Kenneth Gilmour, age 10, of Peterborough, Odor is question:
How hot is the planet Mercury?
Mercury is the planet closest to the sun. We might say that this little planet has his toes right up close to the Big Furnace. But if this is so, he certainly does not have his back to the fire. You might think that the little planet is near enough to the sun to become warm clear through. But this is not so at all. To be sure, the side facing the sun is very, very hot indeed hot enough to melt lead. But the other side is very, very cold.
This baby of the Solar System orbits the sun once in 88 earth days. It also turns around on its axis once every 88 days. Its day and night period is equal to its year. This means that the same side of the little planet is always facing the sun and the other side is always facing away from the sun. One side, then, is always scorching hot and the other side is always bitterly cold.
The orbit of Mercury is about 36 million miles from the sun. The orbit of the earth is almost 93 million miles from the sun, and you know how hot we can get on a summer’s day. At the center of the sunny side, the temperature of Mercury is estimated to be 400 centigrade degrees. The twilight zones between the sunny side and the dark side are, no doubt, more comfortable. On the dark, cold side of eternal night, the temperature may be minus 200 degrees centigrade.
Until about ten years ago, it was thought that Mercury had no atmosphere. Now we suspect that a thin, filmy haze clings to the sunlit side. A dense atmosphere would carry the surface heat clear around to the dark side of the planet.
Mercury's atmosphere, what there is of it, is too thin to do this and so the dark side must be almost as cold as absolute zero which is minus 273.16 degrees centigrade.
No life as we know it could exist on this world of extremes. Some day, Mercury may be visited by our astronauts, for it would be a fine spot from which to view the heavens. Its twilight zones might also be used to launch space ships. Its mass is much less than that of the earth, which means that less fuel would be needed to launch ships and rockets.
The diameter of little Mercury, a line straight through the middle from side to side, is 3,100 miles. The diameter of our golden moon is 2,160 miles. Mercury is somewhat larger than our moon but is not as large as some of the big moons of Jupiter and Saturn. It is without doubt the baby of the planets, being quite a bit smaller than Pluto who pedals around the far outside orbit of the Solar System.