LIFE IN OTHER WORLDS 



appearance is so bright, viewed from the earth, that it 

 has been surmised that what we see is not the planet itself 

 but its atmosphere always charged with clouds or possibly 

 snow. Of Mars as an abode of life, and of the Moon, 

 which is the body nearest to us, we shall speak more fully 

 in the present chapter. Coming to the outer major 

 planets, the giant Jupiter with a bulk more than a 

 thousand times as great as the earth has a constitution 

 by no means so solid. For many reasons the belief seems 

 j ustified that Jupiter must be a still hot, and almost gaseous 

 body, without a solid crust. If Jupiter's comparatively 

 small weight for its size and its wonderful and varying 

 system of cloud coverings are evidence of an early stage of 

 development and a high internal temperature, still more 

 is this the case with Saturn. In bulk it is not far inferior 

 to Jupiter ; but it is so much lighter than water that if 

 some of its fragments fell into one of the earth's oceans 

 they would float there. Its outer coverings or envelopes 

 must consist of heated gases in active circulation. Of 

 Uranus and Neptune, still farther off, we know very little, 

 and the progress of knowledge concerning them is very 

 slow ; but it is more probable that they are in the early 

 stage of development attributed to Jupiter and Saturn 

 than in the solid stage of planets like the earth. So that 

 we may fairly dismiss the probability of the existence 

 of life as we know it on any of them and neglect 

 incidentally, therefore, any possibility that life could have 

 been carried in a meteorite from them to us. Whether 

 there are other forms of " life " than any we know is a 

 question hardly needing discussion. 



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