By Tim Lambert
The Observation of Mercury
Mercury is named after the messenger of the Roman gods. Mercury is visible to the naked eye and it has been known since Ancient Times. In the early 17th century Galileo observed Mercury through his telescope. In 1631 Pierre Gassendi became the first man to observe a transit of Mercury across the Sun. Then in 1639, a man named Giovanni Zupi showed that Mercury has phases like the Moon and Venus.
In the late 19th century the Italian astronomer Giovanni Schiaparelli suggested that a ‘day’ on Mercury lasts 88 days the same time it takes to orbit the Sun. That would mean one side of Mercury is always facing the Sun and one side is always facing outwards into space. However, he was wrong. In 1934 a Greek astronomer named Eugenios Antoniadi published a map of Mercury.
Then in 1962 Russian scientists bounced a radar signal off Mercury. American scientists followed in 1965 and they showed that a ‘day’ on Mercury is only 59 days, less than its ‘year’ of 88 days so the idea that one side always faces the Sun is incorrect.
Probes to Mercury
In March 1974 the American probe Mariner 10 flew past Mercury. In 2011 the Messenger probe reached Mercury. It went into orbit around the planet and mapped its surface. In 2015 the Messenger probe crashed into the surface of Mercury. The European Space Agency is planning to launch a probe called BepiColombo in 2016. It will reach Mercury in 2024.
The planet Mercury has appeared in many science fiction stories. Mercury appeared in the story Runaround by Isaac Asimov (1942) and Out of the Sun by Arthur C Clarke (1958). It also appeared in Mission to Mercury by Hugh Walters (1965).
Last revised 2020