OUR NEIGHBOR WORLD

Hokitika Guardian, 24 July 1922, Page 1

OUR NEIGHBOR WORLD

WHAT WE KNOW ABIOUT THE PLANET MARS.

An astronomical correspondent writes to the “Manchester Guardian.” Mat's reaches opposition, on th e average, every two years and two months this period being due to the combined motions of the planet and our earth. But tho distance varies greatly’ at the different oppositions. Mars revolves round the s'tn in an orbit which is markedly elliptical in form, and ns the earth’s orbit also deviates considerably from a circle there is a point where the two pathways make their closest approach. It so happens that that part of our planet’s orbit which is traversed in the summer months lies nearest to tho orbit of Mars. When opposition takes place in August the distance is least—about 34,000,000 miles; in February it is greatest, about 60,000,000. Thusj ns seen by tho naked eye, the planet is much more brilliant during its summer apparitions than in winter and as seen in the telescope its disc is much larger. To us in the northern hemisphere, however, the winter and spring oppositions have a certain advantage. Mars is higher above tho horizon and visible for much longer periods, and is actually easier to observe, though its brilliance is less and its disc smaller.

resemblances to the earth

All oppositions of the planet, how ever are taken advantage of by astronomers, anj the results of their observations are followed by mnny who take but the mildest interest in things celestial. For. of all the planets oi our solar system, ns Sir William Herschel pointed out 140 years ago. Mars bears the strongest resemblance to our earth ; and so tho question presents itself whether or not onr planetary' neighbour is inhabited—whether indeed, we can discern traces on Mars of life and intelligence. Professor Pickering recently ontitled line of his articles “Mars: Things Known and Surmised,” nnd we may usefully consider the planet under these two heads. First of all, certain facts have been established as tho result of long years of patient study, and mayhe regarded as beyond all doubt. Mars is a considerably’ smaller planet than the earth. Its diameter measures 4200 miles, while its volume is 0.151 that of our world »nd its mass 0.108. The “day” of Mars—the period of rotation oil its axis—is only about half an hour longer than our own day, 24 hours 07 minutes 22.6-5 seconds, and the axis is inclined to the plane of the orbit by nearly the same amount as in the ease of the earth. Tlio Martian seasons are, therefore, practically tho same as ours. There is tho same succession of spring, summer, autumn, and winter. The year, however, is almost twice as long; for Mars revolves round the sun in an orbit exterior to the earth and at a- slower rate. Its period o( revolution is 087 terrestrial days. The atmosphere is considerably thinner than ours, which is to he expected for the smaller mass. It is according to the lato Professor Lowell, “thinner at least by half than the air on the summit of the Himalayas,”. Mot only is the air thinner it is much clearer. Cloudy days are the exception, not, ns with us, tho rule. Indeed, the nights are cloudier than the days, generally speaking, though, of course, there are cloudy seasons, especially at the beginning of winter, before the snow begins to fall. THE FAMOUS “CANALS”. Of tho existence of snow and ice on Mnrs there can he no doubt. Tho polar caps have been observed for over two centuries, and the salient fact

about them is their seasonal fluctuation. They increase in size in late autumn and winter, and melt in the lato spring and summer seasons, and as they melt, they are seen to ho encircled by open polar seas—temporary bodies of water generated by the rapid melting of the snow fields. These are tho only seas which exist on Mars. The blue-green areas formerly believed to

ho oceans have long since been demonstrated to lie simply tracts of vegetation ; for they change color with the

icasons, becoming verdant in the sum

mer after the melting of the caps. Tho greater portion of the surface of Mars

however, is reddish-ochre in tint, and this is desert land, analgous to the deserts of our own world. For Mars is scarce of water, and the proportion

of desert is much greater than with us. These deserts, however, are intersected by numerous long straight lines, first recognised by the great Italian astronomer Schiaparelli in 1877. These are the famous “canals” concerning

the nature of which controversy lias raged since their discovery. They aio of all degrees of visibility, and exist in the darker regions a s well a s in the desert lands. Most of them- converge to various centres, and at the junctions of two or more are to ho observed the round spots known as “oases” first seen h.v Pickering in 1892. The most remarkable fact about tho system of ennals nnd oases is that its degree of visibility depends on tho seasons. As tile cap melts in the late spring and early summer, the canals darken and the oases become prominent—a fact which proves conclusively that tho phenomenon is .vegetal in character, that the canals and oases are fertilo regions irrigated by the water from tho melting caps.

Here we pass from tli o region of things known to that of things surmised. What is the meaning and function of the canal system ? We do not certainly know, and have to bo content with hypotheses more or less probable. It used to bo bold by tho majority of astronomers that the canals were largely optical illusions, but this view may now ho regarded as disproved by the seasonal nature of tho phenomenon. There remains Professor Lowoil’s well-known hypothesis that the canal system is the handiwork of a race of intelligent beings who arc hard pressed by the scarcity of water on the