Explorations of the solar system

For a long time, people have looked at the stars. Ancient civilisations, such as the Greeks and the Romans, have noticed that five objects in the sky move around. The Greeks have named these objects ἀστήρ πλανήτης(aster planetes), "wandering star". They had a name for each of the planets(Stilbon, Phosphoros, Pyroeis, Phaethon and Phainon), and gave each one a god to which it was sacred to(Hermes, Aphrodite, Ares, Cronus, and Zeus), but the Romans merely named these five after their versions of these gods(Mercury, Venus, Mars, Jupiter and Saturn). When Uranus was discovered in the 19th century, it was named after the Greek god of the sky, but Neptune was traditionally named after a Roman god, the Roman version of Poseidon.

The only planet we know that has life on it is Earth, and even though it is right under our feet, it took a long time to discover! The ancient Greeks were probably the first to find that that the world was round, more than 2000 years before Columbus. They called it Gaia.

The far side of the moon, photographed by
Apollo 16. Luna 3 was the first spacecraft
 to provide a picture of it.

Earth, as we know, has only one moon, which has a volume of approximately 1/64 of the Earth's. In 1959, the first spacecraft to fly close to the moon, Luna 1, and the first spacecraft to impact the moon, Luna 2, made their missions to the rocky world. A decade later, Neil Armstrong and his crew made the first mission to bring people to the surface of the moon. Two robotic rovers went there in the 1970s.

People have also turned their attention to Mars. The first rover that landed(Sort of, it crashed) on Mars was Mars 2, launched by the USSR in the 1970s. The Viking program was the first to successfully land and operate rovers and landers on Mars. People might be sent there sometime after 2025.

Callisto, one of Jupiter's moons.

The outer planets(Jupiter, Saturn, Uranus and Neptune) have been closely photographed by the Pioneer, Voyager, Cassini and New Horizons probes. The Voyager probes have gathered information from both gas giants(Jupiter and Saturn), and are still functioning. I will not write anything else about the Voyager probes in this post, because it is about the solar system, and they have both crossed the border into interstellar space.

In the 19th century, five new planets were discovered, Vesta, Juno, Ceres, Pallas, and Pluto. They were all named after Roman gods, due to tradition, and the first four are all in between Mars and Jupiter. These bodies were all reclassified by 2006, Vesta, Juno, Ceres and Pallas as asteroids in the Asteroid belt, and Pluto as a dwarf planet.

At July 14, 2015, New Horizons took close-up pictures of Pluto for the first time, after nine years and seven months of travel. I think these will really change peoples' idea of Pluto. The pictures show that it is yellowish in colour, and displays a big heart-shaped impression on its surface.

Above: An image of Pluto, based on pictures
 taken by the Hubble Space Telescope.
Below: The new Pluto.