Stardate 11:16:97
Mercury is a world of extremes.
This quick little messenger has a mass of only about 1/20 the mass of the Earth, and a diameter just 40% that of our home planet. Being the closest planet to the Sun, The side of Mercury facing the Sun can reach temperatures of 330 degrees c (625 degrees F); hotter than the hottest home oven. At night, however, the temperatures on Mercury can drop to below -170 c (-275 F); much colder than the coldest temperature ever recorded anywhere on Earth.
Mercury is the closest planet to the Sun, revolving around our planet star at a distance between 45,900,000 km (about 30 million miles) and 69,700,000 km (around 43,500,000 miles). In relation to the Earth, Mercury has an orbital distance of between 30% and 40% the distance from the Earth to the Sun. Because Mercury is about 1/3 the distance from the Sun as the Earth is, that means Mercury receives about 9 times the radiation from the Sun as the Earth does. The extremes in temperature are caused by the fact that the mighty solar wind at that distance has driven off any atmosphere that may have, at one time, existed on this now airless world.
One exiting new idea about Mercury comes to us through lunar observation. The lunar probe Clementine has reported finding ice in the eternally shaded craters at the lunar poles. That opens up the possibility that ice (probably water ice) may one day be found in the craters at the poles of Mercury.
Only
one space probe has ever approached Mercury. Perhaps we will one
day send a probe to explore frozen lakes on this barren world.
The gravitation on Mercury is only about 40% that of the Earth.
That means a 200 lb person would weigh only 80 lbs on Mercury.
Talk about a weight loss plan! Now the only trick is to live long
enough in those temperatures and breathe. The lack of any atmospheric
pressure would also make anyone unfortunate enough to suddenly
find themselves on Mercury explode. Not a minor inconvenience
by any stretch of the imagination.
All planets follow an orbit determined by a principle of physics known as Kepler's third law, or harmonic law. This simply states that the square of the period of an orbit is equal to the cube of it's distance from the Sun. What this means is if a planet were 3 times further from the Sun than the Earth is, it would have an orbit of the square root of 3 cubed, or 9 years. All planets follow this relationship ALMOST perfectly.
Mercury, however, shows the largest deviation from this law. Why the planets don't follow this relationship exactly was a question from the time of Kepler until the time of Einstein. The theory of relativity predicted a slight deviation in the orbits of the planets from that which was predicted by Kepler. When Einstein's equations were applied to the planet Mercury, the orbit predicted by Einstein turned out to match the observed orbit of Mercury perfectly. This was one of the first of many proofs of the great man's theories.
Mercury is a world of impact basins, much like our own Moon. The largest of these is known as the Caloris Basin, and is located in one of the hottest areas on the planet. The crater is 1300 km (over 800 miles) across, and formed mountains 3 km (nearly 2 miles) high. The impact which formed this basin spread debris for 800 km (500 miles) across the surface of the planet.
Look for Mercury low in the south west just after sunset, in the dimming twilight. While you're there, get yourself some ice. You're going to need it.
Clear skies, and good viewing.
