Lunar Radiation Environment and Space Weathering from the Cosmic Ray Telescope for the Effects of Radiation (Crater) Nathan A

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Lunar Radiation Environment and Space Weathering from the Cosmic Ray Telescope for the Effects of Radiation (Crater) Nathan A University of New Hampshire University of New Hampshire Scholars' Repository Physics Scholarship Physics 12-1-2012 Lunar radiation environment and space weathering from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) Nathan A. Schwadron University of New Hampshire, [email protected] T. Baker University of New Hampshire B. Blake A. W. Case J. F. Cooper See next page for additional authors Follow this and additional works at: https://scholars.unh.edu/physics_facpub Part of the Physics Commons Recommended Citation Schwadron, N. A., et al. (2012), Lunar radiation environment and space weathering from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER), J. Geophys. Res., 117, E00H13, doi:10.1029/2011JE003978. This Article is brought to you for free and open access by the Physics at University of New Hampshire Scholars' Repository. It has been accepted for inclusion in Physics Scholarship by an authorized administrator of University of New Hampshire Scholars' Repository. For more information, please contact [email protected]. Authors Nathan A. Schwadron, T. Baker, B. Blake, A. W. Case, J. F. Cooper, M. Golightly, Andrew P. Jordan, Colin J. Joyce, J. Kasper, K. Kozarev, J. Mislinski, J. Mazur, and Harlan E. Spence This article is available at University of New Hampshire Scholars' Repository: https://scholars.unh.edu/physics_facpub/179 JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 117, E00H13, doi:10.1029/2011JE003978, 2012 Lunar radiation environment and space weathering from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) N. A. