HABITABILITY OF MARS

Shannon News, 27 November 1928, Page 4

HABITABILITY OF MARS

SOME INTERESTING OBSERVA-

TIONS.

Some of the most remarkable observations .of the ; planets which have ever, been made were described to. the JRoyal Astronomical Society by Dr. W. H. Wright, of the Lick Observatory, California, in delivering the annual George Darwin lecture (says the Morning Post). The method which has been used to photograph the planets in light of different colours by the suitable use of colour filters, i and to compare the results. By such means it has been demonstrated among other things, that Mars -has" an atmosphere whose height may bo , given tentatively as about 120 \miles ,in which meteorological changes take place similar to those of the eafjh. The method is capable, of' further development, of giving much more important evidence on the jnuch-discusscd question of the habitability of Mars than any yet obtained.

Photographs or the planet in ultra-, violet and in red light differ greatly in appearance, chiefly in the fact that the latter show much more detail than the former. The explanation is readily, obtained by photographing distant landscapes on the earth in the respective colours. It is then seen that a similar effect is obtained, because our atmosphere is mSch more transparent to red than to violet and ultra violet; in other words, we can penetrate much more deeply by red than by ,ultra violet light. In the case of the planets the difference between the two photographs can therefore be attributed to the existence of planetary atmosphere. That •the effect is more than can be accounted for by our own atmosphere is shown by repeating the observations on the moon, which has no atmosphere of its own. It is then found that the difference between the photographs is very much smaller than/that which characterises the planetary photographs. The conclusion is that the red light shows the surface of the planet, whereas the ultra-violet light shows its atmosphere since ultra-violet light from the surface would be absorbed before reaching the earth.

Mars has two “polar caps" which have been held to be formed of snow, and for the distribution of which over the planet the so-called canals have been said, by advocates of tho habitation theory, to have been constructed. The new photographs show conclusively that these caps are at least partly atmospheric. They appear to be precipitated in the atmosphere from much larger clouds, of which tho Martian atmosphere 5 contains many, and which in general undergo irregular changes similar to those of terrestrial clouds. Dr. Wright is not. convinced, however, that they are formed of water drops, like our clouds, and is, in fact, rather inclined to the contrary opinion. The atmosphere of Mars is not so clear as ours; measurements indicate that it is at least twice as obscure. The surface features of the planet have undergone marked changes in a period of two years, but it is not possible at present to determine the cause of this. # Similar, observations of other planets have been - made with very interesting results. Possible indications of a hitherto unknown fourth ring of the planet Saturn have been obtained, but further observations, which cannot be made until seven-years hence, are necessary to settle the question. With consummate skill and industry Dr. Wright has prepared a kinematograph film showing the planet Jupiter in rotation —of course, at a greatly accelerated speed. This was exhibited to the audience, and evoked loud applause. The new method of investigation is the most important advance in the study of the planets which has been made for many years, and has already thrown an entirely new light on many longstanding problems.