The icy moons of the gas giant planets are one of the most promising places for hosting microbial life in the present time in our solar system. Missions such as NASA’s Europa Clipper will be launched in the coming years to establish whether icy moons such as Europa are able to support microbial life.
Once this is established, several other mission concepts currently being investigated would be capable of searching for signs of any microbial life on Enceladus, Europa or other icy moons. One of these concepts involves flying through the water vapor plumes observed on Enceladus that are assumed to blast water and ice particles coming from the subglacial ocean on that moon. These plumes are assumed to be connected directly to the subglacial ocean on Enceladus and could thus carry signatures of any life native to Enceladus. There are strong indications that such plumes exist also on Europa and could also exist on other icy moons.
When will a sample from one of the icy moons in the outer solar system be successfully returned to Earth?
The question resolves on the date that a sample from any of the icy moons in the outer solar system (in the asteroid belt and beyond) is successfully returned to be analyzed in a lab by humans. The resolution date will be the date the sample safely arrives at the lab. If this does not happen before January 1, 2100, this will resolve as ">January 1, 2100".
An "icy moon" is defined here as any natural body in the outer solar system (asteroid belt and beyond) with a current stable body of liquid water, excluding the gas giant planets (Jupiter, Saturn, Uranus, Neptune).
The returned sample can be captured either in the plumes, from the surface, or anywhere else on an icy moon, and must safely reach a lab to be analyzed by humans.
The mission science requirements for the sample return should include astrobiological goals and the returned sample should be of sufficient quantity and quality to satisfy these astrobiological mission requirements.
The lab could be anywhere on Earth or in Earth orbit. If first sampling is performed in-situ by a human spaceflight mission, this question will resolve ambiguously.