Free Astronomy Magazine November-December 2025

30 ASTRO PUBLISHING -DECEMBER 2025 Comet’s water holds clues to life on Earth by National Radio Astronomy Observatory N ew research has uncovered compelling evidence that water from a comet is strik- ingly similar to that found in Earth’s oceans, offering fresh support for the idea that comets may have played a crucial role in delivering water—and possibly some of the molecular ingredients for life—to our planet. Using the powerful Ata- cama Large Millimeter/submillime- ter Array (ALMA), an international team of scientists, led by Martin Cordiner of NASA’s Goddard Space Flight Center, mapped the distribu- tion of both ordinary water (H 2 O) and “heavy” water (HDO, which contains the heavier isotope, deu- terium) in the coma (the cloud of gas surrounding the nucleus) of the Halley-type comet 12P/Pons-Brooks during its approach to the Sun. This marks the first time such detailed spatial mapping of these two forms