Since the 1950s, humans have sent robots and space probes all over the Solar System.
The Voyager probes have even gone beyond our Solar System into open space!
Before it left, Voyager turned its camera around and took a photo of Earth from 6 billion kilometres away. In the image, the Earth looks like a tiny pale blue dot.
The craft contains a kind of time capsule of Earth. If they are ever found, this golden record can be played to reveal sounds and images from Earth.
It is much safer and easier to send robots into space than people. They can survive difficult conditions. They can live in the freezing temperatures of outer space. They can burn when flying through a planet's atmosphere and still land unharmed on its surface.
They don't need air to breathe or food and drink. They just need energy to power them. Today, this comes from batteries and solar panels, which get energy from the Sun's light. Early space probes ran on nuclear reactions!
The first ever space probe was called Sputnik 1. It was launched by the Soviet Union in 1957. Since then, people have carried on launching robots into space.
Robots have landed on planets and moons. They have even landed on an icy comet. Not only that, but they have studied the Sun, planets and objects so small and far away that telescopes on Earth can't even see them! All to safely explore our place in space.
- Planets and Moons
Sending space probes closer to planets in our Solar System has revealed much of the details we know about them. Often, the journey to the outer planets involves lots of fly-bys of asteroids, planets, and moons, which give us a wealth of information.
The Cassini probe explored Saturn's rings, discovered storms on its surface, and spotted geysers on the icy moon Enceladus. It even sent a smaller probe, Huygens, to land on one of Saturn's other moons, Titan. Titan is one of the objects in space with an atmosphere and water, possibly able to support life.
The search for places that could support life has become a goal of many space missions, such as Juicy, which is travelling to Jupiter's moons.
Several space probes have studied Jupiter, looking at its atmosphere and magnetic fields. They have even discovered that the famous Great Red Spot, a huge storm, has started shrinking.
Mars, one of our closest neighbours in space, has been a favourite place to send space probes and robot rovers, which still roam the surface. Rovers are much more helpful than landers, which do not travel around. Rovers can cover more ground and move to interesting things.
They can also put themselves in sunny positions to charge their batteries and survive the winter. Rovers have been on the surface of Mars since the 1990s, giving us amazing photos of the surface and witnessing changes such as huge dust storms and frosty mornings.
The rovers can even drill into rocks and carry out experiments on the surface. Rovers on Mars have confirmed that the planet used to be much wetter than it is today and may once have been able to support life.
- Asteroids and Dwarf Planets
We have sent space probes into the asteroid belt to study the object and Ceres, the dwarf planet which lives there.
Asteroids are rocky, and space probes have discovered that some of the meteorites on Earth came from objects still living within the asteroid belt.
These missions want to study these objects to see how the Solar System may have formed. Ceres is icy, and the Dawn spacecraft discovered that it had liquid water under its surface and even organic materials, one of the ingredients for life.
The New Horizons probe even travelled as far as the dwarf planet Pluto. It was discovered that Pluto had extra moons called Kerberos and Styx, which were too small to be seen from Earth, even with the biggest telescopes. The probe even found a massive glacier on the surface of Pluto, the largest in the Solar system, shaped like a heart.
- Comets
Space probes, like Rosetta, have been sent to comets to study what they are made of in more detail. Comets are thought to contain the stuff left over from the very start of the Solar System. These objects travel quickly through the Solar System and are difficult to send spacecraft to, involving many complicated manoeuvres.
These missions found that the atmosphere of a comet contains organic material and oxygen gas. It also found that the water vapour from the comet was different from that on Earth - dispelling the thought that the water on Earth might have arrived on a comet.