Evening star., 1942-07-21
Of Stors, Men
And Atoms
Notebook Of Science Progress
In Laboratory, Field
And Study
BIZ Thomas r. Henri.

The worlds most delicate thermome-
ter, designed to measure temperatures
of selected areas on the planet Mars over
more than 100000 miles of empty
space, has been designed at the United
States Bureau of Standards.
1t now becomes at least theoretically
possible to determine by these heat
measurements the kinds of rocks which
make up the surface of the only place
in the solar system outside the earth,
where there is much possibility OF life.
The new instrument just described by
w. W. Coblentz of the bureau staff is
an extremely sensitive thermocouple-a
junction between two wires of different
elements. When an electric current is
sent over this junction the resistance
varies precisely with the amount Of heat
radiation which falls on it. With tele-
scope the radiation from limited part
Of the Martian surface can be focused
on the junction. The current change,
after allowances have been made for
the absorption in the earths atmosphere.
denotes the temperature of the spot
from which the radiation is focused.
All the light from Mars Is reflected
sunlight. The dying planet radiates
nothing Of it's own. When the suns
rays fall on its surface some are absorbed
in the rocks and others reflected imme-
diately. Different kinds of rocks reflect
different wavelengths. With the new
instrument it Is hoped that it will be
tn 1iofi
quite narrow bands Of the solar spectrum.
The amount of radiation which is re-
f1ected primarily by silica, felspar or
mica will give rough figure for the
amounts Of these rock substances on the
Martian surface. In this way it may
be possible to construct geological map
OF the planet.
measurements Of the Marian tempera-
lures were made during close approach
Of the planet to the earth in 1926. At
that time he used junction Of platinum
and bismuth wires. Extensive expert
ments have shown that better values can
be obtained with junction of platinum
and new metal composition, chromel P,
which is about 80 per cent magnesium
and 10 per cent chromium. It is also
hoped that it will be possible to focus on
such junction the radiation from
smaller area of the planet which, at the
best, seems only large star to the naked
eye. With a powerful telescope, however,
it appears about as large as the full moon.
The most precise measurements DR..
Coblentz has yet made of planetary
temperatures show that at the equator
OF Mars at noon In midsummer the
thermometer may rise to between so
and so degrees Fahrenheit. In the
North Tropical Zone. equivalent to such
region as Mexico on the earth, the
maximum is between 30 and 40 degrees,
and as the North Pole is approached the
temperature falls to between go and
TO- The measurements showed that
there is very rapid drop to below freez-
ing everywhere at sunset and q slow rise
after sunset. f4
Thermocouple measurements are not
entirely inconsistent with the presence
of some low form of animal life in the
equatorial regions. DR. Coblentz points
out, however, that much depends on the
figures adopted for the absorption Of
radiation in the earth's 100-mile- thick
blanket Of atmosphere, for which allow
ance must be made in the calculations.
Some recently determined figures, the
accuracy Of which is not universally
accepted, indicate that the temperatures
actually are much lower-probably be-
low the minimum which would permit
any sort of life such as is known on
earth. If 1t can be assumed, however,
that the major constituents Of the Mar
tian rocks are felspar mica and silica, as
is the case on earth, there is fair agree
ment with the previous calculations.