This Day in History, 1984: Transit of Earth from Mars
On May 11, 1984, twenty-one years ago today, an astronaut standing on the surface of Mars would have seen the Earth transit the Sun. A transit takes place when a planet passes directly between the Sun and an observer, as happened with the planet Venus for those of us on Earth on June 8, 2004. (Friends may recall that Nomi and I went to the Harvard-Smithsonian to observe the Transit of Venus, which Nomi wrote about in her LiveJournal. Her entries can be found here; my own entry merely referred people to hers.)
No one has ever seen a transit of Earth from Mars, but in 1971 Arthur C. Clarke published a science fiction story called "Transit of Earth," in which a doomed astronaut on Mars does in fact observe the 1984 transit. Needless to say, the story was rather optimistic about the pace of human exploration of the solar system.
The next transit of Earth from Mars will occur on November 10, 2084. Buy your tickets now!