A small satellite of Saturn, discovered in 1980 when the planet’s rings were edge-on and thus invisible as viewed from Earth. It is co-orbital with Tethys and Calypso.

Pertaining to the Earth. In astronomy, telluric lines are spectral lines in the spectrum of an astronomical object caused by molecules in the Earth’s atmosphere.

The boundary between the illuminated and unilluminated portions of the surface of a planet or moon.

An extensive land mass on a planetary surface. The lighter-coloured highland areas of the Moon are sometimes called terrae in contrast with the darker mare areas.

Pertaining to the Earth.

dynamical time.

One of the inner rocky planets Mercury, Venus, Earth and Mars, which are similar in fundamental structure to the Earth, in comparison with the jovian planets.

A term used in the naming of areas on the surface of Venus that show polygonal patterning.

A satellite of Saturn discovered by Giovanni Cassini in 1684. Its low density, only 1.1 times that of water, suggests that at least half of the interior must be ice. Images from the Voyager spacecraft show the surface to be heavily cratered, though there are regions of lower crater density, indicating that geological activity resulting in resurfacing took place in the past. Two notable features are the crater Odysseus, which is 400 kilometres 250 miles in diameter, and Ithaca Chasma, a valley more than 2,000 kilometres 1,250 miles long that cuts round three-quarters of the satellite’s circumference. It is 100 kilometres wide and several kilometres deep. Tethys’s orbit is shared by two very small satellites, Telesto and Calypso.

A satellite of Neptune 1989 N5 discovered during the flyby of Voyager 2 in August 1989.

A raised volcanic area on Mars, 10 kilometres 6 miles above the datum level for the planet. Three large volcanoes, rising to 27 kilometres 17 miles above the datum level, lie in a line along the ridge. They are Arsia Mons, Pavonis Mons and Ascraeus Mons.

rotation axis to sweep out a complete cone in space as a result of precession.

A small satellite of Jupiter number XIV, discovered by S. P. Synnott in 1980.

Asteroid 24, diameter 228 km, discovered in 1853 by A. de Gasparis. It is the prototype of a Hirayama family of C-type asteroids whose orbits have semimajor axes of 3.13 AU.

One of the Hirayama families of asteroids, located at a distance of 3.13 AU from the Sun. The members of the family are all of the carbonaceous type, suggesting that they all come from the same parent body.