Back to Search
Start Over
Herschelmeasurements of the D/H and16O/18O ratios in water in the Oort-cloud comet C/2009 P1 (Garradd)
- Source :
- Astronomy and Astrophysics-A&A, Astronomy and Astrophysics-A&A, 2012, 544, pp.L15. ⟨10.1051/0004-6361/201219744⟩, Astronomy and Astrophysics-A&A, EDP Sciences, 2012, 544, pp.L15. ⟨10.1051/0004-6361/201219744⟩
- Publication Year :
- 2012
- Publisher :
- EDP Sciences, 2012.
-
Abstract
- The D/H ratio in cometary water is believed to be an important indicator of the conditions under which icy planetesimals formed and can provide clues to the contribution of comets to the delivery of water and other volatiles to Earth. Available measurements suggest that there is isotopic diversity in the comet population. The Herschel Space Observatory revealed an ocean-like ratio in the Jupiter-family comet 103P/Hartley 2, whereas most values measured in Oort-cloud comets are twice as high as the ocean D/H ratio. We present here a new measurement of the D/H ratio in the water of an Oort-cloud comet. HDO, H_2O, and H_2^18O lines were observed with high signal-to-noise ratio in comet C/2009 P1 (Garradd) using the Herschel HIFI instrument. Spectral maps of two water lines were obtained to constrain the water excitation. The D/H ratio derived from the measured H_2^16O and HDO production rates is 2.06+/-0.22 X 10**-4. This result shows that the D/H in the water of Oort-cloud comets is not as high as previously thought, at least for a fraction of the population, hence the paradigm of a single, archetypal D/H ratio for all Oort-cloud comets is no longer tenable. Nevertheless, the value measured in C/2009 P1 (Garradd) is significantly higher than the Earth's ocean value of 1.558 X 10**-4. The measured H_2^16O/H_2^18O ratio of 523+/-32 is, however, consistent with the terrestrial value.<br />Comment: 6 pages with 4 figures and 1 table. Accepted for publication as a Letter in Astronomy & Astrophysics
- Subjects :
- Earth and Planetary Astrophysics (astro-ph.EP)
[PHYS]Physics [physics]
Physics
education.field_of_study
Planetesimal
010504 meteorology & atmospheric sciences
Population
Comet
FOS: Physical sciences
Astronomy and Astrophysics
Astrophysics
01 natural sciences
Space observatory
13. Climate action
Space and Planetary Science
0103 physical sciences
Water excitation
[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
education
010303 astronomy & astrophysics
ComputingMilieux_MISCELLANEOUS
Astrophysics - Earth and Planetary Astrophysics
0105 earth and related environmental sciences
Subjects
Details
- ISSN :
- 14320746 and 00046361
- Volume :
- 544
- Database :
- OpenAIRE
- Journal :
- Astronomy & Astrophysics
- Accession number :
- edsair.doi.dedup.....f2a0fa95218fea299ff7d05e1d6fb6d8