Callisto Titan Io Ganymede
Europa Titan Io Mars
7 9 3 5
The Sagan Equation The Hoyle Equation The Hawking Equation The Drake Equation
Sputnik 1 WAC Corporal Explorer 1 V2 Missile
186 million km/second 149 million km/second 299 million km/second 93 million km/second
Jupiter Ring System Orbiting Neptune Asteroid Belt Kuiper Belt
Deimos Leda Phobos Calypso
Atlantis Enterprise Columbia Discovery
Binary planets Twin systems Double planets Biplanetary systems