"I am very much in the camp of 'make Pluto a planet again,'" NASA Administrator Jared Isaacman stated during a Senate hearing on Tuesday, signaling his support for reopening the scientific debate on Pluto's classification.
Current Classification and Reclassification History
Discovered in 1930 by Clyde Tombaugh, Pluto was considered the ninth planet in the solar system for 76 years. In 2006, the International Astronomical Union (IAU) reclassified Pluto as a dwarf planet.
The IAU's definition requires a planet to:
- Orbit the Sun
- Have sufficient mass for self-gravity to achieve a round shape
- Have "cleared its orbital neighborhood" of other debris
Pluto does not meet the third criterion. The discovery of other similarly sized bodies, such as Eris in 2004, preceded the IAU's decision to clarify the definition of a planet. Pluto is approximately 1,400 miles wide and resides in the Kuiper Belt beyond Neptune.
Administrator's Stance and Agency Actions
Isaacman stated that he believes Pluto should not have been reclassified and that NASA researchers are working on studies that could be proposed to the scientific community to revise the classification. Isaacman, who was confirmed as NASA Administrator in December 2025, has previously expressed similar views in media interviews.
Scientific Community Reactions
The proposal has drawn a range of responses from scientists:
- Planetary scientist Amanda Hendrix stated that the debate distracts from more significant scientific issues.
- Astrobiologist David Grinspoon, who opposed Pluto's demotion, supports reopening the discussion but cautioned that the IAU holds authority over such classification decisions, not NASA.
- Planetary scientist Adeene Denton criticized the timing of Isaacman's statement, noting it follows his endorsement of a proposal to reduce NASA's science budget.
Path to Reclassification
Any official reclassification of Pluto would require the IAU to revise its definition of a planet. The debate involves scientists who, based on Pluto's geology and atmosphere, argue it should be considered a planet, while others maintain the current definition.