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]
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
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 Saturn 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.[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] The landing is envisioned to take place in 2052.[3]
Project history
ESA Director General Josef Aschbacher giving a short presentation on the agency's proposed L4 mission during the ministerial council in 2025
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]
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