Glossary term: Mercury

Description: Mercury is the closest planet to the Sun at a distance of about a third of the Sun–Earth distance and completes its orbit in 88 days. Among the eight major planets, Mercury is the smallest with a radius of about 2500 kilometers, which is slightly larger than our Moon. Due to its close distance, the Sun is seven times brighter seen from Mercury, and Mercury's surface is much affected by the solar wind. Its very thin exosphere is made of material produced by this interaction, plus matter blasted off the surface due to frequent falling objects. The thin atmosphere cannot keep the planet's temperature, so the surface is extremely cold (-180 degrees Celsius) during the night, and extremely hot (400 degrees Celsius) during the day, and thus very dry.

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Term and definition status: This term and its definition is still awaiting approval

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".

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The planet Mercury covered by many craters


Caption: This image is a composite of a picture mosaic of the planet Mercury's surface obtained by the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) space probe. MESSENGER was launched by NASA in 2004 and explored Mercury from 2011 to 2015.
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington credit link
License: PD Public Domain icons