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Glossary term: Terrestrial Planet

Also known as Rocky planet or telluric planet

Description: A terrestrial planet is one that is made up mostly of material such as rock and iron. Terrestrial planets lack the puffy atmosphere of hydrogen and helium found in giant gas planets, instead having much smaller atmospheres or no atmosphere at all. Terrestrial planets generally have smaller masses than giant planets and are smaller in size.

In the Solar System the terrestrial planets are Mercury, Venus, Earth, and Mars.

One of the main focuses of exoplanet astronomy has been the search for terrestrial planets of similar size and composition to Earth which lie in their star's habitable zone.

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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

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

Mercury

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


The planet Venus showing white clouds enshrouding the planet

Venus in visible light

Caption: This picture taken by NASA's Mariner 10 probe shows what the planet Venus looks like when looking at it with naked eyes. Venus is enshrouded inside a thick cloudy atmosphere dominated by carbon dioxide, never revealing its hot surface.
Credit: NASA/JPL-Caltech credit link

License: PD Public Domain icons


The planet Venus' surface with ridges and valleys

Venus' surface

Caption: This image is a computer-aided rendering of the surface of the planet Venus. Since visual light cannot penetrate the thick clouds in Venus' atmosphere, the image was obtained with radio waves. NASA's space probe Megallan, launched in 1989 mapped Venus' surface between 1990 and 1994.
Credit: NASA/JPL credit link

License: PD Public Domain icons


The Earth from space showing oceans and continents

Earth as observed from Apollo 17

Caption: Full disk view of the Earth taken on 7 December 1972, by the crew of the Apollo 17 spacecraft en route to the Moon at a distance of about 29,000 kilometres (18,000 mi). It shows Africa, Antarctica, and the Arabian Peninsula.
Credit: NASA/Apollo 17 crew/Project Apollo Archive

License: PD Public Domain icons


The planet Mars with a rusty red surface, volcanoes, valleys, craters, ice clouds and a white polar cap

Mars

Caption: This image of the planet Mars taken by NASA's Mars Global Surveyor Orbiter in 1999 shows its dry surface. The picture features the most spectacular geological regions on Mars. Besides the deep Valles Marineris valley we see four volcanoes. While three of them form the Tharsis ridge, the Olympus Mons is largest volcano we have so far discovered in the Solar System. Ice clouds cover parts of the Martian surface.
Credit: NASA/JPL/MSSS credit link

License: PD Public Domain icons

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