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This image shows what it would look like to be orbiting a few hundred kilometers above Mercury's surface with your back toward the Sun. Among the stars, you can see the Earth and the Moon as the blue speck and its tiny companion. The view was created using imagery from NASA's Mariner 10 spacecraft but with computer manipulation to provide color and the orbital viewpoint. The inset (right) is a composite photograph of the full disk of Mercury by Mariner 10; the blank strip at the upper right was not photographed. (Image above from the Voyage scale model solar system, developed by Challenger Center for Space Science Education, the Smithsonian Institution, and NASA. Image created by ARC Science Simulations © 2001.) |
The innermost planet, Mercury, lies just a few steps from the model Sun. Mercury is the smallest planet except for Pluto, and in our model it is only about as big as the period at the end of this sentence. Mercury is a desolate, cratered world with no active volcanoes, no earthquakes, no wind, no rain, and no life. Because there is virtually no air to scatter sun-light or color the sky, you could see stars even in the daytime if you stood on Mercury with your back toward the Sun. You wouldn't want to stay long, however, because the ground on Mercury's day side is nearly as hot as hot coals (about 425°C). Nighttime would not be much more comfortable: With no atmosphere to retain heat during the long nights (which last about 3 months), temperatures plummet below -150°C (about -240°F)--far colder than Antarctica in winter.
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This map shows Mercury's location in the Voyage scale model solar system on the National Mall in Washington, DC. The dot at the top of the page (next to title) shows Mercury's size on the scale. |