Interstellar Comet 3I/ATLAS Carries The Key Molecules For Life In Unusual Abundance– What Does That Mean?

Our third interstellar visitor that we have detected, comet 3I/ATLAS, has been found to contain molecules that are key for life. But what does that mean? 

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If you don't know the story by now, on July 1, 2025, the Asteroid Terrestrial-impact Last Alert System did its job beautifully and spotted an object as it hurtled its way through our Solar System. The object, now known to be a comet due to its distinct cometary behavior, was soon confirmed to be interstellar, and likely older than the Solar System it is temporarily passing through.

It has traveled alone, possibly for billions of years, and now as it heads through our neck of the cosmos astronomers on Earth and using humanity's space-based telescopes have had an opportunity to study it – a traveler from a different part of the galaxy, and an earlier age in the universe. But while December 19 brought the object's closest approach to Earth, we won't have too long before it heads out of the Solar System and away from our gawping telescopes.

“That’s the great joy of interstellar objects, they’re giving us clues, because they’re made up of the building blocks of planet formation elsewhere in the galaxy. They’re telling us about a star that’s so ancient it might not even exist anymore," Associate Professor Michele Bannister, from the School of Physical and Chemical Sciences at Te Whare Wānanga o Waitaha | University of Canterbury (UC), and key member of a team studying the object, explained in a statement.

"This comet is a calling card from the past, and we only have a few hundred days to try and interpret what it’s telling us.”  

In our short time viewing the object, scientists have found some interesting things and unusual chemistry. Of particular interest is that it contains molecules that are key to life, and in abundance compared to most Solar System comets.

"We report the detection of methanol (CH₃OH) toward interstellar comet 3I/ATLAS using the Atacama Compact Array of the Atacama Large Millimeter/Submillimeter Array (ALMA) on UT 2025 August 28, September 18 and 22, and October 1, and of hydrogen cyanide (HCN) on September 12 and 15," a recent preprint paper explains.

"The CH₃OH production rate increased sharply from August through October, including an uptick near the inner edge of the H₂O sublimation zone at r H = 2 au. Compared to comets measured to date at radio wavelengths, the derived CH₃OH/HCN ratios in 3I/ATLAS of 124⁺³⁰ ₋₃₄ and 79⁺¹¹₋₁₄ 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)."

To be clear, these molecules are not themselves indication of life on the comet. We've had enough of the (unnecessary and outlandish) hypothesis that 3I/ATLAS is an alien spacecraft, we don't want people thinking that the comet contains life either. But they are considered so-called "building blocks" of life.

"Life as we know it requires building blocks, such as amino acids," NASA explains, "and hydrogen cyanide is one of the most important and versatile molecules needed to form amino acids." 

Similarly, methanol can be used to form more complex molecules like sugars, amino acids, and DNA/RNA precursors. In 3I/ATLAS, methanol is unusually abundant, making up around 8 percent of the comet's vapor, compared to around 2 percent in solar system comets. 

“It seems really chemically implausible that you could go on a path to very high chemical complexity without producing methanol,” Martin Cordiner, of NASA’s Goddard Space Flight Center in Maryland and author on the paper, explained to New Scientist.

While seeing these building blocks doesn't mean that there are complex molecules on 3I/ATLAS, it is still intriguing to see them in our third interstellar visitor. It has long been suggested that asteroids and comets could have seeded early Earth with the essential ingredients for life, such as organic molecules and water. 

These, including evidence for water ice, have all been seen on comet 3I/ATLAS. While many on the Internet, and certain Harvard astronomers, cling onto the "alien spacecraft" hypothesis, the presence of these ingredients necessary for life could be among our first evidence that the building blocks of life are out there in the galaxy. And though we need to wait for more study and evidence, perhaps from a fourth interstellar visitor, that's pretty exciting indeed.

The preprint has been submitted to The Astrophysical Journal Letters and is available via arXiv. 

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