Named for the messenger of the Roman gods, this fast-moving planet is closest to the Sun.
When most people get their first close-up look of the planet
Mercury, they usually mistake it for another celestial body…
Earth’s moon.
Mercury orbits the Sun at an average distance of about
57 million kilometers. With a diameter of only 4,908 kilometers,
it's not much bigger than our Moon. Since it usually gets
lost in the Sun's glare, it's really hard to see from Earth,
even with a telescope.
Mercury moves fast, orbiting the Sun once every 88 days. Like Earth's Moon, it is a crater-covered world and has little or no atmosphere. Unlike the Moon, there are long cliffs criss-crossing the surface of the planet. Scientists believe these formed as Mercury contracted while it cooled. Astronomers have found what they believe are ice caps in the polar regions of the planet.
When NASA scientists first analyzed the Mariner 10 data, they thought that Mercury was geologically inactive, with no signs of recent volcanic or tectonic activity. Some scientists have begun to re-think these findings. After looking at enhanced color images of the planet, they now believe there may have been volcanic activity on Mercury in the not-so-distant past.
Scientists hope to gather more information and answer some
questions about Mercury when a new probe, called Messenger,
begins orbiting the planet in 2007.
To see a close up image of Mercury, log onto the Mercury
Images link under External Resources.
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