That’s no moon…
And neither is it a space station. It’s the planet Mercury, viewed on approach by the Mercury MESSENGER probe. On this phase of the MESSENGER mission the probe is allowing the solar wind to push it slightly into a better approach vector; a groundbreaking application of solar sailing.
Only one other human-built probe ever visited Mercury, NASA’s Mariner 10 craft back in 1975. MESSENGER is making up for lost time. Not only will MESSENGER yield a complete image map of the surface (the first ever), it has already provided some surprises: evidence of past volcanism, new information about Mercury’s liquid core, and traces of water vapor molecules in the tiny world’s outer atmosphere (what there is of it, which isn’t much).
I’ve always had a fascination with Mercury, mainly because it’s been so ignored. It’s not a sexy planet like Mars with the potential for life, or Venus with its weird atmosphere and infernal surface conditions. Mercury just sits there, rocky and cratered. But Mercury has a lot of hidden attractions: it’s close enough to the Sun that its orbit exhibits relativistic effects, it has a magnetic field, and it’s the most heavy-metal rich world in the solar system. It’s mostly core; iron-nickel, laced with gold, platinum, rhodium, osmium, iridium, and all the other weird elements in the lower middle of the periodic table. Maybe that’s what makes it so interesting to this particular weird-element geochemist.