<\/p>\n The SPHEREx images were taken as the comet was already heading back out of the inner solar system. Instead of fading quietly into the dark, 3I\/ATLAS<\/a> flared with activity, developing a glowing coma rich in water vapor, carbon dioxide and organic compounds. Observations also show a pear-shaped dust tail, created by rocky material being ejected as the comet’s activity increases.<\/p>\n You may like<\/p>\n “Comet 3I\/ATLAS<\/a> was full-on erupting into space in December 2025, after its close flyby of the sun, causing it to significantly brighten,” Carey Lisse, lead author of the study, said in the statement. “Even water ice was quickly sublimating into gas in interplanetary space.”<\/p>\n Discovered in July 2025 by the ATLAS asteroid survey, 3I\/ATLAS is only the third confirmed interstellar object ever spotted passing through our solar system, following 1I\/’Oumuamua<\/a> in 2017 and 2I\/Borisov<\/a> detected in 2019. Unlike its predecessors, however, 3I\/ATLAS put on an extended chemical show that SPHEREx was uniquely equipped to observe.<\/p>\n SPHEREx studies the universe in infrared light, allowing scientists to identify not just dust, but also a detailed mix of molecules streaming off the comet<\/a> \u2014 including water ice, carbon dioxide, methane, methanol and cyanide, which are substances that serve as key ingredients in planetary formation.<\/p>\n While comets typically become most active near perihelion<\/a>, when solar heat causes surface ices to vaporize, the SPHEREx data shows that 3I\/ATLAS intensified well after that point. This suggests sunlight slowly penetrated beneath the comet’s surface before triggering a delayed release of buried, ancient ices, according to the statement.<\/p>\n “Since comets consist of about one-third bulk water ice, it was releasing an abundance of new, carbon-rich material that had remained locked in ice deep below the surface,” Lisse said in the statement. “We are now seeing the usual range of early solar system<\/a> materials, including organic molecules, soot, and rock dust, that are typically emitted by a comet.”<\/p>\n Because 3I\/ATLAS originated beyond our solar system, its chemistry offers a rare chance to compare our local comets with icy bodies formed around other stars<\/a>. The similarities and differences could help scientists determine whether the raw materials for planets and potentially life are common throughout the Milky Way.<\/p>\n \n
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