After Earth, Mars is the planet with the most hospitable climate in the solar system. That's because there may have been water that could have harbored primitive, bacteria-like life. There is no general agreement, however, on what form water took on the early Mars. Two competing views are currently popular in the science community. According to one theory, Mars was once much warmer and wetter, with a thicker atmosphere; it may well have boasted lakes or oceans, rivers and rain. According to the other theory, Mars was always cold, but water trapped as underground ice was periodically released when heating caused ice to melt and gush forth onto the surface.

"Life On Mars: A Definite Possibility", Aug. 21, 2004, features this image. It's made quite a few appearances over the years even though it's arguably the worst Mars pic I ever created. I created it in response to an urgent request over the weekend back in 1999 and never had a chance to make a more realistic image.