On July 1, 2025, the ATLAS telescope in Chile discovered 3I/ATLAS, the third known interstellar comet to enter our solar system and the largest and brightest yet.

NASA’s SPHEREx space observatory detected abundant carbon dioxide in its coma and water ice in its nucleus, showing the comet behaves like a typical solar system comet despite originating elsewhere.

The absence of carbon monoxide suggests 3I/ATLAS was “well baked” before ejection from its parent system and may be two to three times older than solar system comets, Space.com has reported.

SPHEREx’s infrared mapping capabilities allow unprecedented study of such interstellar visitors, and scientists will continue monitoring 3I/ATLAS as it nears the sun in late October, when its water and dust comas are expected to intensify.