Is it possible to detect a transit of Earth across the Sun from Mars?

Dominic - It is incredibly rare for that to happen because the Earth is so much further out in the solar system than Venus. So it's a very small target that you're trying to get across the surface of the sun. I think a transit of Mercury across the surface of the sun has been seen by one of the Mars Rovers. I'm not completely sure on that, but yes, Mercury does transit the sun quite often, but Venus and Earth, much more rare.

Chris - As an aside, scientists did see the first Martian shooting star in recent years! One of the pictures taken by one of the rovers on the surface of Mars showed a lovely shooting star in one of the frames; it was was reported in one of the science journals.