Like all boys growing up in the early sixties, I was fascinated by space exploration. I watched all of the films made by the Americans and Russians showing first satellites, then animals and finally astronauts being catapulted into the cosmos. And, of course, I wanted to be an astronaut!
Space travel became more and more daring as the race to land the first man on the moon became more frantic.
But the most incredible journey taken by mankind is unmanned and is so long that it actually has no end.
A young student working at NASA in 1964 chanced upon the discovery that, in the very near future, a “grand tour” of our solar system could be undertaken. The larger planets in our solar system would be aligned so that, if a space ship could be sent to Jupiter, the gravitational pull of the planet would cast it out towards Saturn, rather like an enormous slingslot. As it flies by the planet the gravity both accelerates the spacecraft and bends its flight path. When it arrives at Saturn, the same thing would happen and the space ship would be catapulted on towards Uranus and then also on towards Neptune. The craft would then carry on and eventually disappear out of our Solar System. The alignment of the planets would be such that the distance between any two planets was, relatively speaking, a short distance. This alignment only happens every 176 years and the time when this journey could be made was fast approaching.
It was decided to launch two space craft to do just this. Voyager 2 was launched during August 1977 and was to undertake this “grand tour”. Voyager 1 was launched two weeks later on a slightly different course that would take it close to Jupiter and Saturn. This would miss Uranus and Neptune but would leave our Solar System before Voyager 2. Both Voyager craft were expected to last just four years, yet 35 years later they are still working.
The photographs and other scientific data transmitted from the Voyager craft exceeded the expectations of all concerned. Particularly striking were the photographs sent back of the major moons of Jupiter – Europa, Ganymede, Io and Callisto. These moons were not just inert lumps of rock orbiting around Jupiter. Europa, with its covering of thick ice, was found to have oceans underneath the 2 mile thick ice crust made of water, and is the only other body in our solar system where life may possibility exist. Io is the most volcanically active place in our solar system, with at least 8 active volcanoes, throwing plumes of smoke and ash miles from its surface. Io is so close to Jupiter that the gravity is stretching and squeezing the moon rather like we would squeeze a stress ball! There is a constant static electrical discharge of three million amps to the surface of Jupiter, causing storms on the surface of the gas giant. This is not a world that we would be able to exist on. Ganymede is the largest moon in our Solar System and is larger than the planets Mercury and Pluto. Callisto, with a surface of ice and rock, is the most heavily cratered of any moon in our Solar System and is thought to have vast quantities of water underground.
The giant red spot on the surface of Jupiter was studied and is in fact a large storm, three times the size of the Earth racing around the surface of the planet. The magnetic field around Jupiter stretches out 7 million miles, which makes it the largest object in our Solar System.
The spacecraft travelled on towards Saturn, with its ring system and this was a particular area of study. There are two “shepherd” moons that keep the rings together and in the same plane. Very diffuse rings and “spokes” (neither detected from Earth) were also found by Voyager. Saturn is the only planet less dense than water. In the unlikely event that a lake could be found large enough, Saturn would float in it. Titan is the only moon in the solar system known to have an extensive atmosphere. The chemistry in Titan’s atmosphere may resemble that which occurred on Earth before life evolved.
At this point the two Voyager craft took different paths; Voyager 1 headed out of our Solar System and Voyager 2 moved to Uranus and Neptune before also heading for the edge of our Solar System.
Both Voyagers have now travelled through an area called the heliopause, which marks the extent of the solar wind from our Sun, and hence our Solar System. The particles of energy emitted by the sun slow down rapidly in this area to below subsonic speeds, creating a termination shock. They are now in interstellar space, the only human-built objects ever to do this. At the time of writing they are 120 times further away from our Sun than the Earth and travelling further away at about a million miles per day. They are still sending information back to the Earth – this information takes some 16 hours to reach us and is some 20 billion times weaker than the power of a digital watch battery! The Deep Space Network has an array of dishes that capture the data sent from these distant objects. They will continue to send us data for some years before the reactors on board run out of energy.
One of the last photographs sent back from Voyager was a shot of our own Earth – the Earth is covered in just seven pixels!