WHAT THEY SAW

Press, Volume LX, Issue 18234, 19 November 1924, Page 10

WHAT THEY SAW

WHEN MARS WAS . NEAREST. LICK ASTRONOMER'S STORY QUESTION OF LIFE THERE STILL A MYSTERY. The exceptionally close approach of Mais, to our earth on August. 23rd of this year excited-more popular interest than any other astronomical phenomenon since the appearance of Halley's co.ihet in 1909-10, writes-.Robert G.. Aitkeh in the "New-York-'Times." And this.is not surprising, for, aside from its brilliance and'its flaming red colour at a favourable opposition, which would attract the notice of the most casual observer, the planet Mars is the one most closely associated in our thoughts with the age-old question of the possibility that life may exist on worlds other than our own earth. Even when Mars is in the more distant parts of its orbit, and-so faint that only the astronomer is likely; to recognise, it ih'the sky, .there is no question that is so often put by visitors to an observatory as the one, "Do you think Mars is inhabited?" It was to be expected, therefore, that interest in the subject would increase when • the planet became so prominent; but the insistence of the demand for information about what we are doing /to increase our knowledge of our neighbour in the sky. surprised, I think, nearly every astronomer. At the Lick Observatory, telephone queries, telegrams, and letters poured in upon us; reporters came, up. to get stories, and .visitors, on' our. public nights showed .but '.one see 'Mars. New Knowledge. Now, the/ astronomer shares the f' v eneral interest in our planet neighbours ;' he is at least as curious to know about conditions there as the layman is, and ha is quite as much interested in the;question of life on other wo'rlds as* any other man. But he has naturally a better idea of the difficulties that beset the attempts to find out "more about ihese matters,- and is, therefore', less sanguine of an immediate solution to the problems, I think it not too conservative to say that no astronomer expected.to make any sensational discovery by reason of the re- . cent vety .close, approach of the planet. ;No one:, of ::us; for. exarhple,- anticipated Te.cemng or any. other ' kind—from, the Martians.- We did not even hope to get a definite answer to the question as to whether of not there are any Martians. What we.did expect, and I think weshallnot be disappointed, is that by the application .of"Some, new methods.of investigation ..which jiave recently. become, available we' mav make some advance in our knowledge of the .Martian atmosphere. .of the. nrobable temperature on the. surface of vthe, planet,, and possibly, as to .the reason-for, the -observed colour .changes in /certainilarge, areas as -the seasons change, on:Harsi-.," ".:. ;.. Before d'iseussitig.these methods, andthpir possible- results let: us' . consider the- conditions.:-.under, which we must acquire our knowledge of Mars, or any other .heavenly body, and then summarise briefly the definite knowledge that has resulted from the patient labour of scpres of trained observers. Mars -at its nearest is 1 very, 'nearly ;-85< millions of miles, jrom the earth, -and ■ ourrac'euf ate ■measures 'of "its 'diameter show- that this is; only 4200.miles.' ; At best,- then, the planet appears no larger than a one-foot disc will if viewed from a little over ene ' and a half miles. 'With; the eye^alohe.such a disc would be. entirely. invisible, unless it • were mad© extfelnely , -.brilliant, -then.: it . would as "Mars does to the;unaide^.:eye.',,Viewed '-with modern : powerful: telescopes,-..and. the highest inagnifying. powers, adapted to the study, of planetary surfaces,. Mars is about as large as the moon is to'the •naked.eye... The images on. the photographic plate are very much smaller, for they are usually made directly in the focus of the object glass; or mirror, or, if "an enlarging lens is interposed, it ordinarily does not magnify mo.re than about-threefold. Hence the original photographs are of the order of onequarter or one-third of an. inch in diameter, or even smaller.' Of course these may, be. enlarged photographically microscope In-'- either-case, however, the grain of the plate is also enlarged, and there is a sharp limit to the useful scale.. of enlargement. Speaking generally, nothing is gained by - enlarging the image to a diameter much greater than an inch.

