Dr. Alice Stephant
As a cosmochemist, my expertise focuses on the isotopic study of various extraterrestrial samples, from chondrites to lunar or martian samples, including primitive achondrites.
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The purpose of my studies is to understand the origin and distribution of water in the inner solar system, in order to better understand the origin of water on Earth, necessary for the emergence of life.
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I am a specialist in microscopy (SEM), chemical analyses (EPMA) and isotopic analyses (SIMS).
Research
My research focuses on the study of hydrogen isotopes and water contents of various extraterrestrial samples, in order to determine the abundance and origin of water from their parent bodies. Water is perhaps one of the most important molecules in our Solar System, and determining its origin and distribution in planetary bodies has many implications for the origin and evolution of those bodies.
The moon
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Due to its formation model, the Moon has long been considered devoid of water. Nevertheless, the analysis of lunar meteorites and samples brought back by the Apollo missions have demonstrated that the lunar mantle is not entirely dry. Moreover, strong heterogeneities in isotopic composition of hydrogen and in water content are observed among the various lunar lithologies. The origin of endogenous water on the Moon and that of its heterogeneities is raised. To answer this question, various phases and minerals can be analysed: apatites, melt inclusions and nominally anhydrous minerals.
Vesta and Eucrites
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Eucrites are one of meteorite groups that have been genetically linked to the asteroid Vesta, together with diogenites and howardites. Some of these meteorites formed only a few million years after the formation of the refractory inclusions. The presence of water in these meteorites, and therefore in Vesta, indicates that water was incorporated very early in certain protoplanetary bodies of our solar system. This water could have a hydrogen isotope ratio approaching the nebular value, indicating a possible contribution of nebular hydrogen rather than a chondritic contribution.
Primitive achondrites
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Primitive achondrites are transitional between chondrites and achondrites, and as such, they recorded the first steps of planetary differentiation. Winonaites and acapulcoites are two groups of primitive achondrites that share many common characteristics, making their classification sometimes difficult. The mineralogical, chemical and isotopic study of some members of these meteorite groups suggests that they do not fit into the current dichomoty classification of winonaites and acapulcoites, suggesting the existence of another group of primitive achondrites.
Techniques
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All of these studies require the preparation of terrestrial standards and extraterrestrial samples, as well as the development of NanoSIMS measurement protocols in order to push the limits of current analysis capabilities.
Employment history
Professional activities
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ExMAG executive committee member (Lunar and Planetary Institute).
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Scientific journal reviewer (eg, Nature geosciences, Geochimica et Cosmochimica Acta, The Planetary Science Journal, Earth and Planetary Science Letters, Meteoritics and Planetary Science).
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Travel Awards Committee - Meteoritical Society Meeting, Chicago, (08/2021).
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Science Organizing Committee - 9th European Lunar Symposium, Virtual (07/2021).
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Co-Chair of the Scientific Organizing Committee - 8th European Lunar Symposium, Virtual (05/2020).
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Organizing team (4 members) – The Royal Society Summer Exhibition - London (1-7 July 2019) including 5 UK institutions (~10,000 visitors).
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Lead organizing member of the Moon Night event at the Open University (12/2018 ~200 visitors).
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Science Organizing Committee - 6th European Lunar Symposium, Toulouse, France (05/ 2018).
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Organization of Cosmochemical Research Group meetings, the Open University (2017-2019).
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Outreach events in Phoenix schools, Phoenix Comicon and at Arizona State University, USA (2015-2017).
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NASA NSPIRES Cosmochemistry reviewer and executive secretary (2016).
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​ Organization and participation in the opening science days of the Museum laboratories, MNHN, France (2011-2014).
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Teaching classes for master and graduate students, meteorite microscopy, MNHN, France (2013-2014).
Publications
16- ​​Stephant A. and Davidson J. Tissemouminites: A new group of primitive achondrites. 2023. Elements, Mineralogical Society of America, 197-198.
