In July 2025, a faint glow moving between the stars set off alarm bells for astronomers. It was not just another comet. Its hyperbolic trajectory indicated that it was not orbiting our Sun, but rather came from another star system. The visitor was named 3I/ATLAS, the third interstellar object detected after Oumuamua and Borisov, and Since then it has sparked a mix of scientific curiosity and cosmic speculation.
Today, while NASA and ESA continue their movements with the Hubble and James Webb telescopes, theoretical physicist Avi Loeb once again challenges our certainties: what if this comet It will not only carry the basic ingredients of life, but the traces of a “divergent life”a form of biology different from terrestrial biology?
According to NASA, 3I/ATLAS will approach the Sun up to about 1.4 astronomical units, almost the distance of Mars. Its speed, more than 210,000 kilometers per hour, confirms its interstellar origin. But the most striking thing is his behavior: Unlike comets in the solar system, it began to sublimate (release gases and dust) when it was still almost four astronomical units away.beyond the orbit of Jupiter.
James Webb observations have detected intense emissions of carbon dioxide (CO₂) at 4.3 microns and water (H₂O) at 2.7 microns. Hubble, for its part, has recorded a coma (the envelope of gas and dust that surrounds the nucleus) more than 100,000 kilometers in diameter, with a long luminous tail that grows every week. ESA coordinates an international network of telescopes in Chile, Hawaii and Australia to follow the evolution of its brightness, which behaves like a small shooting star in slow motion.
In chemical terms, 3I/ATLAS appears rich in water and carbon dioxide, with proportions that don’t quite fit with solar comets. That difference is what makes Some scientists consider this object a time capsule of another stara natural sample of what could have formed in distant regions of the galaxy.
Comets, both ours and visitors’, They have been considered carriers of the ingredients of life for decades.. They are known to contain amino acids, alcohols, formaldehyde and simple sugars: organic molecules that, upon reaching young planets, could have seeded prebiotic chemistry.
In 2023, the Rosetta probe already confirmed that comet 67P/Churyumov-Gerasimenko contained glycine, the simplest amino acid. If a local comet can host it, why not an interstellar one? 3I/ATLAS spectral analyzes have not yet detected such complex compoundsbut the presence of water, carbon dioxide and metals outlines a familiar scenario: that of a miniature cosmic laboratory.
However, Avi Loeb proposes a bolder step. In a new essay, the Harvard astrophysicist argues that life could have taken completely different paths in other solar systems. Not only variations in terrestrial biochemistry, but divergent routes, with different solvents, energies and molecular structures. “Not all life forms have to look like us – points out this expert. Some could be invisible to our tools, because we don’t know what to look for.”
Loeb calls divergent life any biological form that is not based on water, DNA or photosynthesis. Imagine, he suggests, a biology based on liquid ammonia, methane or supercritical carbon dioxide, with metal catalysts instead of enzymes. On cold worlds or icy bodies, such systems could evolve slowly, perhaps without the need for oxygen or solar heat.
A comet like 3I/ATLAS, with an unusual combination of CO₂ and ice, could be a stable environment for that alternative chemistry. When rotating, contrasts in temperature and radiation would generate energy gradients (differences that fuel chemical reactions) capable of keeping complex molecules away from equilibrium.
Does this mean that 3I/ATLAS is alive? No. So far, there is no evidence even remotely close. But it is a possible scenario. A reminder that Life, if it is abundant in the cosmos, does not have to follow the same instruction manual as ours.