A fascinating discovery has unveiled that a small frozen world in the outer solar system possesses an atmosphere, marking it as the second celestial body after Pluto—preceding Neptune—to exhibit such a feature.

This groundbreaking finding, detailed in Natural Astronomy, suggests that these mini-worlds might be more geologically active than previously assumed by planetary scientists.

The celestial body, designated as 2002 XV93, is classified as both an asteroid and a Trans-Neptunian Object (TNO). It orbits the Sun in the Kuiper Belt, a region beyond Neptune’s orbit.

Miniature Pluto: 2002 XV93

2002 XV93’s atmosphere, remarkably thin—about 5 to 10 million times lighter than Earth’s—renders it imperceptible to touch when standing on its surface.

Notably, Pluto is currently the only other TNO known to host an atmosphere, with a diameter of 2,377 km (1,480 miles), which is over five times greater than that of 2002 XV93.

The small size of 2002 XV93 translates to significantly weak gravity, allowing its surrounding atmosphere to easily escape into space. Research indicates this atmosphere could vanish completely within 100 to 1,000 years, implying a continual replenishment of gases.

Two primary theories are posited regarding this atmospheric replenishment:

The first involves frigid volcanic activity. Here, extremely low temperatures cause “volatile substances”—liquids or gases at room temperature, like water, methane, and ammonia—to mimic the behavior of rock or magma.

Ko Arimatsu from the National Astronomical Observatory of Japan, leading the study, stated, “Volatile substances may leak out from beneath the ice surface, possibly due to activities such as polar volcanoes.” These gases can contribute to the formation of an atmosphere.

However, periodic polar volcanic activity has only been observed on larger celestial bodies until now.

The second possibility involves recent external influences. “A small icy object may have recently collided with 2002 XV93, releasing gas or exposing volatile materials,” Arimatsu explained.

“Such collisions are likely rare; thus, the chance of observing a transient atmosphere at the opportune moment is low, yet we cannot dismiss the collision theory.”

In essence, while it seems unlikely that the researchers timed their observations precisely, this angle remains an area of intrigue.

Observation During Solar Eclipse

The orbit of 2002 XV93 around the Sun takes approximately 247 years. Its distant position relative to Earth complicates direct observations.

Arimatsu’s team employed a technique called “occultation,” where a planetary body obscures a distant star as it passes in front.

“If a celestial body had no atmosphere, the starlight would vanish and then reappear distinctly,” says Arimatsu. “However, with an atmosphere present, the gases slightly bend the light, softening the transition.”

On January 10, 2024, three Japanese observatories successfully observed the occultation of 2002 XV93.

“Our findings, particularly from Japan’s Kiso Observatory, demonstrate that the star’s light fades gradually at the edge of the shadow, a phenomenon best explained by the bending of light by a very thin atmosphere surrounding 2002 XV93,” Arimatsu commented.

The research team plans to utilize the James Webb Space Telescope for further analysis of the atmosphere’s composition, but more occultation observations are crucial for definitive answers.

“These observations can reveal whether the atmosphere is dissipating, stable, or evolving over time,” notes Arimatsu.

The gradual decline of the atmosphere points towards it slowly escaping without replenishment, lending credence to the impact theory. In contrast, a more stable or fluctuating atmosphere could indicate a constant supply of gases stemming from the interior of 2002 XV93.

However, occultation requires precise alignments, and, according to Arimatsu, “Only about 10 observatories had the requisite geometry and data quality to investigate the very thin atmosphere surrounding an object of this scale.”

This reality may imply that it will take longer to ascertain the true nature of 2002 XV93’s atmosphere.

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