@article{522901c5f7f147339b156c202e37b4ef,
title = "Water ice and organics on the surface of the asteroid 24 Themis",
abstract = "It has been suggested1-3 that Earthg's current supply of water was delivered by asteroids, some time after the collision that produced the Moon (which would have vaporized any of the pre-existing water). So far, no measurements of water ice on asteroids have been made, but its presence has been inferred from the comet-like activity of several small asteroids, including two members of the Themis dynamical family6. Here we report infrared spectra of the asteroid 24 Themis which show that ice and organic compounds are not only present on its surface but also prevalent. Infrared spectral differences between it and other asteroids make 24 Themis unique so far, and our identification of ice and organics agrees with independent results that rule out other compounds as possible sources of the observed spectral structure. The widespread presence of surface ice on 24 Themis is somewhat unexpected because of the relatively short lifetime of exposed ice at this distance (∼3.2 au) from the Sun. Nevertheless, there are several plausible sources, such as a subsurface reservoir that brings water to the surface through' impact gardeningg' and/or sublimation.",
author = "Humberto Campins and Kelsey Hargrove and Noemi Pinilla-Alonso and Howell, {Ellen S.} and Kelley, {Michael S.} and Javier Licandro and T. Moth{\'e}-Diniz and Y. Fern{\'a}ndez and Julie Ziffer",
note = "Funding Information: Acknowledgements H.C. and K.H. are visiting astronomers at the Infrared Telescope Facility (IRTF), which is operated by the University of Hawaii under cooperative agreement no. NCC 5-538 with NASA. All the observations used in this publication were obtained at the IRTF. H.C. acknowledges support from NASA{\textquoteright}s Planetary Astronomy programme and from the US National Science Foundation. H.C. was a visiting Fulbright Scholar at the {\textquoteleft}{\textquoteleft}Instituto de Astrof{\'i}sica de Canarias{\textquoteright}{\textquoteright} in Tenerife, Spain, and a visiting astronomer at Observatoire de la C{\^o}te d{\textquoteright}Azur, Nice, France. J.L. acknowledges support from the Spanish {\textquoteleft}Ministerio de Ciencia e Innovaci{\'o}n{\textquoteright}. T.M.-D. was supported by the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico and by the Fundac¸{\~a}o de Amparo {\`a} Pesquisa do Estado do Rio de Janeiro. We benefited from discussions with D. Cruikshank, M. Delb{\'o}, P. Michel, A. Morbidelli and T. Roush.",
year = "2010",
month = apr,
day = "29",
doi = "10.1038/nature09029",
language = "English (US)",
volume = "464",
pages = "1320--1321",
journal = "Nature",
issn = "0028-0836",
publisher = "Nature Publishing Group",
number = "7293",
}