Long before 3I/ATLAS slipped through the inner solar system, its water had already recorded the kind of place it came from. That record now looks extreme. Astronomers studying the interstellar comet say its water contains an unusually heavy form of hydrogen called deuterium at levels far beyond anything measured in comets closer to home. The signal is so strong that it points to a birthplace far colder than the environment that formed Earth, the planets, and the icy bodies that still orbit the Sun. The result offers one of the sharpest chemical glimpses yet into how different other planetary systems may be from our own. “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 Luis Salazar Manzano, lead author of the research and a doctoral student in the University of Michigan’s Department of Astronomy. Interstellar comet 3I/ATLAS carries deuterium-rich water, pointing to a far colder birthplace than our solar system. (CREDIT: Wikimedia / …