Starting from the left is Mercury the inner-most planet. The only spacecraft ever to visit Mercury was Mariner 10 which first flew past the planet on March 29, 1974. Next to Mercury is Venus. This image of Venus was also taken by Mariner 10 while on its journey towards Mercury. The image was acquired on February 5, 1974.
Earth comes third in line.
This picture of Earth was taken by the Apollo 17 astronauts in December 1972. Mars has always attracted the interest of mankind and has been visited by a number of spacecraft. This particular picture was created from a Mosaic of numerous images taken by the Viking spacecrafts. The outer row of planets includes the gas giants - Jupiter, Saturn, Uranus, and Neptune. All four of these images were acquired by the Voyager spacecrafts.