NASA has just released more images of Mercury as seen by the MESSENGER spacecraft, and they're pretty cool:
This first one is something of a repeat, showing the same region as the picture they released yesterday, but now it's in color! Mercury is not exactly the most beautifully hued planet, but it does have some color to it. This composite was taken in the infrared (shown red in the image), red (shown as green in the image) and blue (shown as blue), and has a maximum resolution of about 2.7 kilometers (1.6 miles) per pixel. While most of the surface looks gray, look again: some of the craters do show subtle color variations. This is most likely due to the material excavated on impact -- composition, particle size, and other factors change the way these features reflect light. This image only uses three colors, but the wide angle camera haseight 11 filters, which will allow planetary scientists to map the planet very effectively and learn about the composition and history of the surface. Sometimes, the false colors really make a difference, like in this color close-up of a crater field near Hokusai. Funny -- this image uses the same filters as in the first image above, but this region happens to have more color. That's likely due to variation in mineral composition across the area, which is on average more diverse than in the much larger field of view above.
Anything white in the image reflects all light equally, but something blue means that the material absorbs redder light and reflects blue. Olivine (a very simple mineral found everywhere in the solar system), for example, behave that way, so we may be seeing an abundance of them in that one blue crater. Better, more detailed observations will make this clearer. Images like this show scientists where to follow up, with the crater's color essentially announcing something interesting is going on there.
Of course, I do like the splashy, wide-angle shots too:
This shot of the horizon is simply lovely. You can see the long, linear rays from the crater Hokusai, which practically envelope the planet. Other fresh craters can be seen as well. Pictures like this from MESSENGER may become more rare as the science observations concentrate on high-resolution data, which means looking more toward "straight down" from the spacecraft's viewpoint, as opposed to features farther away on the horizon.
But there's a terrible beauty in all these pictures. Mercury is a strange little world. Hot, dense, battered, cracked... it's as unlike Earth as any solid body can be, and it's exactly those contrasts that will help us understand more about planetary geology and environments. We travel the solar system for many reasons -- to learn about strange, new worlds; to discover new science; to have our brains tickled at the wonder and majesty of nature -- but it's funny how so many of these findings wind up helping us understand our own planet. That may not be the only reason we go, or even the most important one, but it's still a fine thing to do.
Images credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington