Slowdown in the Outer Solar System

After Juno arrives at Jupiter, we’ll see a hiatus in missions beyond the asteroid belt.

It will be another 10 years at least before this artist's concept -- of NASA's proposed Europa mission -- becomes a reality.

Space fans have been spoiled over the past few years by a stream of exotic photos from the outer reaches of our solar system. Unfortunately, the show is about to go on a brief hiatus.

NASA’s New Horizons’ incredibly successful flyby of Pluto last July was one of the biggest stories of the year, and not just in space news. The European Space Agency’s Rosetta spacecraft and Philae lander gave us our first up-close look at a comet, and 38-year-old Voyager 1 finally reached the edge of the heliosphere. Meanwhile, the 19-year-old Cassini spacecraft—which has had two mission extensions, and has discovered, among other things, the icy plumes that signify a potentially habitable neighbor in moon Enceladus—continued to tour the Saturn system.

But Cassini, like all things, must end. The spacecraft has already made its last flybys of Enceladus and other Saturnian moons, and will spend this year performing its final flybys of Titan. The mission has a planned end date in 2017, when it will plunge into Saturn (to keep from accidentally contaminating any habitable moons in the system). As it stands now, there are no further plans to collect data directly from the ringed planet. A faction of planetary scientists, however, is pushing for follow-on projects like the Enceladus Life Finder, a spacecraft that would fly low through the moon’s geysers to detect biological organisms, if there are any. The mission was proposed for the 2015-16 round of NASA’s low-cost Discovery missions, but didn’t make the cut, which means the soonest it could go plume-diving would be the mid-2030s.

In 2016, the only new outer planets mission we have to look forward to is NASA’s Juno, which arrives at Jupiter on July 4. The spacecraft has been en route to the Jovian system since it launched in 2011, and will go into a polar orbit to study the giant planet’s gravity and magnetic fields as well as the composition of its atmosphere (and since there’s no solid surface of Jupiter, there’s a lot of atmosphere). Unless the mission is extended, Juno is expended to end its life in early 2018 by diving into the planet.

A year later, in January 2019, New Horizons will fly past a Kuiper Belt object called 2014 MU69, having traveled another four years after encountering Pluto. After that, things will go quiet in the outer solar system for a while.

Last year, however, NASA received the budgetary go-ahead for a mission to Jupiter’s moon Europa, one of the few places in the solar system, like Enceladus, where we might find active life. Congress even allocated funding for a lander, which would touch down on the icy surface. But the spacecraft will take years to build, so even with no delays, it won’t launch to Europa until the mid-2020s.

A few years ago, the European Space Agency beat the U.S. to the punch when it announced the JUICE mission (Jupiter Icy Moon Explorer), which will visit most of the Jovian system: Jupiter and three of its moons, including Europa. JUICE isn’t scheduled to launch until 2022, and won’t reach Jupiter until around 2030.  So hug your Cassini photos, it’s going to be a long wait out there in the void.

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