NASA has selected two finalist concepts for a robotic mission planned to launch in the mid-2020s: a comet sample return mission and a drone-like rotorcraft that would explore potential landing sites on Saturn’s largest moon, Titan.

The agency announced the concepts Wednesday, following an extensive and competitive peer review process. The concepts were chosen from 12 proposals submitted in April under a New Frontiers program announcement of opportunity.

“This is a giant leap forward in developing our next bold mission of science discovery,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate in Washington. “These are tantalizing investigations that seek to answer some of the biggest questions in our solar system today.”

The finalists are:

Comet Astrobiology Exploration Sample Return (CAESAR)

The CAESAR mission seeks to return a sample from 67P/Churyumov-Gerasimenko, a comet that was successfully explored by the European Space Agency’s Rosetta spacecraft, to determine its origin and history. Led by Steve Squyres of Cornell University in Ithaca, New York, CAESAR would be managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Dragonfly

Dragonfly is a drone-like rotorcraft that would explore the prebiotic chemistry and habitability of dozens of sites on Saturn’s moon Titan, an ocean world in our solar system. Elizabeth Turtle from the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, is the lead investigator, with APL providing project management.

The CAESAR and Dragonfly missions will receive funding through the end of 2018 to further develop and mature their concepts. NASA plans to select one of these investigations in the spring of 2019 to continue on to subsequent mission phases.