The Rosetta mission may be over, but the European Space Agency (ESA) has other missions to launch in years to come. These include two smaller comet proposals--Castalia and Core (Comet Rendezvous Explorer)--which will be submitted to ESA next week for consideration.

Castalia will send a spacecraft to the asteroid belt between Mars and Jupiter to probe an object that exhibits comet-like behavior. Core, on the other hand, will put a lander on another comet. But unlike Rosetta's Philae lander, which did not land as smoothly as expected over comet 67P/Churyumov-Gerasimenko, this new lander would intentionally hop from one place to another to study the varying conditions across the comet's icy surface.

According to Nick Thomas, one of Core's proposers from the University of Bern in Switzerland, they would like to maintain the Rosetta legacy.

"When Europe's Giotto probe visited Halley's Comet in 1986, it gave Europe a lead in cometary science that lasted for the next 15 years. And Rosetta is going to do the same for the next 15 years," Thomas told BBC.

"And what you do is put in a proposal now so that in 15 years' time we can send the next mission and continue that leadership."

However, if Castalia and Core will be chosen by ESA, the two missions will not launch until the late 2020s, BBC reports.

ESA's attention is now focused on the ExoMars mission, which will attempt to put the Schiaparelli lander on the surface of Mars in a couple of weeks. Schiaparelli will test the technology needed for the landing of the ExoMars rover on the Red Planet in 2021.

There is also the much-delayed BepiColombo mission, which is a European-Japanese mission to Mercury set to arrive by 2024, and JUICE (JUpiter ICy moons Explorer), which will send a probe to Jupiter and its moons and arrive by 2030s. ESA is also set to launch the Solar Orbiter satellite, which will launch in 2018 to explore the Sun in unprecedented detail.

The 12-year Rosetta mission ended on Sept. 30 when the spacecraft was deliberately crashed on the surface of comet 67P.