The New Solar System

accretion altitude Apollo asteroid belt asteroids astronomical atmosphere belt bodies bright Callisto carbon dioxide chemical chondrites cloud collisions color comets composition condensation corona crust dark density disk dust early Earth Earth-crossing Earth-crossing asteroids ejected energy Europa flow formed Galilean satellites Ganymede gases geologic gravity heat hemisphere hydrogen images impact craters infrared inner interior Jovian Jupiter Jupiter and Saturn Jupiter's kilometers km in diameter late heavy bombardment lava layer lunar magnetic field magnetosphere Mars Martian mass material Mercury meteorites methane million missions Moon nebula Neptune nitrogen objects observations occur orbit outer oxygen particles percent photograph Pioneer planetary rings planetesimals plasma Pluto polar processes radiation regions regolith result rocks rotation samples Saturn scientists solar nebula solar system solar wind space spacecraft structure sulfur sunlight surface telescopes temperature terrestrial planets tion Titan ultraviolet Uranus vapor velocity Venus Viking volcanic Voyager water ice wavelengths zonal