A tiny world at the edge of our solar system grew a mysterious atmosphere, and we don't know how

Key Points:

• A small trans-Neptunian object (612533) 2002 XV93, located in the Kuiper Belt and much smaller than Pluto, has been found to possess a thin atmosphere, a surprising discovery for such a distant and icy body.
• The atmosphere, detected through stellar occultation observations by Japanese astronomers in January 2024, is extremely thin with surface pressures between 100 and 200 nanobars, millions of times less than Earth's atmosphere.
• Scientists are uncertain about the atmosphere's origin since typical ices that sublimate into gases on Pluto are absent on (612533) 2002 XV93; possible explanations include a recent comet impact or cryovolcanic activity releasing subsurface gases.
• This discovery challenges previous assumptions that only larger bodies can maintain atmospheres, suggesting smaller objects in the outer solar system may also support exospheres.
• Future observations, particularly with the James Webb Space Telescope, aim to determine the atmosphere's composition and monitor its density to distinguish whether it is transient from an impact or sustained by ongoing outgassing.