STUDIES OF THE SKIES

Taranaki Daily News, 19 July 1935, Page 3

STUDIES OF THE SKIES

SOME BAFFLING, . • ___ ; ATMOSPHERES OF PLANETS. CONSIDERABLE ADVANCE MADE.. ' i . ~~~~~~~~ Considerable advances have been made recently by means of the spectroscope attached to the largest telescopes in the study of the atmospheric conditions prevailing on the chief planets of the solar system, writes the astronomical correspondent of tije Manchester Guardian. The spectrum. of Jupiter, which has been most closely studied, is, of course, largely a replica of that of the sun, as Jupiter shines by reflected sunlight. There are; however, certain lines and bands peculiar to the planet’s spectrum which obviously proceed from Jupiter itself. The existence of many lines unmistakably due to ammonia has now been confirmed at Mount Wilson by Dr. Dunham,•' who has also found lines due to methane, or marsh gas. These lines are characteristic of the spectra of the four outer planets, but, according to Dr. Spencer Jones, “the bands due to ammonia are strongest in the spectrum of Jupiter and become less conspicuous in the spectra of Saturn, Uranus and Neptune. The bands due to methane, on the other hand, become stronger from Jupiter to Neptune.” . COLD PDANETS. These gases are compounds of hydrogen with nitrogen and carbon. Ammonia' is produced in minute quantities by .atmospheric electricity, and methane occurs naturally under certain conditions. As its popular name, “marsh gas,” signifies, it is formed by the decomposition of vegetable matter, more particularly in marshy places. The existence of such gases in large quantities in the atmospheres of tne giant planets would appear to afford decisive evidence that they are not hot and sunlike worlds, as the famous and longaccepted “Zollner-Proctor” theory postulated, but .very cold; for under high temperatures ammonia and methane are both dissociated. Low temperatures for the giants are indicated also by recent radiometric measure at Mount Wilson. Theoretically, the present'd of these, to us, strange gases is not difficult to explain. Large and massive planets must contain an excessive amount of hydrogen, part of which must long ago have combined with the available oxygen to form water, which, at the low temperatures of the outer planets, can only exist as a layer of ice at the surface. The remainder of the hydrogen, at a higher level, must have combined with nitrogen and carbon to form ammonia and methane. The clouds of Jupiter and Saturn are believed to consist of crystals of ammonia. ‘ t ■ EXCLUSIVE OXYGEN. Recent studies of the atmospheres of Venus and Mars have yielded. surprising and in some cases discordant results. The atmosphere of Venus is very dense and cloud-laden. Indeed, it is to its canopy of cloud that Venus owes its excessive brightness; for it reflects about 60 per cent of the. sunlight which it receives. The spectrum of Venus - has been carefully studied within the last ten years, at both the Lowell and Mount Wilson Observatories. Dr. Adams and Dr. Dunham, using the 100-inch Mount Wilson telescope, found no lines corresponding to oxygen, or water vapour, and so they conclude that “if oxygen or water vapour exist in appreciable quantities in the atmosphere of Venus it must be at a level below that to which ,the spectroscopic observations penetrate.” They identified two bands peculiar to the spectrum of Venus with carbon dioxide. This is all that is known for certain.

The atmosphere of Mars, though cbrisiderably rarer than ours, is quite appreciable, the observations of Dr. Wright, of the Lick Observatory, indicate that it is considerably denser and more extensive than was formerly supposed. In 1908 Dr. Slipher at the Lowell Observatory found evidence of the lines of water vapour in the spectrum pf Mars and this was confirmed by Dr. Adams and Dr. St. John at Mount Wilson in 1925. They detected, or thought they de- . tected, the presence of water vapour to the extent of 5 per cent of that nor- , mally present in our own atmosphere, and free oxygen to the amount of 15 per cent. !' ' ‘ More recently, however, Adams and Dunham, using the great spectrograph of the 100-inch telescope, again photographed the spectrum of Mars with a view to confirming their previous result To their surprise, they found no evidence whatever of the presence of oxygen, and concluded that" “the amount of free oxygen present in the atmosphere of the planet must be extremely small, certainly less than 1 per cent, and probably less than 0.1 per cent, of that present in the earth’s atmosphere over equal areas of the surface.” Evidently this conclusion has a definite bearing on the question, of the habitability of Mars, for animal life as we know it cannot exist without oxygen. But the existence of vegetation, presumably akin to our terrestrial vegetation, seems to be established beyond all doubt by telescopic observations, and all forms of vegetable life emit oxygen. Further, the existence of oxygen in combination with hydrogen is definitely proved by the existence of temporary seas and the polar snows. .The recent observations at Mount Wilson cannot, therefore, be accepted as conclusive. The general atmospheric circulation on Mars has been investigated by Dr. Coblentz and Mr. Lampland in recent years. Owing to the absence of permanent oceans on Mars, “climatic conditions are no doubt simpler than ours,”»they believe. “While it is summer in one hemisphere, and the sun’s' rays are melting the polar snows, what little vapour exists is travelling, probably by diffusion and by strong winds, to the opposite hemisphere, to be deposited as snow at that Pole where the temperature is'the lowest.” In the case of Mercury, the nearest planet to the sun, the Mount , Wilson observers detected no difference between its spectrum and that of the sun. This would indicate that there is no appreciable atmosphere, which is to be expected on theoretical grounds, on account of the small mass of the planet. On the other hand, the telescopic observations, of M. Antoniadi, by means of the great refractor at Meudon, in France, suggest that there is a thin, though deep, atmosphere full of dust clouds, formed as a result of the partial disintegration of the rocky surface under the blazing heat which the planet endures—seven times more intense than the solar heat received by our own world.