Both ice and organic materials, which are similar to tar or coal, were believed to have been delivered millions of years ago by comets and asteroids crashing into the planet. “It’s not something we expected to see, but then of course you realize it kind of makes sense because we see this in other places,” such as icy bodies in the outer solar system and in the nuclei of comets, planetary scientist David Paige, with the University of California, Los Angeles, told Reuters.
Unlike NASA’s Mars rover Curiosity, which will be sampling rocks and soils to look for organic materials directly, the MESSENGER probe bounces laser beams, counts particles.