The two proposals were selected from a group of 12 submitted to the New Frontiers program, which supports mid-level planetary science missions. First is the Enceladus Life Finder, which would look for markers of biological activity in the geyser plumes shooting out of Saturn's moon, and second is the Venus In situ Composition Investigations, which would be the first NASA spacecraft to conduct the in-depth exploration of Venus in nearly 30 years.
CAESAR would also do something unprecedented, Squyres said, by not just sampling a comet, but capturing both dust and volatile ices from its interior.
"As everybody knows, comets are among the most scientifically important objects and they are the most poorly understood", said Steve Squyres of Cornell University, who will lead the mission should it be chosen. The mission would be managed by the Applied Physics Laboratory (APL) of Johns Hopkins University, which would also build the spacecraft. "Comets were a source of water for the Earth's oceans, and critically they were a source of organic molecules that contributed to the origin of life".
"We could take a lander, put it on Titan, take these four measurements at one place, and significantly increase our understanding of Titan and similar moons", said Dragonfly project manager Peter Bedini of APL.
The CAESAR (Comet Astrobiology Exploration SAmple Return) mission would acquire a sample from the nucleus of comet Churyumov-Gerasimenko and return it to Earth. Once there, it would collect samples from the comet's nucleus, or core, and then return them to Earth in 2034. That return capsule will be provided by the Japanese space agency JAXA, based on its experience with the Hayabusa asteroid sample return missions. "NASA intends to select one of these studies in the spring of 2019 to continue to subsequent mission phases", the U.S. space agency stated on Wednesday.
The mission would return to Earth on November 20, 2038, unprecedented samples in tow. NASA said in a release.
NASA's Cassini spacecraft studied Titan extensively in a 13-year mission that ended in September, while ESA's Huygens probe landed on Titan's surface in early 2005. For ELSAH, more work is needed to avoid contamination so the mission can better detect potential life on Saturn's icy moon. VICI will improve an element and mineralogy camera to operate in Venus' harsh environment.
The selected mission will be the fourth in NASA's New Frontiers program, a series of principal investigator-led planetary science investigations that fall under a development cost cap of approximately $850 million. "These are tremendously exciting missions".
"This is a giant leap forward in developing our next bold mission of science discovery", Thomas Zurbuchen, associate administrator for NASA's Science Mission Directorate in Washington, said in a statement.
These missions aren't meant to be the really big stuff - nobody will be heading off to Proxima-b in the neighboring galaxy - but rather mid-sized projects that would be impossible for most scientists around the world, but which NASA can handle more easily.