Interstellar Comet Reveals Unique Composition Never Seen Before

WHO:

Phys.org - Astronomers are studying the interstellar comet 3I/Atlas.

The Conversation - A trio of studies has been published regarding the comet.

WHAT:

Phys.org - The composition of 3I/Atlas is strikingly different from any object found in our solar system.

The Conversation - 3I/Atlas is an interstellar object (ISO), the third such object found after 1I/ʻOumuamua and 2I/Borisov.

The Conversation - 3I/Atlas contains a unique chemical cocktail including water, carbon dioxide, carbon monoxide, methane, cyanides, sulphides, and free-floating iron and nickel atoms.

The Conversation - The D/H ratio of 3I/Atlas's water is around 1%, significantly higher than all observed solar system comets.

The Conversation - The ¹²C/¹³C ratio of 3I/Atlas is far above all solar system values.

WHERE:

The Conversation - 3I/Atlas was discovered traveling through the inner solar system.

WHEN:

The Conversation - 3I/Atlas is believed to have been born around 12 billion years ago.

The Conversation - 3I/Atlas was discovered almost exactly one year ago.

WHY:

The Conversation - The unique composition of 3I/Atlas provides insights into the conditions of the protoplanetary disk in which it formed.

HOW:

The Conversation - The chemical composition of 3I/Atlas was determined using spectroscopy, which splits light into its constituent wavelengths.

The Conversation - The studies utilized data from the James Webb Space Telescope to measure the spectral signatures of water and carbon dioxide.

(UPDATED July 3, 2026 08:05 UTC)

Astronomers are currently studying the interstellar comet 3I/Atlas, which has a composition strikingly different from any object found in our solar system. This unique comet, discovered traveling through the inner solar system almost exactly one year ago, contains a fascinating chemical cocktail, including water, carbon dioxide, and free-floating iron and nickel atoms, with a D/H ratio of its water around 1%, significantly higher than all observed solar system comets. Researchers utilized data from the James Webb Space Telescope to analyze its spectral signatures, providing valuable insights into the conditions of the protoplanetary disk where 3I/Atlas was born approximately 12 billion years ago.