These remote, largely unexplored planets contain clues to the solar system's origins, according to Yang Mengfei, chief designer of the Chang'e 5 mission and senior researcher at the China Academy of Space Technology. "Ice giants preserve pristine gaseous materials that record the evolutionary history of protostellar clouds and crucial information about planetary formation," Yang told China Daily.
Composed mostly of elements heavier than hydrogen and helium, such as oxygen, carbon, and nitrogen, Uranus and Neptune are classified as ice giants. Uranus, which has the coldest atmosphere in the solar system at about minus 224 C, also rotates with the most extreme axial tilt. Neptune, the solar system's outermost planet, boasts winds reaching up to 2,100 km/h.
Neptune's moon Triton stands out as a potential hotspot for extraterrestrial life. Believed to have been captured from the Kuiper Belt, Triton orbits opposite to Neptune's rotation-a rare trait among large moons. Its potential subsurface ocean makes it a prime candidate for astrobiological studies.
Yang emphasized the urgency of investigating these planets. "The formation and evolution of ice giants represent a cutting-edge frontier in planetary science," he said. "These planets remain among the least explored realms in our solar system."
Due to limited direct observation, current models of Neptune and Uranus' internal structure carry large uncertainties. Yang noted that both the European and U.S. space agencies have prioritized ice giant exploration. With China's advancements in nuclear-powered spacecraft, the country is technically ready to undertake such a mission.
"China should strive to become the first to achieve orbital exploration of an ice giant," Yang stated. To date, only NASA's Voyager 2 has flown by Uranus and Neptune, offering brief glimpses during its 1980s mission.
Wang Chi, director of the National Space Science Center, echoed Yang's sentiment. "A dedicated, integrated mission to explore the ice giants is therefore very necessary, as it holds tremendous scientific value," he said. A mission targeting both Neptune and Triton would offer rich returns on planetary science and astrobiology.
He emphasized Triton's potential in the search for "ocean worlds," as the moon may host a subsurface sea. China's national space science roadmap, issued in October 2024, named habitability and life detection on ice giants as top priorities. According to the plan, feasibility research on an ice giant mission could begin in 2028, spanning roughly eight years.
Yang suggested that China could launch its Neptune orbiter in 2033, shortly after deploying a Jupiter probe. The mission, he explained, would combine atmospheric fly-through and orbital measurements to study Neptune's magnetosphere, atmospheric layers, and internal dynamics. It would also investigate Triton's interaction with solar wind and search for biosignatures beneath its icy crust.
"This will deliver a groundbreaking scientific achievement ... and will help to establish China's reach across the entire solar system, elevate our overall technological prowess in the space industry, and position China at the global forefront of space exploration," Yang said.
To promote the initiative, Yang, Wang, and colleagues published two academic articles in the latest issue of Chinese Space Science and Technology, detailing the scientific rationale, technical hurdles, and mission strategies for an ice giant expedition.
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