Geoff, Shenfield asked:
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 itís 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 - Scientists did see the first Martian shooting star in recent years because one of the pictures taken by one of the bodies, one of the Orbiters, on the surface of Mars showed a lovely shooting star in one of the frames which was reported in one of the science journals.
Yes, Very occasionally as we are 1.5 hundred million km from sun and mars is 2.28 so it will just depend on the elliptical orbits. We are in conjunction with mars about once every 2 years according to my science data book. So move to mars now and check it out!
Wikipedia has an article on this very subject.