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With Explore the Planets, investigate the planets, their moons, and understand the processes that shape them. By G. Jeffrey Taylor, Ph.D. See our DVD collection.
This is a mosaic of the caloris basin and its surrounding area. The Caloris Basin is closest to the sun when Mercury is at the closest point in its orbit to the sun.
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The Caloris Basin

The Caloris Basin is the largest feature on the surface of Mercury. This crater was formed by the impact of a large meteorite near the end of the period of frequent impact cratering in the early solar system. We only know what half of the crater looks like, because the other half was in darkness when Mariner 10 flew by the planet. Surrounding the impact site are concentric ridges within relatively smooth plains probably brought about by renewed volcanic activity which started after the impact. On the other side of the planet, directly across from the basin, is a region initially described as the "weird" terrain, where a chaotic mix of hills and fractures is present. This may have been produced in response to shock waves which traveled to this point on the surface following the Caloris Basin impact.

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Mercury's Craters

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Surface Features of Mercury

The surface of Mercury has numerous interesting features, including a variety of craters, ridges, and terrains ranging from heavily cratered to nearly crater free. These features, and their distribution...more

Surface of Mercury

Images of the surface of Mercury obtained by Mariner 10 showed a planet covered with craters, looking very much like the Earth's Moon. During its three passes by the planet, Mariner 10 took pictures of...more

The Caloris Basin

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Wrinkle Ridges

Wrinkle ridges on the surface of Mercury are thought to have been caused by the contraction of the surface following the cooling and contraction of the core of the planet. As the core cooled and therefore...more

Evolution of Mercury

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Mercury's Interior and Surface

Mercury, the innermost planet of the solar system, is a little bigger than the Earth's Moon. The surface of the planet is covered with craters, like the Moon, but temperatures there can reach over 80...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA