A lonelier solar system
For now, the Jupiter probe Juno is our lone craft in the “second zone” of our solar system, which contains the gas and ice giant planets and their approximately 170 moons. Juno is expected to meet a controlled destruction into Jupiter next year. There are rumblings of missions to Uranus and Neptune, but those are decades away. The Voyager crafts, weakly functioning but still alive, are speeding out of our solar system as fast as they can go, tasting the constituent particles of interstellar space. New Horizons is skimming through the Kuiper Belt toward a primordial body called 2014 MU69. In other words, what’s left out there isn’t staying put.
Sometime in the 2020s, the Europa Clipper will, with all hope, arrive in the Jupiter system and detail its four massive moons, focusing on the ocean beneath Europa. Ganymede is believed to have an ocean as well, something the craft may confirm. But any plan to return to the Saturn system is far off and likely to focus on Enceladus and Titan — there are at least three proposals to explore these worlds. This may leave some of the other fascinating moons like Dione, another ocean world, in the dust.
Cassini's last dedicated images of Enceladus' plumes, taken August 28 over the course of 14 hours.
NASA/JPL-Caltech/Space Science Institute
Cassini’s final moments left us with parting pictures of Enceladus and Titan, new studies of the rings and a phenomenon called “ring rain,” and spectacular details of the upper atmosphere of Saturn before it met its demise, ripped apart and burned up by Saturn’s atmosphere in a space of about two minutes. But it was out of fuel and NASA couldn’t risk it colliding with an ocean world and contaminating it with Earth bacteria.
For now, the outer solar system is a lonely place. With all luck, we will be back soon enough.