Elysium Planitia (Released 16 August 2004)

On Earth, landforms like rivers and mountains are given names. Thenames identify a specfic location and also tell the type of landform;for example: Mount Everest, the Amazon River, the Pacific Ocean.Landforms on other planets and large moons of our solar system arealso given names that denote the type of feature and the individuallocation. It is much easier to discuss the largest volcano inour solar system by using its name (Olympus Mons) rather than its map coordinates (Mars, 32N latitude, 135W longitude).There are strict rules and conventions for assigning landformnames to solar system bodies. The International AstronomicalUnion (IAU) is in charge of approving or disapproving submittednames. The online directory of all (non-Earth) planetary namesis located at http://planetarynames.wr.usgs.gov. The directorycontains information on feature descriptors (Mons = mountain)and categories of names for feature types (valleys on Mars arenamed for the word "mars" in different languages). The listof descriptor terms can be found at http://planetarynames.wr.usgs.gov/append5.html. Mythologies of different cultures are often used in selecting names; names on Mars are primarily from Greek/Roman mythology, while names on Callisto (a large moon of Jupiter) are from Norse mythology.As new data is collected for a planetary body, old names mayundergo change. Location names like Olympus are retained, although the lat/long location may be shifted. The usual changeis in the descriptor type. Better images may show that a differentdescriptor gives more accurate information about the landformtype; for example, what previously looked like a featurelessplain (planitia) in higher resolution is shown to be a hugeset of lava flows (fluctus). The THEMIS images shown here willillustrate how some Mars names may need to be updated, whileothers are still very accurate descriptors of the landforms.Elysium Planitia

• Planitia: low plain
• Elysium: the Elysian fields. The Elysian fields are a paradise where the chosen of the gods reside after death; the heaven of heroes.

Elysium Planitia is located south of Elysium Mons, a large volcano. Multiple lava flows are evident in the daytime IR image. There are also small hills and craters of various sizes.Nomenclature Fact of the Day: Names with political, military, or religious significance are not allowed, except for names of political figures prior to the 19th century.