• NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

The image is the first of many expected to come from the Messenger probe, the first space mission to orbit the planet closest to the sun. The Messenger spacecraft launched on August 3, 2004, and after flybys of Earth, Venus and Mercury, started its historic orbit around Mercury on March 17.

This is not totally unrelated, but the image and story brings to mind a not-so-new idea by Thomas Gold. The idea is this: Because much of life on earth is deep in the ground, surficial life, life above ground might be the exception. The chances of life thriving in the ground is bound to be greater than the chances of life thriving on a surface. Life on the surface is likely limited to planets that are at the right distance from a star and other such factors. Life in the ground, which draws its energy from the core, is liberated from the constraint of location, the slim window of opportunity. All it needs is a world with water, heat, and rock. This is not saying there is life on Mercury. It's just something that came to mind while looking at the photo of that planet's stark surface.