I don't think the MESSENGER mission to Mercury ever captured the imagination of the general public in the same way Cassini is still doing at Saturn. MESSENGER ended its 11 year mission yesterday. With no more fuel aboard the spacecraft the peturbing force of solar gravity finally brought MESSENGER down with a bang on the surface. Prior to 2011 Mercury was a largely unknown planet with just one-third of its surface imaged in the 1970s. MESSENGER has transformed our view of Mercury since its first flyby in 2011 and sent back views of the planet like these:
Mercury has clearly been battered and scarred from impacts sustained since the earliest days of the solar system.
Meanwhile, on the other side of the solar system the New Horizons spacecraft is hurtling towards a July rendezvous with an ex-planet called Pluto. New Horizons is now close enough to Pluto - a world even smaller than Mercury - for its cameras to pick out surface details:
NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
The orbiting moon is called Charon and it's quite big compared to Pluto. Pluto appears to wobble because the centre of mass (the barycentre) of Pluto and Charon is some way outside Pluto. The close-up view shows a lot of variation in brightness across the disk. Clearly Pluto is going to be an interesting place to see when New Horizons eventually arrives!
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Dr Adrian Jannetta. Amateur astronomer, maths teacher and science enthusiast.