE MOON ?
CRITICISM OF THE THEORY AID.
VANCED By PROF. PICKERING.
Brilliantly White Spots on the Lunar
Surface That Grow Smaller After
Exposure to Sunlight.
From the London Standard.

From the London Standard.
The theory that there is snow on the
moon has been supported by the high au-
thority of Porf Pickering of Harvard Col
lege observatory. 1t is an opinion, we may
remark, which will require no little prov
ing. AS, however, the professor has done
little more than mention the principal
ground for his views, criticism Is, perhaps,
premature; but we may fairly inquire
whether no other interpretation is possible.
The professor has .heen carefully watching
certain brilliant white areas on the surface
of the moon, and finds that they grow ap-
preciably smaller after continued exposure
to sunlight, which, of course, would hap
pen with beds Of snow. But in that case
the moon would have some kind of an at
mosphere which must be capable of alb
sorbing the vapor of water. All the OBJ
servations of astronomers, however, have
led them to conclude that it possesses
nothing worthy of the name. The intense
light which illuminates it's surface, the
black shadows thrown by it's peaks, the
hard sharp outlines Of every feature on it's
disk, are Incompatible with a vaporous
veil to diffuse the glare and mitigate the
darkness. Besides this, the moon some
times comes between the earth and a star,
for a time hiding the latter from our view,
and this can be observed at the very mo-
ment Of disappearance. But If the moon
had at atmosphere in any way compare BILE
with that of the earth, the star would dis
appear, not suddenly, but gradually.
No Vestige Of Clouds.
Certainly no vestige Of a cloud has ever
been seen to traverse the moons surface,
and it would be passing strange II these
had been wholly preciptated during the
lunar night, and no morning mists had re-
mained to be just flushed with the rose of
dawn. 1t is open, perhaps, for believers in
the snow to assert that the moon once
had an atmosphere, and that though the
bulk of 1t has long since disappeared into
space some faint traces of a gaseous COW
ering may still linger near it's surface. But
this would hardly suffice to produce, dur
ing the lunar night. snow enough to linger
through it's not less long day. AS it's at
mospheric envelope cannot be comparable
with that of the earth the heat by day and
the cold by night would be more intense
than in the most arid region of our planet;
SO that no small mass of snow would be
needed to outlast the suns unshaded and
lOng-continued glare. There is, however,
another explanation to be ventured. The
moon, it must be remembered, is one mass
Of extinct volcanoes-a huge and Hfeless
globe of Stag Some of their craters are on
a much grander scale than any on our
earth. The opposite walls Of one are as
far apart London is from Cambridge,
floor is equal to that of Mont Blanc. When
these were in violent eruption an atmos-
phere did, Of course, exist; for vapor of
some kind would be necessary for such ter
rible explosions. But as the attraction of
gravity is so much less on the moons sur
face than 1t is here this atmosphere would
more readily disappear, as 1t had practical
ly done before the astronomers began to
take their notes.
A Mass Of Lava.
But the moons surface, as we have said,
Is mass of lava, and as-the average dens-
ity of the whole satellite is only a little
more than three-fifths of that of the earth
it is probably formed Of the same mate
rials. But the terrestrial lava streams are
often CLASSY in the outer part; indeed some,
like obsidian, retain this condition to a
considerable depth. On the moon there Is
no rain to rust or rot. no vegetation to
soften and darken the surface; the intense
heat Is the cause OF expansion, the cold of
contraction, and each must be sudden, thus
producing incessant fracture In the ex-
posed rock, that the moons surface
may well be like gigantic heap of CLASSY
Stag when broken up for road metal. The
innumerable faces Of these fragments
would glitter IN the sunlight. and this, not
improbably, would be better reflected to us
when 1t struck obliquely on the disk of the
satellite.