Mars Was Ideally Placed. This is why the astronomer does inot become greatly excited, about a difference of a few hundred thousand or even a few million miles in the distance of an object which at'nearest is 35,000,000 miles away. A matter of far greater importance, to : him. is:that the planet shall be:so-placed that its rays • in reaching his-.telescope take the shortest possible 'path through- our own most troublesome atmosphere. Throughout the present opposition Mars has been ideally, placed for. observers in the Southern Hemisphere, for it is about seventeen degrees south of the celestial Equator, and therefore passes through the zenith for-observers in latitude of seventeen degrees south of our Equator. Unfortunately, there are few telescopes of hny great siae in the Southern Hemi-. sphere. To reach us in our northern latitudes the light from Mars must pass very obliquely through our . air strata and suffer greatly from their turbulence. It is hardly too much to say that for-use the opposition of Novembers 1926; when Mars is 8;0O0,0OU miles further away, will be quite as favourable as the present one' because then the planet 'will be more than thirty degrees higher in our sky. Nov/ just what do we positively know about our nearest neighbour on our right so to speak—the one just beyond us in order of distance from the sun? We know its diameter, asi I have already stated, and hence its surface and its volume. From our measures of its two tiny moons—discovered ; by Asaph Hall at the Naval Observatory Hi.lß77—we can derive avalue of its mass arid hence of its density. Its volumes;is.l/7, Jts mass 10/94, and its density is .0.73, the values for the earth being taken as unity in each case. There are numerous larger markings on the planet than are visible in the same relative position at every, opposition. Hence we know that they must be surface markings;, not phenomena of the Martian atmosphere. These markings slowly move across the face of the planet, proving that the planet rotates on its axis, and careful comparison of their positions at oppositions separated _by many years, has given us a - Tery accurate-knowledge of its rotation -22.87".-secoridß. "Hjßnc©*heMartian : day and" night-are- almosti-precisely equal to our own" "Moreover, observations-of the polar caps and" other markings have shown "that" the' axis of rotation is inclined 24 decrees 50- minutes to the orbitr plane. Since the axis of the earth rotation is' inclined" 23J degrees to its orbit t plane, the .Martian seaspns are like our own in their succession', and practicallv- like our-'own in. their character ' except for one particular—it takes Mars 22$ of our months, instead of twelve- likV-the earth, -to travel once about the sun. Hence the Mar-

tjan year and each Marxian season are 'nearly twice as long as our own. Polar Caps and Dark Mar&tngs. This very nearly completes the items that are entirely, beyond dispute. The great majority of .astronomers, however, from' the appearance of the polar caps and the dark markings, the occasional obscuration of some details and the occasional appearance of small projections at the terminator, are convinced that Mars has some water and some atmosphere, enough to produce snowfalls at the poles and occasional clouds elsewhere, though fajr too little of either to make the planet a comfortable abode for creatures like ourselves. The precise amount is a matter open to question, and even more' questionable are the forms and outlines of the finer details of the planet's surface-'.marking's and the interpretation to be given. to'-them. Wei-have all. heard -much of- the "canals" of Mars. ; The fact is-that observers differ. extraordinarily in their delineations of these markings. Some draw them as very narrow, uniform, straight-lines (arcs of great cireles) that make a geometrical net on the-face of the planet. Other observers of equal skill and experience—the late Professor Barnard for one—have never been able to.see such fine lines with.any telescope., Bear in mind what has been.said-about the:size of the -and photographic images of liars; and: this: trjli not be entirely .surpfjsing, "\{~ '.,^PJ Photography nas been appealed to; ; for photograph's of Jupiter -and of Saturn show detail' of •' the' same character- aV that of careful drawings, and'no ofle questions the appearance of either planet. Opinion is not unanimous as to how.far the photographs of Mars support the contentions of the - differing visual observers.;. My 'o;wn Opinion is .that as far, as_ they g<? they supjort those .whoi while noting a>wealth.of fine detail on the planet's- surface, fail to see anything like a geometrical network" of narrow "canals," or' indeed anything that can fairly be. said, to have an artificial appearancei' ..' .'. ,: ■ "Photographs taken at the Lick Observatory, arid doubtless -at others, -'during .the present opposition, differ M.one yery important - from'..'ihpse Ttaken 1 namely, in: that we;now' have plates, that. are sensitive; tb long;-.wave ; length : red light; as. well-.as ordinary photographic plates sensitive 'to shprt wave-length violet light, arid; those sensitive to the- rays of intermediate wave length, which, because they most' strongly affect the eye, we call visual • rays. A comparison of these plates mises to add significantly to pur-know-ledge of the naturo and extent of'the atmosphere of Mars. At Flagstaff and at Mount Wilson measurements of theheat radiated from the pianet in general ' and' from different regions ; of its surface.haye been niade by instruments almost incredibly sensitive. These-must give us a better understanding of the temperature on the Martian surface.

