|Understanding Science and Nature: Space and Planets.Alexandria, Virginia, Time Life, 1992: 12.||"Mars' Mt. Olympus, 15 miles high and 300 miles wide, is the biggest volcano in the Solar System."||24 km|
|Lewis, Richard S. The Illustrated Encyclopedia of the Universe.New York: Crown, 1983: 130.||"The volcano [Olympus Mons] was calculated as 373 miles (600 km) across and 18 miles (29 km) above the base."||29 km|
|Whitehead, A. B. "The elevation of Olympus Mons from limb photography." Icarus. Vol. 22. (June 1974).||"The summit of Olympus Mons is found to be 22 plus or minus 1 km above the mean level of the surrounding plain by correlating the elevation results with previously reported planet radii at nearby occultation points."||21–23 km|
|Lang, Kenneth & Gingerich, Owen. A Source Book in Astronomy and Astrophysics. 1900-1975. Cambridge, MA: Harvard, 1979: 279.||"The volcanic structure is 500 km across and about 29 km high, with a complex summit caldera about 70 km across."||29 km|
|Arnett, Bill. Mars. Students for the Exploration and Development of Space (SEDS). 24 May 2001.||"Olympus Mons: the largest mountain in the Solar System rising 24 km (78,000 ft.) above the surrounding plain. Its base is more than 500 km in diameter and is rimmed by a cliff 6 km (20,000 ft) high …."||24 km|
Olympus Mons is not only the tallest mountain on Mars, but it is the tallest known volcano in our solar system. This extinct volcano was discovered by the Mariner 9, NASA's second attempt to put a camera spacecraft in orbit around Mars in 1971, along with three other huge volcanoes, all of which are now extinct. It was measured from Mariner 9 limb pictures that have the volcano in its foreground. Located on the Tharsis Plateau near the equator, Olympus Mons is bordered by an escarpment. The caldera in the center is 80 km (50 miles) wide and contains multiple circular, overlapping collapse craters created by different volcanic events. Olympus Mons' tremendous height is thought to be due to its volcanic activity and the flow of hot lava. Lava flow radiating 500 miles from the crater was clearly seen in the Mariner 9 photographs.
There is a discrepancy in the actual measurement of Mount Olympus. Because the measurements are actually estimations from the pictures of the Mariner 9, results for the height of the volcano range from 22 to 29 kilometers (14 to 16 miles) high. Also, some of the measurements were made from the base of the mountain, while others were done from the crater surrounding it, Nix Olympica. In terms of Earth's topography, Olympus Mons is taller than three Mount Everests, about as wide as the entire Hawaiian Island chain and it is larger than the entire state of Washington.
Marina Tsukerman -- 2001