Europa rising above Jupiter’s cloud tops at 11:48 UTC on 28th February, six hours after the New Horizons spacecraft’s closest approach to the giant planet.
It's longer than usual since I've checked the NH site; this image was posted on 1st May. A summary of a NASA Science Update given then, and lots of pretty and informative pics, are also posted.
New Horizons is a small probe --- inevitably described as being the size and roughly the shape of a grand piano --- which was put on a big rocket and flung towards to outer solar system to finally visit Pluto and, we hope, some other residents of the Kuiper Belt. It was actually thrown towards a precise rendezvous with Jupiter, passing just behind that planet to pick up speed on its way. (This now-standard technique for getting around the solar system is nicely discussed in the gravity assist page at the website of another spacecraft, Cassini.) The encounter has been used as a trial run for the Pluto encounter, and to do work in the Jovian system, which has been without its own orbiter since the Galileo mission was spectacularly wound up in September '03.
The NH site states that this picture "was one of a handful of the Jupiter system that New Horizons took primarily for artistic, rather than scientific, value."
Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute