SETI Scientists Searched Interstellar Comet 3I/ATLAS for Alien Signals

Interstellar comet 3I/ATLAS, the third object from outside our solar system ever seen, was found in July 2025 by the ATLAS telescope set-up in Chile. It was moving at about 137,000 miles per hour, and that speed just pulled instant scientific focus. People at the SETI Institute, not long ago, checked it for possible man-made radio transmissions, or what they call techno-signatures. No signals showed up, yet the study still helped sharpen our skills for spotting whatever might be alien tech.

A Comet From Another World

According to Space.com, multiple lines of evidence show that 3I/ATLAS is natural. It has an orbital eccentricity of 6.137, which is way beyond what we see for any comet in our solar system, proving its interstellar origin. In late 2025, the ALMA telescope spotted an extremely high amount of methanol in its coma, the bright gas that appears as sunlight heats its icy surface. The methanol was more than what we typically find in most comets in our solar system. Plus, it had frozen carbon dioxide, too. These chemicals suggest that 3I/ATLAS formed in a colder environment in a very different planetary system from ours.

Silence in the Radio Band

Using the Allen Telescope Array in Northern California, researcher Sofia Sheikh and her team spent over seven hours scanning 3I/ATLAS across 1 to 9 GHz, hunting for narrowband radio signals — a class of emission with no known natural origin. Nearly 74 million candidate signals were systematically filtered for terrestrial interference and satellite contamination, leaving none unexplained. The study placed an upper limit of 10–110 watts on any transmitter aboard the object, the power of a household appliance.