An international team led by Martin Cordiner of NASA's Goddard Space Flight Center mapped ordinary water (H2O) and heavy water (HDO) in the comet's coma during its approach to the Sun. This marks the first detailed spatial mapping of both water types in a comet.
The ALMA data were paired with NASA Infrared Telescope Facility (IRTF) measurements to determine the comet's deuterium-to-hydrogen (D/H) ratio, a key chemical marker of water's origin. The result, (1.71+/-0.44)+ 10-4, is the lowest D/H ratio ever recorded in a Halley-type comet and aligns closely with Earth's oceans.
"Comets like this are frozen relics left over from the birth of our Solar System 4.5 billion years ago," Cordiner said. "Our new results provide the strongest evidence yet that at least some Halley-type comets carried water with the same isotopic signature as that found on Earth, supporting the idea that comets could have helped make our planet habitable."
Halley-type comets, with orbital periods between 20 and 200 years, rarely enter the inner Solar System. Past comet studies often showed mismatched D/H ratios, leaving the role of comets in delivering Earth's water uncertain. These new findings point to 12P/Pons-Brooks as a potential contributor of water and life-essential compounds to early Earth.
Mapping also confirmed the gases originated from the comet's nucleus rather than forming in its surrounding gas cloud. "By mapping both H2O and HDO in the comet's coma, we can tell if these gases are coming from the frozen ices within the solid body of the nucleus," said NASA's Stefanie Milam, a study co-author.
ALMA's sensitivity enabled detection of faint heavy water emissions from deep within the coma-an observational first for any comet.
Research Report:A D/H ratio consistent with Earth's water in Halley-type comet 12P from ALMA HDO mapping
Related Links
Atacama Large Millimeter/submillimeter Array (ALMA)
Asteroid and Comet Mission News, Science and Technology
| Subscribe Free To Our Daily Newsletters |
| Subscribe Free To Our Daily Newsletters |
