Flamsteed Astronomy Society
I wonder ......
...if you were to stand on Mars, could you watch a Transit of Earth?
Mike Dryland writes -
“At the Transit of Venus event in Greenwich on June 8, a visitor asked me if Transits of the Earth would be visible if you could stand on Mars, Jupiter or any of the outer planets. How long would you have to wait? I knew in theory that an Earth Transit would take place sometime from the viewpoint of the outer planets but it seemed like a good question as to if it would be visible and when.”
Tony Sizer at the ROG replied -
“To see a Transit of Earth you could stand on any outer planet, but Mars is the only one of any practical importance as the other planets are so far away that the Earth would appear very small from them.”
Mike checked out the Astronomy.com reference which quotes copious data on the dates of Earth transits.
From Mars, an Earth transit would have been visible in 1984 on May 11. The next one will not be visible until 2084 on November 10, so there is at least an evens chance of it being witnessed by some intrepid traveller! In 1971 Arthur C. Clarke published a story called “Transit of Earth” foretelling such an event.
From Jupiter, the previous happened in 2002 on January 1. The next will be in 2008 on July 9, and 2014 on January 5, but one doubts they will be naked eye events in any sense.
From Saturn the next will be in 2005 on January 13, and 2020 on July 20.
Earth and Moon from Mars imaged by Mars Global Surveyor (NASA/JPL-Caltech)