© 2019 - All Rights Reserved
|Scientists from NASA’s Goddard Center for Astrobiology observed the comet C/2014 Q2 – also called Lovejoy – and made simultaneous measurements of the output of H2O and HDO, a variant form of water. This image of Lovejoy was taken on Feb. 4, 2015 — the same day the team made their observations and just a few days after the comet passed its perihelion, or closest point to the sun. Credit: Courtesy of Damian Peach|
“The change we saw with this comet is surprising, and highlights the need for repeated measurements of D-to-H in comets at different positions in their orbits to understand all the implications,” said Lucas Paganini, a researcher with the Goddard Center for Astrobiology and lead author of the study, available online in the Astrophysical Journal Letters.
“If the D-to-H value changes with time, it would be misleading to assume that comets contributed only a small fraction of Earth’s water compared to asteroids,” Paganini said, “especially, if these are based on a single measurement of the D-to-H value in cometary water.”
“Comets can be quite active and sometimes quite dynamic, especially when they are in the inner solar system, closer to the sun,” said Michael Mumma, director of the Goddard Center for Astrobiology and a co-author of the study. “The infrared technique provides a snapshot of the comet’s output by measuring the production of H2O and HDO simultaneously. This is especially important because it eliminates many sources of systematic uncertainty.”