There are three stages involved in exploring a planet; these are a flyby, orbit and landing. The first attempt at a flyby was an unnamed russian mission luanched on October 10th 1960, this any many of the following missions launched by the USSR failed.

The first flyby attempt made by the USA was Mariner 3 which was launched November5th 1964 and also failed to complete its mission. 23 days later Mariner 4 was launched and on the 14th of July 1965 achieved the first successful flyby of Mars. Mariner 4 managed to return 21 photos of the planets surface. In 1969 Mariner 6 and 7 were launched and achieved the first dual mission to Mars, during July and August of that year they collected 201 pictures of he Planets surface. The pictures of the surface squashed theories from the 1800s that dark features visible from earth (with use of telescope!) were canals containing water.

The USSR continued to have little success with their Mars missions and it wasn't until 28th May 1971 that Mars 3 was launched and preceded to collect any data. Mars 3, a Russian spacecraft was in fact the first spacecraft to land on Mars. However the craft stop transmitting data only minutes after landing.

Mariner 8 & 9 were designed by NASA to orbit Mars, Mariner 8 failed during launch however Mariner 9 was successfully launched On the 30th May 1971. Mariner 9 became the first spacecraft to achieve orbit over Mars returning 7329 photos.

1973 saw the USSR launch four more missions including Mars 4,5,6 & 7, though they returned little data.

In 1975 NASA triumphed again with the launch of Viking 1 on the 20th of August and Viking 2 on the 9th of September. The Viking craft consisted of orbiters and landers, Viking 1's orbiters stayed in orbit until 1980 and Viking 2's until 1987. Viking 1's lander touched down on the 20th of July 1976 and Viking 2's on the 3rd of September 1976. The Viking mission was hugely successful and collected over 50,000 photos of Mars.

Few missions were launched during the 1980s and early 1990s and it wasn't until 1996 that NASA achieved another highly significant achievement.

Launched December 4th 1996 Mars Pathfinder landed on the surface of Mars July 4th 1997, American Independence Day. The mission is most famous for the robotic rover that it delivered to the surface of the planet. The mission was a triumph returning more than 17,000 images (from the lander and the rover), extensive data on rocks, soil and weather as well as demonstrating the abilities of robotic rovers for space exploration.

A year later on the 4th July 1998 Japan launched its first spacecraft bound for Mars. Nozomi also known as Planet-B is designed to orbit mars however a problem with the propulsion system means it won't arrive until December 2003.

1999 saw the lost of both NASA's Mars Climate Orbiter and Mars Polar Lander. NASA's Mars Odyssey, launched 7th April 2001 is currently in orbit conducting its prime mission of science mapping.

A historical log of all missions to mars as well as detailed descriptions can be found on NASA's site at the following address

http://mars.jpl.nasa.gov/missions/index.html

Another timeline can be found at the BBC's science website at the following address

http://www.bbc.co.uk/science/space/exploration/missiontimeline/index.shtml