L4 (spacecraft)

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This article is about the ESA spacecraft. For other uses, see L4 (disambiguation).

L4
Mission typeEnceladus orbiter and lander
OperatorESA
Start of mission
Launch dateearly 2040s
RocketAriane 6
← LISA

L4 is a proposed mission to Enceladus by the European Space Agency (ESA). If approved, it is expected to be launched in the early 2040s. Since 2024, Enceladus has been identified as the European Space Agency's top priority for space exploration due to strong signs of potential habitability.[1][2] The mission will consist of an orbiter and a lander.[3][4][5][6]

Science

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Enceladus is an icy ocean-bearing moon of the planet Saturn that is considered to have some of the greatest potential to harbor life within the liquid water ocean beneath its icy crust. It is one of the very few geologically active objects in the Solar System as its underground ocean spews out geysers of water. According to planetary scientists, the water in these plumes is in direct contact with the moon’s rocky interior, which may contain chemicals necessary for life.

Unlike other ocean planets and moons whose underground oceans are buried underneath miles of thick, solid ice, Enceladus's internal ocean can be observed more directly by analyzing the water erupting from its plumes.[7] The possibility of Enceladus's potential habitability was further amplified when the Cassini space probe detected molecules from the moon's watery plumes that life needs to survive such as phosphates and salts.[8]

A false-color photo mosaic of Enceladus. The bluish lines below correspond to the moon's tiger stripes where the moon's underwater geysers erupt from

Mission profile

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The L4 probe is proposed to be launched in the early 2040s aboard two new generation Ariane 6 rockets, arriving at Saturn around a decade later.[9] The ESA chart shows that the spacecraft will be composed of two parts which will need to be assembled while in outer space.

Ideally, L4 should arrive at Saturnian around the time when the planet and its moons' southern poles are illuminated by the Sun—around Saturn's southern summertime—to allow the space probe to study Enceladus's geysers which are located on the moon's south pole.[10]

After arriving at the Saturn system, the probe will then perform multiple flybys of Enceladus and Saturn's other icy moons, including Titan, Rhea, Dione, Tethys, and Mimas, which will help scientists learn more about Enceladus's "sibling" icy moons as well.[11]

After performing multiple sampling of the moon's geysers while in orbit, the L4 spacecraft will then land on Enceladus' south pole where the active geysers are located.[12]

Project history

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ESA Director General Josef Aschbacher giving a short presentation on the agency's proposed L4 mission during the ministerial council in 2025

Between 2018 and 2021, ESA scientists worked on defining priorities for Voyage 2050, a next phase of ESA's Science Programme after Cosmic Vision. They identified three priority themes for the programme's large-scale missions: the Solar System's icy moons (with Enceladus as a prime candidate for an astrobiology-focused mission), exoplanets, and the nature of the early Universe.[13][14] The 2023-2032 Planetary Science Decadal Survey, published by US scientists in 2022, listed a mission to Enceladus as its second priority for the decade.[15][16]

In 2024, ESA identified Enceladus as the most promising target for its next L-class mission to be implemented within the Voyage 2050 programme after JUICE (L1), LISA (L2), and Athena (L3).[14] During the 2025 ministerial council of ESA member states, which committed to the largest ever budget for the agency, Director General Josef Aschbacher mentioned L4 to Enceladus as one of the agency's top potential future projects.[17][18][19]

See also

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References

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  1. ^ "Saturn's moon Enceladus top target for ESA". ESA. 2024. Retrieved 30 November 2025.
  2. ^ Helbert, Jörn; Bründl, Tara-Maria; Haag, Martin; Lindner, Martin; Ordoubadian, Björn; Wittig, Sven (9 July 2025). The Mission to Enceladus – The ESA L4 mission (Report). Copernicus Meetings. doi:10.5194/epsc-dps2025-1307.
  3. ^ Pao, Jeff. "ESA Seeks Budget Hike to Secure Enceladus Mission Under Voyage 2050". www.techjournal.uk. Retrieved 30 November 2025.
  4. ^ "ESA Outlines Saturn Mission With Enceladus Landing | Aviation Week Network". aviationweek.com. Retrieved 30 November 2025.
  5. ^ Andrew Jones (27 September 2025). "Europe wants to launch a life-hunting mission to Saturn's icy ocean moon Enceladus". Space. Retrieved 30 November 2025.
  6. ^ "We're Going To Enceladus (Maybe)! ESA's Plans For Alien-Hunting Mission To Land On Saturn's Moon Is A Go". IFLScience. 28 November 2025. Retrieved 30 November 2025.
  7. ^ "Enceladus". NASA. 2025. Retrieved 30 November 2025.
  8. ^ Postberg, Frank; Sekine, Yasuhito; Klenner, Fabian; Glein, Christopher; Zou, Zenghui; Abel, Bernd; Furuya, Kento; Hillier, Jon; Khawaja, Nozair; Kempf, Sascha; Noelle, Lenz; Saito, Takuya; Schmidt, Juergen; Shibuya, Takazo; Srama, Ralf (14 June 2023). "Detection of phosphates originating from Enceladus's ocean". Nature. 618 (7965): 489–493. Bibcode:2023Natur.618..489P. doi:10.1038/s41586-023-05987-9. PMC 10266972. PMID 37316718. S2CID 259157087.
  9. ^ "Saturn's moon Enceladus top target for ESA". ESA. 2024. Retrieved 30 November 2025.
  10. ^ "ESA Member States commit to largest contributions at Ministerial". ESA. 2025. Retrieved 30 November 2025.
  11. ^ "Report of the Expert Committee for the Large-class mission in ESA's Voyage 2050 plan covering the science theme "Moons of the Giant Planets"" (PDF). ESA. 2024. Retrieved 30 November 2025.
  12. ^ "Saturn's moon Enceladus". www.esa.int. Retrieved 30 November 2025.
  13. ^ "Voyage 2050 Final recommendations from the Voyage 2050 Senior Committee". ESA. 2021. Retrieved 30 November 2025.
  14. ^ a b Parsonson, Andrew (2 April 2024). "Saturn's Moon Enceladus Identified as Primary Target for ESA". European Spaceflight. Retrieved 30 November 2025.
  15. ^ "Report Identifies Priority Planetary Science Missions, Planetary Defense Efforts, and Strategic Investments for the Next Decade". www.nationalacademies.org. Retrieved 30 November 2025.
  16. ^ "Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023-2032". National Academies. 2022. Retrieved 30 November 2025.
  17. ^ "ESA Council meeting at Ministerial level 2025 - press conference". ESA. 2025. Retrieved 30 November 2025.
  18. ^ "How the European Space Agency plans to catch up in space race". euronews. 27 November 2025. Retrieved 30 November 2025.
  19. ^ "ESA Member States commit to largest contributions at Ministerial". ESA. 2025. Retrieved 30 November 2025.