This year is going to be an exciting one, the New Horizons spacecraft will be arriving at the dwarf planet Pluto. It comes after a series of successful robotic space missions over the years including Voyagers, Pioneers, Viking, Cassini-Huygens, Galileo. But often we forget the heritage of these missions and many of them can trace their origins back to the successful Mariner program.
The Mariner program was a joint NASA/JPL initiative which ran from 1962 to 1973 and saw robotic probes sent to nearly all of the planets of the solar system. The program achieved many firsts, including the first planetary flyby, the first pictures from another planet, the first planetary orbiter, the first gravity assist manoeuvre. The total program cost was around $554 million.
Mariner 1 and 2 were 203 kg probes which performed a flyby to Venus and performed vital communications tests. They also conducted measurements of the magnetic field and solar particles. Sadly, Mariner 1 was destroyed on launch, but Mariner 2 went onto Venus for a 2.5 month successful flight. Mariner 5 was a 245 kg spacecraft that successfully performed a Venus flyby.
Mariner 3 and 4 were 261 kg spacecraft and targeted at the planet Mars. Mariner 3 was lost on launch, but Mariner 4 achieved the first successful flyby of the red planet. Mariners 6 and 7 were 413 kg spacecraft both sent to Mars for flyby missions at the equator and southern hemisphere.
By the time of Mariner 8 and 9, spacecraft mass went up to 988 kg. Mariner 8 was lost during the launch but Mariner 9 was the first spacecraft to successfully enter Mars orbit. The subsequent Viking 1 and 2 missions were built on the Mariner 9 success but were larger vehicles.
Mariner 10 was a 433 kg spacecraft which successfully conducted a flyby of both Venus and Mercury. It was the first spacecraft to use a gravity assist trajectory when going from Venus to Mercury, and the first spacecraft to encounter two planets at close range.
Mariner 11 and 12 were also planned but due to congressional budget cuts the missions were scaled back to become flyby missions of Jupiter and Saturn, and later renamed the Mariner Jupiter-Saturn probes. Later the names were changed again to Voyager missions and eventually they transitioned into the Voyager program. Other spacecraft missions also share their heritage with the Mariner probes. This includes the Magellan probe to Venus, the Galileo probe to Jupiter and the Mariner Mark II series which evolved to become the highly successful Cassini-Huygens mission which has taught us so much about Saturn and its moon Titan of liquid methane rainfall.
It is exciting to consider what missions may lie in our future, to the planets of our solar system or to objects outside it. But it is also humbling to consider the long journey we have been on, a mix of programmatic successes and failures, but we need to keep pushing onwards and never give up. For, in the end, that is how all great discoveries are made. The people behind the Mariner missions should be remembered for what they accomplished, and the foundations that they laid for the later missions we now enjoy.
Kelvin F.Long, Executive Director, i4iS