Venus - Astronomically Speaking

by Joelle Steele

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Venus, the second planet from our Sun, is named for the ancient Roman goddess of love and beauty, and most of its features are named after women — real or mythical. It is the third brightest object in the sky after the Sun and Moon. It is 67.2 million miles (108.2 million km) from the Sun and ranges from 25-100 million miles (15-60 million km) from Earth. It has been referred to as both the Morning Star and the Evening Star because it is always within 48 degrees of the Sun, and when it is east of the Sun it appears before sunset, and when it is to the west of the Sun, it appears before sunrise.

Venus rotates east to west and has the slowest rotation of any of our planets. It take 243 earth days for it to complete one turn, yet its entire year takes only 225 earth days. In other words, its year is shorter than its day. Like our own Moon, Venus goes through phases (crescent, quarter, and gibbous) as it orbits the sun and the angle of the Sun-Venus-Earth changes.

We have taken a closer look at Venus courtesy of such exploratory spacecraft as the Mariner 10 in 1974 and Magellan in 1991. Other data about Venus comes to us from the Pioneer Venus orbiter and from the Soviet Veneras 13 and 14. The photographs and radar images transmitted from these spacecraft have given us a lot of valuable information about Venus.

It may be beautiful to admire in the sky, but Venus has a decidedly hostile environment. Its thick atmosphere, roughly 90 times denser than that of Earth, is composed of carbon dioxide, and creates 92 times the surface pressure of Earth. This makes for a greenhouse effect which causes surface temperatures to soar up to 900 degrees F (500 deg C). The thick clouds composed primarily of sulfur compounds — sulfuric acid in particular — obscure the surface and move in a global weather pattern.

Venus does not have any satellites (moons). It is a terrestrial planet like earth, with mountain ranges, ridges, deep chasms, and three large impact craters ranging from 23 to 39 miles in diameter. Its surface is believed to be composed primarily of grey basalt and it is covered with dust and small stones on top of volcanic rock. There are two large volcanoes called Maat Mons (named for the Egyptian goddess of truth) and Sapas Mons (named for an ancient Phoenecian goddess). Sapas Mons is about 1 mile high and about 120 miles across and is similar to the kinds of volcanoes found on Hawaii, complete with radial lava flows. Maat Mons is much steeper and is about 5 miles high with lava flows of 100 miles or so in length.

This article last updated: 11/09/2005.