Natural, silica-rich, homogeneous glasses produced by complete
melting, and dispersed as droplets during terrestrial impact events.
Tektites range in color from black or dark brown to gray or green and most
are spherical in shape. They have been found in four regional deposits
or strewn fields on the Earth's surface: North America,
Czechoslovakia, Ivory Coast and Australasia.
Included in this group are the planets Mercury, Venus, Earth, and Mars. They are classified as terrestrial planets because of there compact, rocky, Earth-like appearence.
The gravitational pull on planetary objects from nearby planets and moons. When the tidal forces of a planet and several moons are focused on certain moons, particularly if the orbits of the various objects bring them into alignment on a repeated basis, the tidal forces can generate a tremendous amount of energy within the moon. The intense volcanic acivity of Io is the result of the interaction of such tidal forces.
The frictional heating of a satellite's interior due to flexure
caused by the gravitational pull of its parent planet and possibly
neighboring satellites.
Satellites which orbit at the Lagrangian points, 60° ahead
of and 60° behind another satellite. For example,
Telesto and Calypso
are trojans of Saturn's satellite
Tethys.
The lower regions of a planetary atmosphere where convection keeps the gas mixed and maintains a steady increase of temperature with depth. Most clouds are in the troposphere.
