Uranus and Neptune, the outermost ice giants, remain largely unexplored worlds between the gas giants and the terrestrial planets. Their small apparent size and great distance have made them difficult to study, with only the Voyager 2 flybys in 1986 and 1989 providing close-up data. Most of what we know about their atmospheres comes from observations from Earth and space telescopes, which cannot directly measure key properties such as composition, thermal structure, clouds and dynamics. The lack of in situ data limits our understanding of their properties and their role in the formation and evolution of the Solar System.

In this context, the scientific community continues to promote collaboration on the Uranus Orbiter and Probe (UOP) mission with an emphasis on the value of international participation in science and technology. This effort was exemplified by the workshop on In Situ Exploration of the Giant Planets II, held from 12 to 14 July 2022 at the Johns Hopkins University Applied Physics Laboratory in Laurel, MD, USA. This event followed the inaugural workshop, which took place in 2019 in Marseille, France and resulted in the Space Science Reviews collection "In Situ Exploration of the Ice Giants: Science and Technology". Bringing together approximately 100 participants, the 2022 Laurel workshop focused on all giant planets, aiming to strategize the way forward for future entry probe missions.

This new topical collection contains a series of papers based on the presentations and discussions at the 2022 Laurel workshop, providing a timely and comprehensive overview of the current state of science, instrumentation, and mission concepts related to the exploration of icy giant atmospheres with entry probes. Covering key scientific questions, methods to address them, and associated technological challenges, this collection serves as an essential reference for graduate students and researchers working in the field of giant planet exploration and related scientific investigations.

Please, start reading the editors' introduction: Mandt, K.E., Atkinson, D.H. & Mousis, O. Editorial to the Topical Collection: In Situ Exploration of the Giant Planets II. Space Sci Rev 221, 5 (2025). https://doi.org/10.1007/s11214-024-01131-9