The group of celestial bodies, including the EARTH, orbiting around and gravitationally bound by the sun. It includes eight planets, one minor planet, and 34 natural satellites, more than 1,000 observed comets, and thousands of lesser bodies known as MINOR PLANETS (asteroids) and METEOROIDS. (From Academic American Encyclopedia, 1983)

Any solid objects moving in interplanetary space that are smaller than a planet or asteroid but larger than a molecule. Meteorites are any meteoroid that has fallen to a planetary surface. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)

Large bodies consisting of self-luminous gas held together by their own gravity. (From McGraw Hill Dictionary of Scientific and Technical Terms, 6th ed)

The environment outside the earth or its atmosphere. The environment may refer to a closed cabin (such as a space shuttle or space station) or to space itself, the moon, or other planets.

Creation and development of bodies within solar systems, includes study of early planetary geology.

Finely divided solid matter with particle sizes smaller than a micrometeorite, thus with diameters much smaller than a millimeter, moving in interplanetary space. (NASA Thesaurus, 1994)

The behavior and interactions of matter and energy in outer space.

The science concerned with celestial bodies and the observation and interpretation of the radiation received in the vicinity of the earth from the component parts of the universe (McGraw Hill Dictionary of Scientific and Technical Terms, 5th ed)

The interdisciplinary science that studies evolutionary biology, including the origin and evolution of the major elements required for life, their processing in the interstellar medium and in protostellar systems. This field also includes the study of chemical evolution and the subsequent interactions between evolving biota and planetary evolution as well as the field of biology that deals with the study of extraterrestrial life.

Celestial bodies orbiting around the sun or other stars.

Small solar system planetary bodies including asteroids. Most asteroids are found within the gap lying between the orbits of Mars and Jupiter.

The natural satellite of the planet Earth. It includes the lunar cycles or phases, the lunar month, lunar landscapes, geography, and soil.

Aggregates of matter in outer space, such as stars, planets, comets, etc. and the properties and processes they undergo.

The fifth planet in order from the sun. It is one of the five outer planets of the solar system. Its sixteen natural satellites include Callisto, Europa, Ganymede, and Io.

Planet that is the third in order from the sun. It is one of the four inner or terrestrial planets of the SOLAR SYSTEM.

Hafnium. A metal element of atomic number 72 and atomic weight 178.49, symbol Hf. (From Dorland, 28th ed)

Large aggregates of CELESTIAL STARS; COSMIC DUST; and gas. (From McGraw Hill Dictionary of Scientific and Technical Terms, 6th ed)

Chemical and physical transformation of the biogenic elements from their nucleosynthesis in stars to their incorporation and subsequent modification in planetary bodies and terrestrial biochemistry. It includes the mechanism of incorporation of biogenic elements into complex molecules and molecular systems, leading up to the origin of life.

The solid substance formed by the FREEZING of water.

Instruments used to observe distant objects.

Devices, manned and unmanned, which are designed to be placed into an orbit about the Earth or into a trajectory to another celestial body. (NASA Thesaurus, 1988)

Stable oxygen atoms that have the same atomic number as the element oxygen, but differ in atomic weight. O-17 and 18 are stable oxygen isotopes.

Techniques used to determine the age of materials, based on the content and half-lives of the RADIOACTIVE ISOTOPES they contain.

The generic term for salts derived from silica or the silicic acids. They contain silicon, oxygen, and one or more metals, and may contain hydrogen. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th Ed)

The sixth planet in order from the sun. It is one of the five outer planets of the solar system. Its twelve natural satellites include Phoebe and Titan.

The origin of life. It includes studies of the potential basis for life in organic compounds but excludes studies of the development of altered forms of life through mutation and natural selection, which is BIOLOGICAL EVOLUTION.

Atomic species differing in mass number but having the same atomic number. (Grant & Hackh's Chemical Dictionary, 5th ed)

Travel beyond the earth's atmosphere.

A broad class of substances containing carbon and its derivatives. Many of these chemicals will frequently contain hydrogen with or without oxygen, nitrogen, sulfur, phosphorus, and other elements. They exist in either carbon chain or carbon ring form.

Stable nitrogen atoms that have the same atomic number as the element nitrogen, but differ in atomic weight. N-15 is a stable nitrogen isotope.

Isotopes that exhibit radioactivity and undergo radioactive decay. (From Grant & Hackh's Chemical Dictionary, 5th ed & McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)