Every 26 months or so, the orbits of Mars and Earth briefly align, giving Earth-dwellers the best view of the Red Planet they're likely to get.
This near approach is happening now, with the planets reaching their closest point today at about 3:45 Pacific Time, at a distance of about 55 million miles. Over the last few days, the sharp-eyed Hubble Space Telescope has trained its cameras on the Red Planet, resulting in this nearly cloudless view of our neighbor.
The big dark triangular feature to the right is the Syrtis Major region, while the long nearly horizontal line to its left is the Sinus Meridani. The Opportunity Rover is wheeling around the planet near the western edge of this latter region.
Because of the two planets' elliptical orbits, these close approaches vary in their distance each time. Despite the clear picture, this isn't a particularly close approach – in 2003, Mars came about 20 million miles closer to Earth.