Interstellar comet 3I/Atlas is unusually enriched with windshield wiper fluid

Comet 3I/Atlas as seen by Hubble
in November 2025. Click for original.
While interstellar comet 3I/Atlas is remarkably like most comets from our own solar system, scientists have now found new evidence that it spalled off unusual amounts of methanol (CH3OH) — material normally used as windshield washer fluid, carburetor fluid, and cooking fuel — when it made its close fly-by of the Sun in the fall of 2025.
You can read the paper here [pdf] . The research also detected large amounts of prussic acid (HCN). As the comet made its closest pass to the Sun, the numbers increased. From the paper’s abstract:
The CH3OH production rate increased sharply from August through October, including an uptick near the inner edge of the H2 O sublimation zone at r H = 2 au. Compared to comets measured to date at radio wavelengths, the derived CH3 OH/HCN ratios in 3I/ATLAS of 124+30 −34 and 79−14 +11 on September 12 and 15, respectively, are among the most enriched values measured in any comet, surpassed only by anomalous solar system comet C/2016 R2 (PanSTARRS).
Though the numbers are high, they aren’t outside the range of what has been found in comets from our own solar system. Instead, this data suggests — as has all data so far — that Comet 3I/Atlas is a normal comet, but unique in its own way, as are all comets and in fact every object in space.

Comet 3I/Atlas as seen by Hubble
in November 2025. Click for original.
While interstellar comet 3I/Atlas is remarkably like most comets from our own solar system, scientists have now found new evidence that it spalled off unusual amounts of methanol (CH3OH) — material normally used as windshield washer fluid, carburetor fluid, and cooking fuel — when it made its close fly-by of the Sun in the fall of 2025.
You can read the paper here [pdf] . The research also detected large amounts of prussic acid (HCN). As the comet made its closest pass to the Sun, the numbers increased. From the paper’s abstract:
The CH3OH production rate increased sharply from August through October, including an uptick near the inner edge of the H2 O sublimation zone at r H = 2 au. Compared to comets measured to date at radio wavelengths, the derived CH3 OH/HCN ratios in 3I/ATLAS of 124+30 −34 and 79−14 +11 on September 12 and 15, respectively, are among the most enriched values measured in any comet, surpassed only by anomalous solar system comet C/2016 R2 (PanSTARRS).
Though the numbers are high, they aren’t outside the range of what has been found in comets from our own solar system. Instead, this data suggests — as has all data so far — that Comet 3I/Atlas is a normal comet, but unique in its own way, as are all comets and in fact every object in space.















