Tiny Frozen World Surprisingly Found to Have an Atmosphere

Artist’s impression of the trans-Neptunian object (612533) 2002 XV93 blocking the light from a distant star

NAOJ/Ko Arimatsu

Astronomers have discovered that a tiny icy object at the edge of the solar system unexpectedly has a thin atmosphere.

The object, (612533) 2002 XV93, is located in the Kuiper Belt and is less than 500 kilometers in diameter. It belongs to a group of objects that share a similar orbit with Pluto.

In January 2024, scientists observed the object passing in front of a distant star. Instead of the starlight disappearing instantly, it gradually faded and returned, suggesting the presence of an extremely thin atmosphere around the object.

Researchers estimate the atmospheric pressure is millions of times thinner than Earth’s atmosphere, and even much thinner than Pluto’s. Although humans could not breathe in it or see a sky like Earth’s, the atmosphere is still thick enough to bend starlight.

Scientists believe the atmosphere may contain methane, nitrogen, or carbon monoxide, but its origin remains unclear. Possible explanations include internal gas release, icy volcanic activity, or even past collisions.

This discovery challenges previous ideas about small bodies in the outer solar system, since objects as small as 2002 XV93 were not expected to be able to maintain an atmosphere.