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Discover of Mercury by Early Astronomers, Missions - Windows to the Universe

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The Spring 2011 issue of The Earth Scientist is focused on modernizing seismology education. Thanks to IRIS, you can download this issue for free as a pdf. Print copies are available in our online store.
This is a false color image of a mosaic of Mercury.
Click on image for full size
Courtesy of NASA.

Discover Mercury

Mercury's orbit is so close to the Sun that it is difficult to see by ground-based observers. This explains why some early astronomers never saw the planet. Viewed from Earth, Mercury is never far from the Sun in the sky. Because of the glare of the Sun, it can only be seen in twilight.

Timocharis made the first recorded observation of Mercury in 265 BC. Other early astronomers that studied Mercury include Zupus (1639), who studied the planet's orbital phases, and Schorster and Harding (1800) who studied the very faint surface markings on the planet visible from Earth.

Because it is so difficult to make out features on the surface of the planet from Earth, it was not until the 1960s that scientists determined the correct rotation rate (59 Earth days) of the planet on its axis. This also showed that Mercury's rotation period and orbital period are in resonance.

The one and only space mission to visit Mercury was Mariner 10, which passed by the planet three times in 1974. Images taken by Mariner 10 are the only close up images we have of the planet's surface. However, NASA has recently revealed a new mission to Mercury. Messenger (the Mercury Surface, Space Environment, Geochemistry and Ranging) will begin its journey to the small planet in 2004

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF