http://apod.nasa.gov/apod/ap090308.html
I was thinking last night about the recently launched Kepler...
The earth orbits once every 365 days at a distance of 107 solar diameters.
Europa orbits once every 3.55 days at a distance of just 5 Jupiter (polar) diameters.
Hence a distant Kepler observing our solar system would have
21 times better chance
of being in alignment to see Europa transit Jupiter than seeing the Earth transit the Sun...
and it would occur
100 times more often.
I wonder whether a distant (next generation) Kepler could detect the loss
of a bright gibbous Europa (albedo ~ 0.67) ducking behind Jupiter
or the even more likely probability of being eclipsed by Jupiter.
Better still, if Jupiter were 5 times closer to the Sun then a cloudy gibbous
water Europa (albedo ~ 0.36) would be ~10 times brighter still (vis-a-vis the sun).