A virtual sky map like this would be of interest to astronomers studying gravitational microlensing. In microlensing, the gravity of stars near the line of sight can act to magnify the light of background objects such as distant stars, or quasars. Nowhere is this magnification greater than near a gravitational lensing caustic. In the above computer simulated map, caustics are discernible as the sharp bright curved lines. When a background quasar moves across a microlensing caustic, it can appear dramatically brighter. Many astronomers thought microlensing events practically immeasurable even ten years ago, but within the past five years now hundreds have been found. Precise measurements of microlensing are now providing unique information about the composition and distribution of matter in galaxies and the universe. Some astronomers now predict that future microlensing searches might even isolate planets orbiting distant stars.

Is it an Escher, or Mars? Three different types of surfaces visible in the North Polar Cap of Mars morph into each other in a way perhaps reminiscent of the works of M. C. Escher. On the far left dark sand covers the ground, while the center shows a transition to a dune field. On the far right a transition is made to a much lighter surface, likely containing a larger amount of ice. Shadows indicate that lighter material holds the higher ground, with some steep cliffs on the divide. Dune shapes indicate that wind typically blows toward the upper left. Mars Global Surveyor, one of two robot spacecraft currently orbiting Mars, took the above image in early 2001. Recent images from the other orbiter, Mars Odyssey, have bolstered the hypothesis that a significant amount of water-ice lies beneath the surface near the Martian South Pole.