Press Release

First Results of the ROSINA Instrument

By SpaceRef Editor
December 11, 2014
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First measurements by the Rosetta mission’s ROSINA instrument show that the deuterium-to-hydrogen (D/H) ratio of the comet 67P/Churyumov-Gerasimenko is highly enriched in deuterium. These results contradict the theory that the water present in the Earth’s atmosphere and oceans has a cometary origin. They also indicate that 67P comets do not all come from one region, the Kuiper Belt: some may have originated in the Oort Cloud. This international study, which involved laboratories from the CNRS, Université Toulouse III — Paul Sabatier, UPMC, UVSQ, Université d’Orléans, Université de Lorraine and Université de Franche-Comté, with support from CNES, is published in Science Express on 10 December 2014.

Born 4.55 billion years ago, the various bodies that make up the solar system — the Earth and planets, asteroids and comets — originally formed from the same cloud of gas and dust, the protosolar nebula. From this common origin they have developed in different ways, depending on their orbit and therefore on their exposure to solar radiation. Comets, which have been at great distances from the Sun for most of their lives, have hardly changed at all, and are thus privileged witnesses of the conditions that prevailed at the birth of the solar system. The isotopic compositions of their principal constituents are therefore likely to provide unique information about the conditions and processes underlying the formation of the solar system, and especially about the origin of the Earth’s water.

The D/H ratio is a key marker for determining the origin of the Earth’s water and understanding the role that the comets and/or asteroids may have played. The detailed study of the first spectra obtained by the ROSINA instrument since it arrived in the neighborhood of the comet gives a value for the D/H ratio of 5.3 ± 0.7 x 10^-4, whereas its value on Earth is 1.55 x 10^-4. This ratio, highly enriched in deuterium in comparison with the Earth, therefore conflicts with the assumption that the water present in the Earth’s atmosphere and oceans has a cometary origin, contrary to what other results from Jupiter family comets suggested. Since the value of the terrestrial D/H ratio falls within the range of the D/H ratio of asteroids located between Mars and Jupiter, the water in the Earth’s oceans may have come mainly from asteroids and/or certain comets. In addition, cometary reservoirs are located at considerable distances from the Sun: the Oort Cloud, for instance, stretches out to over 10^5 AU, and is the source of long-period comets such as Halley. The Kuiper Belt, located at a distance of over 50 AU, is known to be the origin of the comets of the 67P/Churyumov-Gerasimenko family, known as Jupiter family comets since the distant part of their orbits are in the neighborhood of Jupiter’s orbit. According to ROSINA’s new results, the comets in this family may not all come from a single source region, the Kuiper Belt: some may have originated in the Oort Cloud.

The researchers now aim to continue elucidating the chemical and isotopic composition of the atmosphere of 67P/Churyumov-Gerasimenko’s, especially for gaseous species other than hydrogen, such as noble gases and nitrogen. These measurements should make it possible to undertake a detailed exploration of the origin of the volatile elements on Earth that allowed the emergence of life.

“67P/Churyumov-Gerasimenko, a Jupiter Family Comet with a high D/H ratio,” Altwegg K., H. Balsiger, A. Bar-Nun, J.J. Berthelier, A. Bieler, P. Bochsler, C. Briois, U. Calmonte, M. Combi, J. De Keyser, P. Eberhardt, B. Fiethe, S. Fuselier, S. Gasc, T. I. Gombosi, K.C. Hansen, M. Hässig, A. Jäckel, E. Kopp, A. Korth, L. LeRoy, U. Mall, B. Marty, O. Mousis, E. Neefs, T. Owen, H. Rème, M. Rubin, T. Sémon, C.-Y. Tzou, H. Waite, P. Wurz. Science Express, 11 December 2014 [].

The French researchers involved in Rosetta’s ROSINA instrument work at the:
* Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS, CNRS/UPMC/UVSQ),
* Institut de Recherche en Astrophysique et Planétologie (IRAP, CNRS/Université Toulouse III-Paul Sabatier).
Right from the start, both these laboratories played a major role in the ROSINA experiment, whose Principal Investigator is Pr Kathrin Altwegg from the University of Berne.
* Laboratoire de Physique et Chimie de l’Environnement et de l’Espace (LPC2E, CNRS/Université d’Orléans),
* Center de Recherches Pétrographiques et Géochimiques (CRPG, CNRS/Université de Lorraine),
* Laboratoire Univers, Transport, Interfaces, Nanostructures, Atmosphère et Environnement, Molécules (Institut UTINAM, CNRS/Université de Franche-Comté).

The work received backing in particular from CNES, ESA and ERC.

Companion press release from ESA:

Companion press release from JPL:

SpaceRef staff editor.