unstable orbit
71Scattered disc — The scattered disc (or scattered disk) is a distant region of the Solar System that is sparsely populated by icy minor planets known as scattered disc objects (SDOs); a subset of the broader family of trans Neptunian objects (TNOs). The scattered …
72Climate of Mars — Mosaic image of Mars as seen by Viking 1, 22 February 1980 The climate of Mars has been an issue of scientific curiosity for centuries, not least because Mars is the only terrestrial planet whose surface can be directly observed in detail from… …
73atmosphere — atmosphereless, adj. /at meuhs fear /, n., v., atmosphered, atmosphering. n. 1. the gaseous envelope surrounding the earth; the air. 2. this medium at a given place. 3. Astron. the gaseous envelope surrounding a heavenly body. 4. Chem. any… …
74subatomic particle — or elementary particle Any of various self contained units of matter or energy. Discovery of the electron in 1897 and of the atomic nucleus in 1911 established that the atom is actually a composite of a cloud of electrons surrounding a tiny but… …
75physical science, principles of — Introduction the procedures and concepts employed by those who study the inorganic world. physical science, like all the natural sciences, is concerned with describing and relating to one another those experiences of the surrounding… …
76Groups of minor planets — An asteroid group or minor planet group is a population of minor planets that have a share broadly similar orbits. Members are generally unrelated to each other, unlike in an asteroid family, which often results from the break up of a single… …
77List of fictional elements, materials, isotopes and atomic particles — This list contains chemical elements, materials, isotopes or (sub)atomic particle that exist primarily in works of fiction (usually fantasy or science fiction). No actual periodic elements end in ite , though many minerals have names with this… …
78Stars and planetary systems in fiction — The planetary systems of stars other than the Sun and the Solar System are a staple element in much science fiction. Contents 1 Overview 1.1 The brightest stars …
79Exploration of Mercury — The exploration of Mercury has taken only a minor role in the space interests of the world. It is the least explored inner planet.JHU/APL (2006). [http://messenger.jhuapl.edu/ MESSENGER: MErcury Surface, Space ENvironment, GEochemistry, and… …
80moon — mooner, n. moonless, adj. /moohn/, n. 1. the earth s natural satellite, orbiting the earth at a mean distance of 238,857 miles (384,393 km) and having a diameter of 2160 miles (3476 km). 2. this body during a particular lunar month, or during a… …
