Discovery and exploration of the Solar System as clouds, dust storms, and ice caps on the other planets. The first exploration of the Solar System was conducted by telescope, when astronomers first began to map those objects too faint to be seen with the naked eye. Galileo was the first to discover physical details about the individual bodies of the Solar System. He discovered that the Moon was cratered, that the Sun was marked with sunspots, and that Jupiter had four satellites in orbit around it. Christiaan Huygens followed on from Galileo's discoveries by discovering Saturn's moon Titan and the shape of the rings of Saturn. Giovanni
Mercury (planet) may appear as a bright star-like object, but is often far more difficult to observe than Venus. The planet telescopically displays the complete range of phases, similar to Venus and the Moon, as it moves in its inner orbit relative to Earth, which reoccurs over the so-called synodic period approximately every 116 days. Mercury is tidally locked with the Sun in a 3:2 spin-orbit resonance, and rotates in a way that is unique in the Solar System. As seen relative to the fixed stars, it rotates on its axis exactly three times for every two revolutions it makes around the