TheOcean Worlds Exploration Program (OWEP) is aNASA program[1] to exploreocean worlds in theouter Solar System that could possesssubsurface oceans to assess theirhabitability and to seekbiosignatures of simpleextraterrestrial life.
Prime targets includemoons that harbor hidden oceans beneath a shell of ice:Europa,Enceladus, andTitan. A host of other bodies in the outer Solar System are inferred by a single type of observation or by theoretical modeling to have subsurface oceans.
The US House Appropriations Committee approved the bill on May 20, 2015, and directed NASA to create the Ocean Worlds Exploration Program.[2] The "Roadmaps to Ocean Worlds" (ROW) was started in 2016,[3][4] and was presented in January 2019.[5] The formal program is being implemented within the agency by supporting theEuropa Clipper orbiter mission to Europa,[3][6] and theDragonfly mission to Titan. The program is also supporting concept studies for a proposedEuropa Lander,[7] and concepts to explore the moonTriton.[8][5]Amanda Hendrix and Terry A. Hurford are the co-leads of the NASA Roadmaps to Oceans World Group.[5][9]
The chief author of NASA's budget proposal isJohn Culberson, who was at the time the head of the science subcommittee in theHouse of Representatives. In Spring 2015 he presented a budget request, creating the possibility of an all-new NASA mission program.[11][12] The House Appropriations Committee approved its version of the FY2016 House Appropriations Commerce-Justice-Science (CJS) bill on May 20, 2015.[6] Therefore, the Committee directed NASA to create the Ocean Worlds Exploration Program whose primary goal is to discover extant life on another world using a mix ofDiscovery,New Frontiers andFlagship class missions consistent with the recommendations of current and futurePlanetary Science Decadal Surveys.[3]
In the FY2017 Budget Request, the committee recommended $348 million for "Outer Planets" and "Ocean Worlds," of which not less than $260 million is for theEuropa Clipper orbiter and lander, with launch of the orbiter in 2025[13] and the potentialEuropa Lander shortly after.[14]
A 2017 technical analysis stated that the technical challenges are enormous, and that "Without a genuinely strategic program plan, the great promise of an OWEP [Ocean Worlds Exploration Program] is highly likely to remain unfulfilled."[15] The report noted that development of OWEP-enabling technologies must currently compete for priority with other Solar System objectives, which is not useful for strategic planning. The report recommends common, multi-mission technical infrastructure and secure funding to develop it.[15]
The Roadmaps to Ocean Worlds (ROW) report was submitted and it was published in January 2019.[5]
OnEarth, itself an ocean world, liquid water is essential tolife as we know it. A question is whether the dark, alien oceans of the outer Solar System could be habitable for simple life forms, and if so, what theirbiochemistry might be.[16]
The goals of the Ocean Worlds Exploration Program are to "identify ocean worlds, characterize their oceans, evaluate their habitability, search for life, and ultimately understand any life we find."[5]
Exploring these moons could help to answer the question ofhow life arose on Earth and whether it exists anywhere else in the Solar System.[17] It may also be possible to find pre-biotic chemistry occurring, which could provide clues to how life started on Earth.[18] Any life detected at the remote ocean worlds in theouter Solar System would likely have formed and evolved along an independent path from life on Earth, giving us a deeper understanding of the potential for life in theuniverse.[4]
Oceanographers,biologists andastrobiologists are part of the team developing the strategy roadmap.[3] The planning also considers implementingplanetary protection measures to avoid contaminating extraterrestrial habitable environments with resilient stowaway bacteria on their landers.[3][4]
Ocean worlds identified in the Solar System so far with reasonable certainty are themajor moonsEuropa,Enceladus,Titan,Ganymede, andCallisto.[5] Of these, Europa and Enceladus have the highest priority because their icy shells are thinner than the others (Enceladus’ is less than 10 km; Europa's is about 40 km) and there is some evidence their oceans are in contact with the rockymantle, which could provide both energy and chemicals for life to form.[5] Enceladus' ice crust hasfractures at the south pole that allow ice and gas from the ocean to escape to space, where it has been sampled bymass spectrometers aboard theCassini Saturn orbiter with tantalizing results.[19] Titan's ocean is the deepest, at 50 to 100 km, and no evidence for active plumes or ice volcanism have been observed.
Bodies such asTriton,Pluto,Ceres,Miranda,Ariel, andDione are considered candidate ocean worlds, based on hints from limited spacecraft observations.[5]
The Ocean Worlds Exploration Program (OWEP) is supporting theEuropa Clipper orbiter mission to Europa, which is the first planned target of this program to be launched in 2024.[3][6] The second is theDragonfly mission to Titan.[5]
The program is also supporting concept studies for a proposedEuropa Lander,[7] and a concept to explore the moon Triton withTrident, a mission selected as a finalist in NASA'sDiscovery Program in 2020.[8][5]
Astrobiology mission concepts to water worlds in the outer Solar System:
In fact, the report accompanying the bill directs NASA to create an "Ocean Worlds Exploration Program" of which the Europa mission is part.
