By Will Dunham WASHINGTON, May 4 (Reuters) - In the far reaches of our solar system - beyond the outermost planet Neptune - resides a host of icy and desolate celestial bodies. Among these objects, only the dwarf planet Pluto was known to possess an atmosphere - until now.

Pluto was believed to be the only body beyond Neptune with an atmosphere. Now, a new discovery in our solar system is challenging that assumption.

A comet born around another star is carrying water unlike anything ever measured in our solar system. Interstellar comet 3I/ATLAS, first detected by the ATLAS survey on July 1, 2025, contains water so heavily laced with deuterium that the ratio exceeds anything recorded from a solar system object by a factor of more than 40.

Scientists are grappling with a cosmic mystery: why does the Universe behave differently on massive scales compared to our own solar system? While distant galaxies reveal clear signs of something bending the rules of gravity—often attributed to dark energy or a hidden “fifth force”—everything nearby seems to follow Einstein’s playbook perfectly.

An interstellar comet carries water unlike anything in our solar system, revealing a far colder birthplace and clues about planetary systems

Learn more about the interstellar traveler, Comet 3I/ATLAS, and what researchers know about its place of origin.

A new solar telescope at Paranal studies the Sun to reduce stellar noise, helping scientists better detect and study Earth-like exoplanets around distant stars.

A comet from another star system is carrying water unlike anything astronomers have ever measured in our cosmic neighborhood. Observations published in June 2026 in Nature Astronomy reveal that interstellar comet 3I/ATLAS contains more than 40 times the concentration of deuterium,