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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 false color image of a mosaic of Mercury.
Click on image for full size
Courtesy of NASA.

Evolution of Mercury

Mercury, like the other planets, is believed to have formed in the earliest stage of the evolution of the solar system as dust came together to form even larger clumps and eventually small planets or "planetesimals". Eventually, the largest clump's pull of gravity "swept up" the remaining smaller clumps, producing craters on the young planet's surface. Because Mercury is so close to the Sun, many of the lightest elements in the original solar dust cloud were probably not plentiful in the innermost solar system. As a result, the material left to form the planet was rich in metals and other elements and minerals that are solids at high temperature. Under the influence of gravity, the planet continued to shrink, eventually melting much of the planet and allowing separation of materials by their density. Sinking of the heaviest elements to the center of the planet led to the formation of an iron-rich molten core. Movement of this molten metal in Mercury's interior is probably responsible for the magentic field Mariner 10 measured at Mercury. The planet cooled quickly, because of its small size, and it probably has a thick rocky layer or "lithosphere" extending hundreds of km into the planet from the surface - possibly even to the core. As the planet continued to cool, it shrunk slightly, causing compression of the surface and eventually thrust faults, where one portion of rock slips up to partially cover another. These thrust faults are probably responsible for the formation of wrinkled ridges which were observed by Mariner 10.

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Science, Evolution, and Creationism

How did life evolve on Earth? The answer to this question can help us understand our past and prepare for our future. Although evolution provides credible and reliable answers, polls show that many people turn away from science, seeking other explanations with which they are more comfortable....more

Mariner 10 Mission to Mercury

The Mariner 10 mission (USA) to Mercury was launched on November 3, 1973 and arrived at Mercury on March 29, 1974. The spacecraft made three separate passes by the planet, and obtained about 10,000 images...more

Wrinkle Ridges

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

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

Structure of Mercury's Interior

Mercury has a radius of 2439 km (1524 mi), and the metallic iron-nickel core is believed to make up about 75% of this distance. Measurements of the planet's magnetic field made by Mariner 10 as it flew...more

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 location across...more

Evolution of Mercury

Mercury, like the other planets, is believed to have formed in the earliest stage of the evolution of the solar system as dust came together to form even larger clumps and eventually small planets or...more

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 in the early formation of the solar system. We only know what half of the...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