Both of these lines of research will obviously have a direct bearing upon the question of the habitability of Mars, but definite results are not available as I write these lines. I may, however, say that - comparison of thedifferent series of photographs taken by Astronomer H. Wright with the Crossley reflector of the Lick, Observatory shows that the Martian atmosphere is of ■ sufficient extent and density definitely to affect the brightness of the planet at- what we call the *-' limb," that is, around the outer circumference. It also appears "that this atmosphere is practically opaque to short wave length violet light, but is readily penetrable by red light of long, wave.' length. These are perhaps the most significant photographic results so far obtained for Mars; but it is desirable to wait until the investigation .is complete before .attempting their precise interpretation.

The Question of Life There. Summing it all up, we may say that the balance of evidence is in support of, the conclusion that conditions on Mars are moderately favourable to the "existence of life, which, like life here on'.the earth,, is dependent upon water, air,..and a moderate temperature, ; and that is the .only kind of life about which argument is possible.,' If the changes in colour on certain ■ parts of the surface denote vegetation developing in the spring.and turning sere and brown in the autumn, then.undoubtedly

we may conclude /that tar item' 4 ~ '* animal life are also-prases! a ' far, with full knowledge* of %lfeii that have been made to tl«'«a£js£ I have no hesitation shave not a shred of d'ence that intelligent fife «sa&w the planet. I am per3Mfe4 8b&& vast majority of astronoa»aa,'i^^^ : to this conclusion. . "%n!T Astronomers are in speang&:fej* that the only, other plane! at;8»a», : tern that is at all to bV<mrffcssi ' connexion with the ' existence of life is YeaßS. ' planets, Jupiter, 1 Neptune,-are probably out. That is, no one of planet with -aMercury, on the other,ly regarded as a solid .tically, rio .atmosphere *3|EJS7 AJ Venus,, in respect of •«» t *l£p ! || $ earth's twin; it is newer testfiraas and therefore receives mars fepptf 1 it, but not an exeessrre j appearance suggests .dense, cloud-filled that very atmosphere jpnmtejfHflfr 1 ' ing the planets surface. tiona there may Jfavoar Ufi£|ra|p| ,but whether or not "habited we do not kae^^Jj^iMfJ 3Ve. have,, then, oto pos&atf 1 - that intelligent life planet in "the solar system earth. Have we as* reams. wN£> that it exists eleeimre |sT Mln verse?' From' direct The very nearest star HissrJ[gf||||i ; 'times -as far away from 88 is. Viewed from that atoMjjvfy would be quite, one of the planets^in'ear *ris£l|Mlli with any telescope va.xMf y§|l||| ' sess, or- with" any that i^**s^^^^R' all possible to construct. we cannot hope to gefe ofejjfjfjjlli' evidence that planets* attawi^^g i the suns in space whfcs! ifa ifffijit' But consider tiaese. .scope like our 3&-indt on Mount Hamilton will *Hf&Mf 80 million sfcws. like our.great refleritoqtj,*lgliy of photographing ber. "We have good sw^mMR 1 that fully, .1000 milßoa saan'iwgg, our system. la* *?s2§j§§S we have l>eeh increasing *?jJBBK of the sine and ; stars, or suns, and of and motions in space t '*SSS wildering repidity. We sun is iust an ordinary guishable from many ■™? I *2E2 others, if viewed front #» aSKS* tanee; it is larger than but certainly smaller tbaa **sgfT centage, if not the majotite > .L«lfgttL. it is not at the centre system, bnt, so far froa ~»ffil~|jK from stars at: or near il»«j^ l |MW|t 11s.only .-rfter trawlliag tWfflfflß for several thousand yvmtfyW&fi of 186,000 miles a flW *?^Xi"ji' Is it reasonable to ordinary star, .oar spa*- *s*jjj!KfS an- inconspicuous poatfee IMJTaBlfj. importance in tite should be the oady one tary system, and of the smaller-bodies. ews system, should be 1 the universe that is fcteal»fflf,%wjHP gent life? I» not gious anthropocentric M«» iH&jK can well conceive? utterly absurd. To my vaxm^W&i' ; rational conclusion is tfofc ww^g 1 many thousands of the planets attending them •"JgIES these there must be maiqF w*»fP7Q. abode of intelligent lifes - * ™ *?f ■ - 1 1 ————* * A) >