MERCURY
Mercury has the extreme maximum and minimum temperature. It is the nearest one to the sun, about 50 to 70 million km away. During the day, the temperature here shoots up to 430 degree C, but takes a plunge at nights to – 180 degree C. It spins incredibly fast that it completes one orbit around the sun in just 88 days! So, in just 58.6 days it completes one rotation. Thus, a day in Mercury is stretched for 59 times than the earth’s day!
Except for planet earth, the duration of the day and night depend on how fast it rotates. This was discovered by Johannes Kepler (1571 -1630), the German astronomer.
An amazing thing about Mercury is that, on two occasions it comes closer to the sun in its routine lap of orbit. It is called as Perihelion. Another interesting feature is that, a large bowl-shaped cavity named Colons Basin is about 1300 km diameter and 2 km deep! Besides, there are numerous such cavities dotted all over Mercury, which the scientists reckon, had formed due to its core that cooled down resulting in its shrinkage.
The formation of it, especially the mantle and crust, are of rocks. However, nearly three quarter of its diameter is iron. It appears to be almost amber in colour due to the presence of wide spread yellow dust and cavities seen all over the surface. This way it resembles the planet earth’s moon! According to the scientists, these were formed during the existence of the solar system about four million years ago. The dusty surface of Mercury was due to debris crashing on to it.
The space craft Mariner 10 that probed Mercury in 1974 named some of the cavities there after the celebrities like, Shakespeare, Beethoven, (Leo) Tolstoy, Bach and Wagner!
Mercury is, of course, a smallest planet. It is just about 5 per cent of the earth’s size and 20 per cent of the mass of earth. It has small polar ice-caps. With its extreme temperatures, Mercury never harboured any life.