Are the Planets Inhabited?

d that the Earth exceeds in volume 5000 times, we are confronted by one that exceeds the Earth 1400 times. Ceres, when viewed through a l

late Prof. James Keeler, an observer of the first rank, having the advantage of observing the planet from the summit of M

n places extended into the red belts as long streamers.... Near their junction with the equatorial zone, the streamers were white and definite in outline, but they became redder in tint toward their outer extremities, and more diffuse, until they were lost in the general red colour of the background. When the seeing was good they were seen to be formed of irregular rounded or feathery clouds, fading toward the outer ends, until the structure could no longer be distinguished.... The portions of the equatorial zone surrounding the roots of well-marked streamers were somewhat brighter than at other places, and it is a curious circumstance that they were almost invariably suffused with a p

nd not only is the speed of rotation of the whole very rapid-Jupiter turns about its axis in a little less than ten hours, so that a particle at its equator moves through 466 miles in each minute-but the various items that form the bands rotate in differ

t and heat, its mean temperature would sink to -30°C.; the Earth's being 16°C. Mars is therefore almost always a frozen planet; frozen except on its mere surface when this is exposed to the full rays of the Sun. No sea there would ever be melted to a depth of more than a few inches, even at n

cannot be so. The density of the Sun is 1·4 that of water, Jupiter's is 1·33, showing that but a very small proportion (if

e nearer to its centre. The great mass of Jupiter points to its inherent store of heat being much greater than that of any other planet. And of two bodies equally hot, the larger must cool more slowly than the smaller. If, therefore, all the members of the solar system had at one and the same moment possessed the same surface temperature, that equality would have ceased directly they began to radiate their heat into space; the temperature of the smaller bodies falling mo

radiation is kept up is supplied by its volume. It follows, therefore, that a large and

mines the state and condition of the surface; it is the underlying power. Two men may be contending in a financial struggle; to the eye they may look alike, equally prosperous; both may have the same amount of money ac

that mass, yet in general, and neglecting other considerations, we can say that of two worlds the one with the greater mass will be that with the higher inherent temperature. This factor of inherent temperature was one that did not require to be noticed in dealing with the Moon, or V

t emits more light than it receives. This is now generally regarded as an excessive estimate, but the albedo of the disc as a whole cannot be put lower than 0·72, or about that of white paper. But many of the "belts" or da

ows in transit appear very dark, it is clear that they are not absolutely black, since sometimes such a shadow is not distinguishabl

btain, and the atmosphere of Jupiter would be much denser and much shallower than that of the Earth. Denser it probably is; shallower it cannot be, for the great white spots, each often five or six thousand miles in diameter, that range themselves at times along the equa

. The clouds and storms of our own atmosphere are worked by solar heat; solar heat it is that draws up the vapours and provides the chief part of the energy manifested in the speed and strength of the ai

he Earth, such inequalities connected with a given difference in latitude are spread over eleven times the distance that they would be on the Earth, and are, therefore, so much the less pronounced. Yet, across a gulf of 400 millions of mi

giving a rotation period of 9h. 50m. while the equatorial belt in general gives a period 5m. longer; so that in 119 rotations

had a history practically as long as our telescopic knowledge of the planet, and may be looked upon as in some sort a permanent feature. Yet that it is not in the nature of a portion of a solid crust is clear. It occupies on Jupiter much the position and relative area of Australia on the Earth, but whereas Australia of necessity rotates in one piece with all the o

l without a solid crust; probably without a solid nucleus, liquid or vaporous throughout. Whatever the future may hold for such an orb, it is clearly no world for habitation at present. Full of colo

life to its satellites? For Jupiter is sun-like, not merely in its own condition, but also in that it

f his possession of a telescope-need be considered; the other four are of the

ermost, is almost exactly the size of Mercury; Io, the innermost, is midway between the two in its dimensions. But Ganym

om the Sun. It is true that Jupiter presents to Ganymede a disc with more than 200 times the apparent area that the Sun presents to the Earth, but to make up for the falling-off of the solar radiation, each unit of this area should radiate about 1?250th as much heat as each unit of the

-Suns; sources of a certain amount of heat, and not recipients merely. The days are yet far distant when a solid crust can form on any one of them, and the water condense from the steamy a