New research reveals that the mysterious interstellar visitor 3I/ATLAS, which has intrigued astronomers and space enthusiasts alike for the better part of a year, comes from a very cold alien environment.
According to new research from the University of Michigan, published in Nature Astronomy, 3I/ATLAS comes from a much colder region with significantly less radiation than our solar system, marking a breakthrough in the characterization of these interstellar objects.
This assertion is based on an analysis of the water 3I/ATLAS has released during its journey through our solar system, which showed it contained deuterium, also known as heavy hydrogen.
Strange Water on 3I/A
“Our new observations show that the conditions that led to the formation of our solar system are much different from how planetary systems evolved in different parts of our galaxy,” said lead author Luis Salazar Manzano.
Deuterium is a stable Hydrogen isotope with one proton and one neutron, unlike most hydrogen atoms, which have only a proton. Hydrogen, as most are aware, is one of the two ingredients in water’s H2O formula. Heavy water like this, containing high levels of deuterium, does exist on Earth, but it is relatively rare compared to its proportion on 3I/A. In fact, the amount of deuterium is 40 times as much as on Earth, and 30 times as much as on any other known comet.
Earlier this year, The Debrief reported on the high volume of deuterium present on 3I/ATLAS. The new research essentially builds on those findings, which are helping bring more clarity to the unusual origins of the most mysterious interstellar object observed to date.
“The amount of deuterium with respect to ordinary hydrogen in water is higher than anything we’ve seen before in other planetary systems and planetary comets,” Salazar Manzano said.
Following 3I/ATLAS
The researchers note that it was fortunate that 3I/ATLAS came to the attention of astronomers so early in its approach to our solar system. The University of Michigan team had enough advance notice to secure observation time at Arizona’s MDM Observatory, allowing them to make some of the earliest observations of gas emission from 3I/ATLAS.
They followed up by moving their work to Chile’s Atacama Large Millimeter/submillimeter Array, or ALMA, providing essential tools for analyzing the comet’s chemical makeup. ALMA’s extreme sensitivity enabled the team to separate deuterated water from conventional water at such high resolution that it could accurately determine their ratio.
This marked a notable first, as it had never been accomplished previously with an interstellar object.
“Being at the University of Michigan and having access to these facilities was the key to making this work possible,” Salazar Manzano said. “We were part of a team that was very talented and very experienced in multiple areas, all of us complemented each other and that’s what allowed us to analyze and interpret these data sets.”
Where 3I/ATLAS Formed
Examining this unusual water makeup provided the University of Michigan researchers with clues about the type of environment 3I/ATLAS originated in. Crucially, the researchers compared this evidence with the conditions of our early solar system during its formation, and found stark contrasts between the two.
“This is proof that whatever the conditions were that led to the creation of our solar system are not ubiquitous throughout space,” co-author Teresa Paneque-Carreño said. “That may sound obvious, but it’s one of those things that you need to prove.”
3I/ATLAS is only the third known interstellar object to pass through our solar system, and 1I/ʻOumuamua, the first confirmed interstellar object, was only discovered in 2017. With rapidly advancing sensing capabilities, astronomers expect to discover more of these exotic visitors in the years ahead, and at an increasing rate.
The paper, “Water D/H in 3I/ATLAS as a Probe of Formation Conditions in Another Planetary System,” appeared in Nature Astronomy on April 23, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.