@article{44ce4d37712146a5b2f83909790d9cd0,
title = "Hexagonal Prisms Form in Water-Ice Clouds on Mars, Producing Halo Displays Seen by Perseverance Rover",
abstract = "Observations by several cameras on the Perseverance rover showed a 22° scattering halo around the Sun over several hours during northern midsummer (solar longitude 142°). Such a halo has not previously been seen beyond Earth. The halo occurred during the aphelion cloud belt season and the cloudiest time yet observed from the Perseverance site. The halo required crystalline water-ice cloud particles in the form of hexagonal columns large enough for refraction to be significant, at least 11 μm in diameter and length. From a possible 40–50 km altitude, and over the 3.3 hr duration of the halo, particles could have fallen 3–12 km, causing downward transport of water and dust. Halo-forming clouds are likely rare due to the high supersaturation of water that is required but may be more common in northern subtropical regions during northern midsummer.",
author = "Lemmon, {M. T.} and D. Toledo and V. Apestigue and I. Arruego and Wolff, {M. J.} and P. Patel and S. Guzewich and A. Colaprete and Vicente-Retortillo and L. Tamppari and F. Montmessin and {de la Torre Juarez}, M. and J. Maki and T. McConnochie and A. Brown and Bell, {J. F.}",
note = "Funding Information: The authors acknowledge and profusely thank the Mars 2020 team from its conception through assembly through operations on Mars. Funding for the U.S.-based authors of this work was provided by the National Aeronautics and Space Administration's Mars 2020 Project, either directly or via subcontracts from the California Institute of Technology's Jet Propulsion Laboratory. The research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). ML is supported by contract 15-712 from Arizona State University and 1607215 from Caltech-JPL. Funding for some Spain-based co-authors was provided by the Spanish Ministry of Economy and Competitiveness, through the projects No. ESP2014-54256-C4-4-R and AYA2015-65041-P; Ministry of Science, Innovation and Universities, projects No. ESP2016-79612-C3-3-, ESP2016-80320-C2-1-R, RTI2018-098728-B-C33 and RTI2018-099825-B-C31; Instituto Nacional de T{\'e}cnica Aeroespacial; Ministry of Science and Innovation's Centre for the Development of Industrial Technology; Grupos Gobierno Vasco IT1366-19; and European Research Council Consolidator Grant No. 818602. A. V.-R. is supported by the Spanish State Research Agency (AEI) Project No. MDM-2017-0737 Unidad de Excelencia “Mar{\'i}a de Maeztu” - Centro de Astrobiolog{\'i}a (INTA-CSIC). Funding Information: The authors acknowledge and profusely thank the Mars 2020 team from its conception through assembly through operations on Mars. Funding for the U.S.‐based authors of this work was provided by the National Aeronautics and Space Administration's Mars 2020 Project, either directly or via subcontracts from the California Institute of Technology's Jet Propulsion Laboratory. The research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). ML is supported by contract 15‐712 from Arizona State University and 1607215 from Caltech‐JPL. Funding for some Spain‐based co‐authors was provided by the Spanish Ministry of Economy and Competitiveness, through the projects No. ESP2014‐54256‐C4‐4‐R and AYA2015‐65041‐P; Ministry of Science, Innovation and Universities, projects No. ESP2016‐79612‐C3‐3‐, ESP2016‐80320‐C2‐1‐R, RTI2018‐098728‐B‐C33 and RTI2018‐099825‐B‐C31; Instituto Nacional de T{\'e}cnica Aeroespacial; Ministry of Science and Innovation's Centre for the Development of Industrial Technology; Grupos Gobierno Vasco IT1366‐19; and European Research Council Consolidator Grant No. 818602. A. V.‐R. is supported by the Spanish State Research Agency (AEI) Project No. MDM‐2017‐0737 Unidad de Excelencia “Mar{\'i}a de Maeztu” ‐ Centro de Astrobiolog{\'i}a (INTA‐CSIC). Publisher Copyright: {\textcopyright} 2022. The Authors.",
year = "2022",
month = sep,
day = "16",
doi = "10.1029/2022GL099776",
language = "English (US)",
volume = "49",
journal = "Geophysical Research Letters",
issn = "0094-8276",
publisher = "American Geophysical Union",
number = "17",
}