Friday, July 27, 2007

The Planets

Here's my long-awaited posting on the first three planets in our Solar System. Interesting that we call them "the first three" since evidence suggests they were the latest planets formed. Anyway, there's an outstanding book on the subject called Astronomy: A Visual Guide, by Mark Garlick, for those who are fascinated by this sort of thing.

Mercury:
Diameter: 3031 miles (38.2% Earth)
Mass: 0.055 Earth
Mean Surface Temperature: 800 F (430 C)
The closest planet to the Sun, Mercury is a scorched, airless ball of iron covered with a thick crust of rock. Astronomers suspect the planet was originally much larger before a collision with a proto-planet, billions of years ago, blasted pieces of it into space. Mercury resembles the moon: an endless sea of craters. This is because the planet lacks an atmosphere and has never had water on its surface: the only erosion comes from the occasional impact of meteorites.

Venus:
Diameter: 7521 miles (94.8% of Earth)
Mass: 0.95 Earth
Mean Surface Temperature: 900 F (490 C)
Venus has been called Earth's sister because of its similar mass and size, but our nearest planetary neighbor is anything but Earthlike! The surface is permanently hidden beneath an atmosphere of carbon dioxide choked with clouds of sulfuric acid. This noxious sky pushes down on the surface with a pressure equivalent to that at the bottom of a lake nearly 900 M deep. The atmosphere is a heat trap, too. Despite being farther from the sun than Mercury, Venus is hotter. Both tin and lead would melt there.


And last, but certainly not least, my favorite planet:


Earth:

Diameter: 7926 miles
Mean Surface Temperature:
72 F (22 C)
Mass: 13,140,000,000,000,000,000,000,000 pounds
The largest of the terrestrial worlds, Earth is the only planet in the Solar System capable of maintaining liquid surface water. In fact, 70% of the planet's surface is covered in it, many miles deep in places. It's also the only planet known to support life: is this very common? Or quite rare?

There are posts on the other planets here.

Hope everyone is enjoying their summer!

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