The Washington times., 1918-08-18
By Prof. Garrett P. Serviss.

" HE statement has several times re-
Gently been published that the spec
troscope reveals evidence of the ex-
istence of chlorophyll (the green coloring
matter of vegetable cells) on the planets
Uranus and Neptune, the two most distant
worlds of the solar system. In the imagin-
able consequences that it suggests this
statement is an astonishing one, since it
can be regarded as indicating the existence
of organic life under a new order of circum-
stances, totally different from those of our
world, some of the details of which, on
purely speculative basis, of course will be
pointed out as we go on.
The statement referred to is founded on
certain observations of lines, or bands, in
the spectrum of the light of the planets
Uranus and Neptune, the identity of which
with the characteristic marks of the sub
stance chlorophyl may be questioned.
This identification is Professionally ac-
cepted, however, by Dr. A D. c. Crommelin,
in recent book on astronomy. Let us
now consider what chlorophyll is and what
its presence on those distant worlds may
imply.
Chlorophyll as already stated, is the
green coloring matter of plants, and it is
found in all living vegetable cells. 1t is
not a simple element, like oxygen, nitro
gen, calcium, iron, etc, but is a complex
chemical compound. Its exact constitution
is still uncertain, but magnesium is said
10 be one of its indispensable constituents.
yhlorophyll is chemically related to the
proteids, which are 'by far the most COM
Dlicated of the compounds of living sub
stance" while they and their compounds
play by far the most important part of all
organic matter in the processes of life.
This is enough to show the immense
interest that attaches to the discovery OF
chlorophyll in the atmospheres of two
great planets, the smallest OF which,
Uranus, is sixty-five times as large as the
earth, while the other, Neptune, exceeds
the earth eighty-five times in size. On the
earth the only function, or we might say,
the only reason for the existence OF chloro-
phyll appears to be its agency in the main
tenance of living organisms. 1t lies at the
very basis of life in our world, for Vege'
tation is dependent upon it, while, in turn,
animal life cannot be maintained without
the food which chlorophyll enables veget-
able organisms to prepare from raw min
eral matter.
We cannot too strongly insist upon the
Significance of the fact that chlorophyll
is not known to exist for any other pur-
pose than to enable vegetable organisms
to derive their sustenance from the HE
less mineral world around them. The
further fact that il is very complex
compound, which seems to have Deen
formed only with reference to its peculiar
relation 10 organic life, renders its occur
renee upon other worlds so much the
more suggestive of the existence of the
living organisms in those worlds, and this
in spite of the vast difference between
the earths physical state and theirs.
Granting the existence of this mysteri-
Gus life-accOmpanying substance on
Uranus and Neptune. let us next consider
what the physical condition OF those
planets is and what circumstances pc
culiar to them would probably funda-
mentally affect the relation between
chlorophyll and vital phenomena there.
Take first the consequences OF their great
relative distances from the sun. Uranus
is at a mean distance Of LISP million
miles. while the distance Of Neptune is
nearly 2792 million miles, that OF the
earth being only 80 millions The most
striking consequence of such great re-
moteness from the sun is the resultant
loss of intensity Of the solar heat and
light, as compared with that intensity on
the earth.
On Uranus the sun gives only about
! 36Sth as much radiant energy per unit
of surface as it gives ON the earth, while
on Neptune the fraction is reduced TO only
lyg04th. The particular importance OF
this for our present subject becomes evil
dent when il is stated that chlorophyll is
active only in the presence Of light. Its
function for the plant is to absorb radiant
energy from the sunlight. and in some
manner not yet understood. 10 employ
that energy in forming carbohydrates
from the carbon dioXide gas contained in
the air From these carbohydrates the
plant is built up.
At first il looks as if this were a fatal
blow 10 the hypothesis that chlOrOphyll
may serve on Uranus and Neptune TO
build up organic life. But the objection is
more apparent than real, because the effec-
tive intensity Of the light on those planets
is, after all, far greater than the numerical
comparison indicates. Even on Neptune.
for instance, the solar light must be 700 or
500 times as bright as full moonlight on
the earth, while on Uranus the brightness
Of the sun is probably from 1000 to 1000
times that of the full moon. On the other
hand, terrestrial experience shows that a
moderate degree of sunlight is the most
favorable to the effective action of chloro-
phyll, so that it might turn out that, in
2