It's looking likelier that there is an undiscovered planet orbiting beyond the Kuiper belt. If it's there, it's roughly 10 times the mass of Earth (or about half the mass of Neptune), likely never gets closer to the Sun than about 100 AU, and takes more than 10,000 years to orbit the Sun.
Tomorrow, Cassini will fly by Titan, picking up a gravity assist that will tilt its orbit slightly up and out of the ring plane. That will end what has been a wonderful year of frequent encounters with Saturnian moons.
It's official: China plans to send a lander mission to the lunar farside. A relay satellite will launch to the Earth-Moon L2 point in June of 2018, and a lander will follow at the end of 2018. The landing site may be within the south pole-Aitken basin.
Juno is now fewer than six months and 100 million kilometers away from Jupiter, and the Juno team is busily preparing for the arrival. Amateur astronomers are supporting them by taking lots of Jupiter photos.
In the six weeks since my last detailed Curiosity update, the rover has driven to, on, and around a couple of active barchan sand dunes on Mars. They are now searching for a site to scoop and sample sand on the western edge of Namib dune.
One of the great things about NASA is that all the data returned from all of the missions all over the solar system belong to you, the public. NASA shares all these data, and more, through the Planetary Data System, the Minor Planet Center, the Astromaterials Office, and the Astrogeology Science Center.
How many planetary exploration missions are there, and where are they? These days, it's hard to keep track, because there are so many. I plan to begin the new year by taking stock of active missions, figuring out what each has set out to do and accomplished so far, but first I want to step back to consider the spread of missions across the solar system as a whole.
Europe's second mission to Mars has begun its journey from its birthplace in Cannes to its planned arrival at Mars on October 19. Since December 17 we've been able to watch every step of its journey via Twitter.