Terrestrial Planets

The Terrestrial planets show a fantastic diversity in their physical properties, surface morphologies, thermal histories and other properties. Except on the Earth, with its highly active system of convectively driven plates, the role of cosmic impact is strong or dominant.

Studies

The Messenger mission to Mercury is the first to orbit the planet and reveal its full surface at high resolution.  Mercury is extraordinary in having polar ice deposits while being the planet closest to the Sun.  Its high density indicates the presence of a massive iron core.  Measurements from Earth and from orbit are throwing light on its interior structure. (Jean-Luc Margot, David Paige)
Venus is Earth’s twin in terms of mass and radius but in many other respects is completely different from our planet.  For example, it has no organized magnetic field, no moon, its atmosphere super-rotates and appears to be influenced by tides from the Earth, its surface is very hot (700K) owing to the greenhouse effect, there is almost no water and the surface appears to be only 500 Myr old.  UCLA researchers study the dynamics of its massive carbon dioxide atmosphere.  (Jonathan Mitchell, Jerry Schubert, Chris Russell)
Mars is a focus of study because of its relatively benign physical conditions, geological evidence for the flow of water across the surface in the past, and the possibility that Mars might have been a habitat for life.  Additionally, some features on Mars can be interpreted in a plate-tectonics context (An Yin).