NASA’s SPHEREx Detects Organic Molecules In Interstellar Comet

NASA’s SPHEREx space telescope has delivered new insights into interstellar comet 3I/ATLAS, only the third such object ever observed passing through the solar system. Observations made in December 2025 revealed a rich mix of organic molecules and heightened cometary activity, strengthening scientific understanding of material formed beyond the Sun’s influence.

Infrared observations of a rare interstellar visitor

The NASA’s SPHEREx mission turned its infrared instruments toward comet 3I/ATLAS shortly after it passed closest to the Sun. Scientists detected organic molecules including methanol, cyanide and methane. While these compounds are central to biological processes on Earth, researchers emphasise that such molecules can also form through non-biological processes in space.

Post-perihelion brightening and cometary activity

Mission scientists reported a dramatic increase in the comet’s brightness nearly two months after its closest approach to the Sun. This delayed surge is linked to sublimation, a process in which frozen ices turn directly into gas as heat penetrates deeper layers of the comet. Escaping gases form a surrounding atmosphere, or coma, rich in water vapour, carbon dioxide and carbon monoxide.

Evidence of pristine subsurface material

According to the research team, the delayed venting suggests that deep, previously unexposed ices began erupting well after peak solar heating. Observations indicate that 3I/ATLAS released carbon-rich material that had remained locked beneath its surface for billions of years. Scientists also noted the presence of soot, rocky dust and large solid fragments, indicating that the comet is ejecting heavier material than typically seen.

Important Facts for Exams

• SPHEREx studies the universe in 102 infrared wavelengths.
• Interstellar comets originate outside the solar system.
• Sublimation is the direct transition of ice to gas.
• Organic molecules can form through abiotic processes in space.

Mission capability and discovery background

SPHEREx, managed by NASA Jet Propulsion Laboratory, was launched in March 2025 to map the cosmos and search for ingredients of life. Its all-sky infrared surveys enabled timely detection of the comet’s evolving chemistry. Comet 3I/ATLAS was first identified in July 2025 by the ATLAS telescope in Chile and confirmed as interstellar due to its extreme velocity and trajectory. Scientists say the findings highlight how space telescopes can capture rare opportunities to study material from distant star systems passing briefly through our solar neighbourhood.