WASHINGTON — NASA signed an agreement in September with a foundation to support initial studies of a privately funded mission to a potentially habitable moon of Saturn.

The unfunded Space Act Agreement between NASA and the Breakthrough Prize Foundation, initiated with little public fanfare, covers NASA support for initial concept studies, known in NASA programmatic parlance as “Pre-Phase A,” for a mission to the moon Enceladus, an icy world believed to have a subsurface ocean of liquid water and plumes that eject that water through the surface into space.

The agreement, the seven-page document posted on a NASA website states, “shall be for the purpose of cooperating on the Breakthrough Pre-Phase A activities for Breakthrough’s Enceladus Mission.” That includes supporting a series of reviews that leads up to what NASA calls Key Decision Point (KDP) A, “to determine progress to Phase A, for further formulation of the Enceladus Mission’s concept and technology development.”

The agreement includes a series of milestones from March through December 2019, such as development of preliminary project requirements in June and a mission concept review in September. The final milestone, in December 2019, would be KDP-A, where “NASA and Breakthrough provide recommendation on whether project should proceed to Phase A.”

Most of the study work would be done by Breakthrough. NASA, under the agreement, would use “reasonable efforts” to offer scientific and technical consulting for the study, including expertise in a range of scientific fields and in planetary protection. NASA will also advise “in the development of Phase A plans for a life signature mission to Enceladus.”

The agreement between NASA and Breakthrough involves no exchange of funds. NASA estimates its cost of carrying out its responsibilities under the agreement to be $72,384.

The agreement, first reported by New Scientist, offers few details about the proposed mission itself. A companion document for the agreement notes that the foundation’s Breakthrough Watch program “seeks to evaluate near-term missions to objects in the Solar System, including Enceladus,” that would search for signs of life there. “The Enceladus Mission is considering novel low-cost approaches, one of which uses solar sail technology to flyby the moon of Saturn to collect scientific data.”

However, foundation officials have publicly discussed their interest in an Enceladus mission for a year. “We formed a little workshop around this idea,” said Yuri Milner, the Russian billionaire who funds the foundation, at an event in Seattle in November 2017. “Can we design a low-cost privately-funded mission to Enceladus, which can be launched relatively soon and that can look more thoroughly at those plumes to try to see what’s going on there?”

Pete Worden, the former director of NASA’s Ames Research Center who is chairman of the Breakthrough Prize Foundation, mentioned at the NewSpace Europe 2017 conference in Luxembourg last November that the organization was considering some non-traditional concepts for an Enceladus mission, including using solar sails.

“We’ll probably kick off, around the first of the year, a six-month study to look at some of these” alternative mission concepts, he said then, leaving the door open to cooperation with NASA or other space agencies. “Hopefully, later this next year, if it looks good, we’ll be off and running.”

During a panel discussion at a space conference at Arizona State University Aug. 20, Worden indicated an agreement with NASA was in place to study an Enceladus mission. “This week we signed an agreement with NASA to look at a privately funded mission that will work with NASA that will go to the outer solar system and look for life either on Enceladus or Europa,” he said. “We think we can do those missions for tens of millions, not hundreds of millions or billions.”

A Breakthrough Prize Foundation spokesperson, contacted by SpaceNews the day of those comments, said the agreement had not yet been finalized. A NASA spokesperson did not comment on the agreement then.

The Space Act Agreement was, in fact, signed Sept. 13, according to the documents posted online. Worden signed the document on behalf of the Breakthrough Prize Foundation and Thomas Zurbuchen, NASA associate administrator for science, signed for NASA.

Even after the agreement was signed, though, neither NASA nor Breakthrough were willing to talk about it. Interviewed during an event at the International Astronautical Congress in Bremen, Germany, Oct. 2 about a separate Search for Extraterrestrial Intelligence initiative by Breakthrough in South Africa, Worden said the foundation was not yet ready to make an official announcement about the study.

A Breakthrough spokesperson, contacted by SpaceNews Nov. 8, promised to “circle back” about the agreement, but did not follow up. A NASA spokesperson also did not respond to a Nov. 8 request for comment about the agreement.