Mercury Spotting . ... Credit Copyright: SOHO - EIT Consortium , ESA , NASA Explanation: Can you spot the planet? The diminutive disk of Mercury, the solar system's innermost planet, spent about five hours crossing in front of the enormous solar disk yesterday (Wednesday, May 7th), as viewed from the general vicinity of planet Earth. ... Seen as a dark spot , Mercury progresses from left to right (top panel to bottom) in these four images from SOHO's extreme ultraviolet camera. ...