Space probes are unmanned, remote-controlled spacecraft. They are sent to explore other planets and moons—even comets and asteroids—in the Solar System. Often, they are steered to "fly by" or go into orbit around one of these worlds. Sometimes, they are landed on a planet or moon’s surface. Space probes are equipped with cameras and sensing equipment, so they can transmit information back to Earth by radio.

Voyager

The twin space probes, Voyager 1 and Voyager 2, were launched in 1977. They visited the outer planets, Jupiter, Saturn, Uranus and Neptune. The probes carried out a “fly by” of each planet, taking pictures and send back information about the planets and some of their moons. Voyager 2 captured this image (left) of Neptune's moon Triton in 1989.

Cassini

The Cassini space probe was launched in 1997. Seven years later, it arrived at Saturn. Attached to the probe was the Huygens lander. On 25th December 2004, Huygens separated from Cassini and parachuted down to the surface of Titan, Saturn’s largest moon. Over a period of 90 minutes, it then sent pictures and information back to Earth.

Titan's surface is hidden from view behind its thick atmosphere. Huygens revealed a landscape of lakes and rivers—although the liquid was not water but mostly liquid methane.

Cassini then visited another moon, Enceladus. It was carefully steered through the fountain of water vapour and ice fragments being erupted into space by ice volcanoes on the moon. It detected chemicals that may one day reveal the presence of living things in an ocean beneath Enceladus’s crust.

Cassini’s mission ended in 2017. It was deliberately destroyed by crashing it into Saturn. This was done to prevent any risk of it contaminating Saturn's moons.

Probes on Mars

There have been many space probe missions to Mars. A number have landed on the surface and released rovers, small powered vehicles, to roam the Martian landscape and take images of it. The Curiosity rover touched down in August 2012. It was designed to find out whether Mars is, or has ever been, capable of supporting life.

The Perseverance rover made its landing in Mars's Jezero Crater on 18th February 2021. It has a similar design to Curiosity. The rover is collecting rock samples which will be picked up and returned to Earth by a space probe mission planned for the future. Perseverance carried on board a mini-helicopter, named Ingenuity. It made 72 flights until it was damaged and could no longer fly.