Rensselaer Democrat, Volume 1, Number 6, Rensselaer, Jasper County, 20 May 1898 — THE ATMOSPHERES OP PLANETS [ARTICLE]

THE ATMOSPHERES OP PLANETS

A Theory that There la No Water On Mirra. A very curious method has very recently been used by Dr. G. Johnstone Stoney, the English physicist, to find the composition of the atmosphere of the planets. Some time ago Dr. Stoney accounted for the absence of an atmosphere on the moon by" reminding us that according to the accepted theory of gases every gaseous molecule moves In a straight line with great velocity till it is turned aside by an encounter with another molecule. Since the moon Is a small body whose attraction is slight, the gases around it would in course of time dart off Into space, particle by particle, only those being left that are close to the surface, where the attraction is strong enough to hold them. This would be true also for any other heavenly body, but the larger the body the greater the distance at which its gravitation would hold the gSs, and the thicker its atmosphere would be. As the molecules of lighter gases move with higher velocities, these would fly off when heavier gases remained. This would account for the rarity of free hydrogen In the earth’s atmosphere. The discovery of tlie gas helium, together with the certainty that It Is not found free in our atmosphere, has enabled Dr. Stoney to make his data more exact, since helium is twice as heavy as hydrogen. Says Nature, in a review of Dr. Stoney’s paper, which appears In the Transactions of the Royal Dublin Society: “It is contended that helium is continually being supplied to the earth’s atmosphere from hot springs, that it exhibits no tendency to combine with other elements, and since no trace of it can be found in the atmosphere It escapes above, as rapidly as it enters below. Water vapor, on the other hand, remains on the earth, anil consequently limits of si>eed can be assigned between which gases are either imprisoned or are free to escaped From calculations based on these facts the following conclusions are reached regarding the atmosphere of the different planets, using the known intensity of gravitational attraction on the surface of each:

“Limiting the inquiry to a temperature of 6 degrees C.. Dr. Stoney applies the theory to all members of the solar system, with the following results: From the moon all gases having a vapor density less than 39 will pass with greater promptness than helium does from the earth. On Mercury water canuot exist, while nitrogen and oxygen would gradually dribble away. The conditions on Venus resemble those on earth, but the case of Mars Is of exceptional interest. Dr. Btoney says that it Is legitimate to Infer that on this planet water cannot remain. The atmosphere he considers to consist mainly of nitrogen, argon anil carbon dioxid. He thinks there Is no vegetation, as we understand the term, on the surface of the planed, and’ the snow, frost and fog do not arise from the same cause as on the earth. Jupiter is able to imprison all gases known to chemists, but w’hethcr vho more distant members of our system can retain hydrogen Is doubtful. Helium and the denser gases probably float in their atmospheres, but the molecules of the lighter gases are describing orbits about the sun, the velocity they can acquire enabling * them to escape from planetary control, but still insufficient to liberate them from the gravitational Influence of the sun.”—Literary Digest.