|One of the better photos of Mars from the 21 sent back to Earth by Mariner 4 in 1965. NASA image|
The July 14 encounter will be an exciting for me, but it will also be bittersweet, for it will mark the end of an era in space exploration. The Pluto encounter will mark the end of the first reconnaissance of our Solar System. Spacecraft have provided new and surprising information about every major body in the Solar System, including our home planet.
It all began with Sputnik orbiting Earth in 1957, and within months spacecraft like the American Explorers 1 and 3 and the Russian Sputniks 2 and 3 showed that the Earth was surrounded by a powerful magnetic field, including the Van Allen radiation belts.
Russian spacecraft struck our own moon and sent back the first photos of its hidden back side in 1959 in the opening shots of the race to the moon that culminated with American astronauts visiting a decade later.
Mariner 2 became the first spacecraft to encounter another planet when it flew by Venus on December 14, 1962.
On July 14, 1965, exactly fifty years before the New Horizons Pluto encounter, Mariner 4 flew by Mars and took the first closeup photos of that world, the first photos to be sent from another planet. Mariner 4’s primitive camera took 21 very rudimentary photos of limited portions of the Martian surface, and Mariner took more than two weeks to transmit the images to Earth.
Over the years, spacecraft visited the other planets, notably Mariner 10, which flew by Venus and Mercury in the early 1970s, and the two Voyagers launched in 1977 that visited Jupiter, Saturn, Uranus and Neptune. The Voyagers revealed the faces of the many moons that orbited these gas giants, revolutionizing our knowledge of the solar system.
Planetary flybys became big events, and as I wrote in this space last August, I was able to take part in Voyager 1’s encounter with Saturn in 1980, an event that drew media and celebrities to the control centre and helped rewrite astronomical textbooks.
After Voyager 2 flew by Neptune in 1989, only Pluto remained unseen and unvisited. Since it is so small and so distant, our best view of Pluto until a few weeks ago was a very low-definition view provided by the Hubble Space Telescope. Now the face of Pluto is being revealed to us.
Once New Horizon’s work at Pluto is done, all of the major bodies of the solar system will be known to humanity. The Solar System contains many more asteroids, moons and comets, and spacecraft will continue to reveal them to us. New Horizons itself will head to another body in the Kuiper Belt once it is done with Pluto.
That means many more discoveries await us, but the era of the first views of major bodies in the Solar System is drawing to a close. I consider myself privileged to have been a witness to that time.