15- ​​Cristian C., Barbaro A., Murri M., Domeneghetti M.C., Langone A., Bruschini E., Stephant A., Alvaro M., Stefani S., Cuppone T., Casalini M., Migliorini A., Roush T.L., Giovanni P. Al Huwaysah 010: the most reduced brachinite, so far, 2023. Meteoritics & Planetary Science.
14- ​​Stephant A., Zhao X., Anand M., Davidson J., Carli C., Cuppone T., Pratesi G., Franchi I.A. Hydrogen in acapulcoites and lodranites: A unique source of water for planetesimals in the inner Solar System, 2023. Earth and Planetary Science Letters, 615, 118202
13- Stephant A., Carli C., Anand M, Néri A., Davidson J., Pratesi G., Cuppone T., Greenwood R.C., Franchi I.A. Tissemouminites: a new group of primitive achondrites spanning the transition between acapulcoites and winonaites. Meteoritics & Planetary Science, Article DOI: 10.1111/MAPS.13944
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12- Stephant A. , Wadhwa M., Hervig R., Bose M., Zhao X., Barrett TJ, Anand M., Franchi IA Deuterium-poor water reservoir in the asteroid 4 Vesta and the inner Solar System, 2021. Geochimica and Cosmochimica Acta, 297, 203-219.
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11- Chan QHS, Stephant A. , Franchi IA, Zhao X., Brunetto R., Kebukawa Y., Noguchi T., Johnson D., Price MC, Harriss KH, Zolensky ME, Grady MM Organic matter and water from asteroid Itokawa, 2021. Scientific Reports , 11, 1, 1-12.
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10- Davidson J., Wadhwa M., Hervig RL, Stephant A. Water on Mars: Insights from apatite in regolith breccia Northwest Africa 7034, 2020. Earth and Planetary Science Letters, 552, 116597.
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9- Stephant A. , Anand M., Zhao X., Degli-Alessandrini G., Tartese R., Franchi IA The hydrogen isotope composition of lunar melt inclusions: An interplay of complex magmatic and secondary processes, 2020. Geochimica and Cosmochimica Acta , 284, 196-221.
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8- Cernok A., Anand M., Darling J., Zhao X., White L., Stephant A. , Dunlop J., Whitehouse M., Franchi IA Lunar apatite - A reliable shock-resistant hygrometer and impact-sensitive Pb-Pb chronometer?, 2020, Earth and Planetary Science Letters, 544, 116364.
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7- Chan QHS, Franchi IA, Zhao X., Stephant A. , Wright IP, Alexander CMO'D. Organics preserved in anhydrous interplanetary dust particles: pristine or not?, 2020. Meteoritics and Planetary Science, 55, 6, 1320-1348.
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6- Stephant A. , Anand M., Ashcroft HO, Zhao X., Hu S., Korotev RL, Strekopytov S., Greenwood RC, Humphreys-Williams E., Liu Y., Tang G., Li Q., Franchi IA An ancient reservoir of volatiles in the Moon sampled by lunar meteorite NWA 10989, 2019. Geochimica et Cosmochimica Acta, 266, 163-183.
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5- Stephant A. , Anand M., Zhao X., Chan Q., Bonifacie M. and Franchi I. The chlorine isotopic composition of the Moon: Insights from melt inclusions, 2019. Earth and Planetary Science Letters, 523, 115715.
4- Stephant A. , Garvie LAJ, Mane P., Hervig R., Wadhwa M. Terrestrial weathering of Tissint causes rapid changes of meteoritic hydrogen isotopes and concentrations, 2018. Scientific Reports, 8:12385.
3- Stephant A. , Remusat L. and Robert, F. Water in type I chondrules of Paris CM chondrite, 2016. Geochimica and Cosmochimica Acta, 199, 75-90.
2- Stephan A. and Robert F. The negligible chondritic contribution in the lunar soils water, 2014.
Proceedings of the National Academy of Sciences of the United States of America, 111, 42.
1- Stephant A. , Remusat L., Thomen A., Robert F. Reduction of OH contamination in quantification of water contents using NanoSIMS imaging, 2014, Chemical Geology, 350, pp 20-26.
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Contact
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