The planet Venus is an uninhabited planet, 109 million kilometers from the sun, making it the second closest planet (“Facts about the planet Venus”). Being also the sixth largest planet in our Solar System, it measures 12,100 km in diameter, similar to that of the Earth (“Planet Venus Facts”). Because of their similarities in size, Earth and Venus are often called “twins” (Feather and Zike 77). Venus was first discovered by ancient astronomers due to its visibility with the naked eye, but they were unable to identify what it was (Cain). Since this occurred before recorded history, it is impossible to pinpoint exactly who saw it first in the sky (Cain). In 1610, Galileo confirmed that Venus was indeed a planet, as it too had phases, just like our moon (Cain). Even though Earth and Venus are similar in size, the similarities stop there. . Because Venus is much closer to the Sun, its revolution lasts only about 225 Earth days (“How Long Does It Take Venus to Go Around the Sun?”), moving at 35 kilometers per second (“Facts about the planet Venus”). However, its rotation lasts 243 Earth days, making one day longer than a year ("Facts about the planet Venus")! Besides Uranus, Venus is the only planet to rotate from east to west (“Facts about the planet Venus”). Venus' atmosphere is extremely dense (Feather and Zike 77). Many of the clouds surrounding the small planet are composed primarily of sulfuric acid (“Facts about the planet Venus”). The air itself is 96% carbon dioxide and no oxygen has been detected, and the surface pressure is 92 times that of the Earth's atmosphere (Coffey, “Atmosphere of Venus”). For all this, Venus is strongly influenced by the greenhouse effect which causes a small temperature variation from 450°C to 475°C all...... middle of paper....... 2008. 14 Nov. 2013 ..Coffey, Jerry. "Temperature of Venus." Universe today. May 15th. 2008. November 18, 2013..Feather, Ralph M, and Dinah Zike. Astronomy. New York: Glencoe/McGraw-Hill, 2013."How long does it take for Venus to go around the Sun?" IPAC. August 27, 2013. November 13, 2013.the-Sun->.Macintosh, Zoe . “NASA May Target Venus for Future Missions.” NBC News. July 30, 2010. November 18, 2013. "Missions to Venus." Windows on the Universe. 2012. November 18, 2013.."Facts about the planet Venus." Facts about the planet. 2013. November 13, 2013. < http://planetfacts.org/planet-venus-facts/>.