LUNAR MYSTERIES

Evening Post, Volume CXIII, Issue 112, 14 May 1927, Page 17

LUNAR MYSTERIES

ORIGH OF THE CRATERS

UNSOLVED PROBLEMS

MASS ATTACK BY SCIENTISTS

Of all the heavenly bodies the moon, our nearest neighbour, is best known, and our knowledge of.this satellite of ours seems to bo substantially complete. Her size, distance, mass, and density are known so well that future investigators can only have the joy of adding one more'decimal placo (if they are lucky, and work hard) to a figure already pretty closely known.. Her motions in the heavens, although very complicated, have been worked out with great thoroughness and high precision, and little more apparently remains to

But, says "The Scientific American," we know little more of the surface details of the moon than our grandfathers did, if. they, too, were astronomers. '■ We can see finer details on the moon with -the - smallest telescope than we can hope to see on any other heavenly body with the greatest, and photography enables us to make accurate and complete records of all but tho^very smallest objects which we can see. .■'".' ' ' ;

Plains, mountains, craters, lines of cliffs, deep,- narrow cracks—all these have been seen, Samed, ana catalogued for half a century—yet we know little more of their nature and origin now than people did then. We know that there is neither air nor water on the moon; that its surface has the reflecting power (on the average) of rather dullish rock; that the rapid fall of brightness from the full moon to the half and the crescent.shows that the surface must be very rough, and covered with irregularities, some as big as mountains, some perhaps as small as pebbles, which, by their shadows, diminish the illumination except ' when we look right down the' path.of the sun's rays toward the full: moon—and all this was known 60' years ago. Since then we have found out a little; we know now that ,the ; moon's., gravitational attraction is insufficient to prevent its atmosphere from flying off, molecule by molecule; into space, and we are therefore sure that it never has had an atmosphere, or.water on its surface, sinco it became ah independent body. 1 ''■'■■■ ■'••■■

PROBLEM Or THE CRATERS. ' What formed the moon's,innumerable craters? Were they produced by'volcanic eruptions like/those which wo can observe on earth, or perhaps, as some have suggested, by the impact of gigantic meteors—:as appears to , have happened in Arizona so recently, that wind and rain, haye hot'had time to wear down even'the sides of the resulting crater? Why are the crater floors usually much below the level of the surrounding country? * And. why do some, and not. . others, have central luouirtains, rising high above the floor, but usually falling far short of the rim? Most puzzling x>f alt—why are a' few craters, such as Tyeho.and Copernicus, surrounded by whitish "rays'"— nearly straight streaks which extend far over the moon's surface sbmetynKs for hundreds of miles, running right over hill and dale—and why are these" "rays" much more conspicuous loai full moon than at other times'?

We know that the lunar craters were not all produced at once, for in a-number of instances one crater cuts into another, "biting .off" a piece "of its wall, in such, a way as to make it obvious at a glance that it was formed later than its neighbour, and, iii" its/formation, destroyed; a portion of its rim.'

jho huge size of some of the craters, } up to a hundred miles and mor.e in diaj meter, presents another,. puzzle. Most puzzling of all, in many ways, are the large dark areas which form the couspicuous spots visible without a telescope, and called by Galileo the maria (Latin for seas). They are not seas, 'however, but great plains—almost as level as the sea, of much darker rock than • the rest of tho surface, nnd with but. a few craters scattered hero and there' over their surfaces. ' '■•'.'. ■. . PROBLEMS TO BE SOLVED. Theso questions arc to-day unanswered; but they are probably not all unanswerable, provided that all available knowledge is brought to bear on their solution. For half a century the astronomers have usually taken tho moon's, surfaco details for granted without speculating much about it, and tho geolo'g.ists with a few exceptions have regarded them as outside their field of study. ' Many suggestions have been made to account for the surface phenomena of tho moon and many opposing theories advanced. Now, under tho auspices of tho Carnegie Institute, a combined attnck by astronomers, physicists, geophysicists, and geologists is to bo made in an endeavour to wrest theso secrets from tho moon, and it seems probable that- knowledgo of our dead satellite will bo much extended during tho next few years.