Comet 3I/ATLAS is an interstellar traveler, visiting our solar system from another part of the galaxy. While its place of origin remains a mystery, astronomers believe it was formed under conditions far cooler than those of our own planetary system.
Writing in Nature Astronomy, researchers from the University of Michigan explain that unusually high levels of water containing deuterium (or “heavy hydrogen”) found on the comet highlight the variations that exist within the Milky Way.
“This is proof that whatever the conditions were that led to the creation of our solar system are not ubiquitous throughout space,” Teresa Paneque-Carreño, a professor of astronomy at the University of Michigan, who co-led the study, said in a press release. “That may sound obvious, but it’s one of those things that you need to prove.”
Composition of Comet 3I/ATLAS For this study, Paneque-Carreño and colleagues analyzed the composition of water on comet 3I/ATLAS. The team was particularly interested in the ratio between conventional water and deuterated water, also known as semi-heavy water.
The difference between the two lies in the hydrogen atom. Water molecules (H2O) in “conventional water” contain one oxygen atom and two hydrogen atoms with a single proton at their core. Sometimes, one of those hydrogen atoms is accompanied by a neutron. Hydrogen that contains this additional neutron is known as deuterium (or “heavy hydrogen”), and water molecules made of deuterium can be described as deuterated water (HDO).
Deuterated water tends to form under extremely low temperatures. Usually, this means temperatures below 30 Kelvin, or about negative 406 degrees Fahrenheit.
While deuterated water is present here on Earth, it exists in very low quantities. Comets in our Solar System contain approximately one molecule of deuterium for every ten thousand molecules of conventional water.
Read More: Interstellar Comet 3I/ATLAS Is Packed With Alcohol — Indicating That It Formed Beyond Our Solar System
Calculating Ratios of Deuterated Water with ALMA The Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile is exceptionally sensitive and capable of detecting tiny variations that enable astronomers to determine ratios between conventional and deuterated water.
The data provided by ALMA suggests the ratio of deuterated water to conventional water on comet 3I/ATLAS is more than 30 times the ratio of any comet found in our solar system and more than 40 times the ratio of water in Earth’s oceans.
“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,” lead author Luis Salazar Manzano, a doctoral student at the University of Michigan’s Department of Astronomy, said in the statement.
According to the researchers, this is the first time an analysis of this kind has been performed on an interstellar object. The findings offer clues to the physical and chemical conditions present in the planetary system when comet 3I/ATLAS was formed and show they must have been “remarkably different from those that shaped Solar System comets,” the researchers wrote.
Specifically, it tells us that the conditions there were cooler than when Earth (and other planets and celestial bodies) were formed in our solar system. There were also lower levels of radiation.
Interstellar Comets, or Fossils from Elsewhere Comet 3I/ATLAS was first detected last summer by the ATLAS survey telescope in Chile. According to NASA, it is hurtling through our solar system at speeds of 137,000 miles (221,000 kilometers) to 152,000 miles (246,000 kilometers) an hour.
To date, it is only the third interstellar comet to have been discovered. But this number is likely to expand, offering new opportunities to understand how different planetary systems evolved.
“Each interstellar comet brings a little bit of its history, its fossils, from elsewhere. We don’t know exactly where, but with instruments like ALMA we can begin to understand the conditions of that place and compare them to our own,” Paneque-Carreño said in a statement.
Read More: New Images of Comet 3I/ATLAS Reveal “How Magical the Universe Could Be”
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This article references information from an article published in Nature Astronomy: Water D/H in 3I/ATLAS as a probe of formation conditions in another planetary system This article references information from NASA: Comet 31/ATLAS Facts and FAQs
https://www.discovermagazine.com/origins-of-comet-3i-atlas-may-have-been-extremely-cold-beyond-our-solar-system-49023
