In November 2025, scientists seized a historic opportunity when the interstellar comet 3I/ATLAS passed between ESA’s Jupiter Icy Moons probe (JUICE) and NASA’s Europa Clipper spacecraft. This unique alignment allowed one spacecraft to capture the comet’s dazzling dayside while the other focused on its dusty nightside.
In November 2025, 3I/ATLAS passed between ESA’s Juice spacecraft and NASA’s Europa Clipper spacecraft. Image credit: NASA/ESA/Southwest Research Institute.
“As the comet journeyed between Juice and Europa Clipper, we successfully coordinated informal observations between the two spacecraft,” stated Dr. Kurt Retherford, a planetary researcher at the Southwest Research Institute.
“We notably observed emissions of hydrogen, oxygen, and carbon,” he added.
“These elements arise when gases leaking from a comet’s core break down into atoms upon exposure to sunlight.”
This exceptional observation leveraged the ultraviolet spectrometer (UVS) instruments aboard both the Juice and Europa Clipper spacecraft.
“Studying interstellar comets has provided exciting bonus science,” remarked Dr. Philippa Molyneux, also from the Southwest Research Institute.
“The resulting rare data set includes valuable insights into gas emissions and airborne dust.”
“This marks the first instance of directly observing the coma of a gas-emitting comet from two perspectives simultaneously.”
“While Europa Clipper captured the comet’s night side, abundant with dust, Juice documented the glowing gas of the day side.”
Early findings indicated that carbon emissions from 3I/ATLAS were unexpectedly high compared to typical solar system comets, corroborating other observations regarding the origin and composition of interstellar comets.
By examining trends in emissions over multiple days, researchers can track changes in the molecular ratio as the comet traverses the solar system.
“Studying the ratio of water ice to dry ice allows us to compare this interstellar comet’s composition with those from our solar system,” Molyneux explained.
“This analysis will illuminate whether the solar system in which 3I/ATLAS formed is similar to or different from our own.”
“I found the collaboration with Europa Clipper to be a rewarding demonstration of how both projects can synergize their observation programs,” Dr. Retherford commented.
“The SwRI team is involved in both missions, making this a special highlight in our collaborative efforts.”
Source: www.sci.news
