The orbital elements describing the instantaneous, purely elliptical orbit of a body subject to perturbations. If the perturbing influences were to disappear at some particular time, the body would continue to follow an orbit described by the osculating elements for that moment in time.

Abbreviation for Orbiting Solar Observatory.

The planets beyond the asteroid belt, namely Jupiter, Saturn, Uranus, Neptune and Pluto.

A channel on Mars, typically several kilometres wide and hundreds of kilometres long, that once drained large amounts of liquid water from the southern uplands to the northern lowlands.

The release of gas, possibly creating an entire atmosphere, from the surface material of a planet.

The radio astronomy observatory of the California Institute of Technology Caltech, located 400 kilometres 250 miles north of Los Angeles at an altitude of 1,200 metres 4,000 feet. The instruments there are a five-element radio interferometer which includes two 27-metre 88-foot dishes, dating from 1960, a 40-metre 130-foot dish built in 1965 and a millimetre-wave interferometer consisting of three 10.4-metre 34-foot dishes. The interferometer is used particularly for solar observation and the 40-metre dish is used for very-long-baseline interferometry.

A planetary nebula in the constellation Ursa Major. It is one of the largest planetary nebulae known, with a diameter of 1.5 light years, and lies at a distance of 1,600 light years.

Project Ozma.

A form of molecular oxygen containing three atoms instead of the normal two. It is created by the action of ultraviolet light on air or oxygen. A layer of ozone in the Earth’s upper atmosphere at a height of about 25-40 kilometres 15-25 miles serves as a protective barrier against ultraviolet light from the Sun, which is harmful to life.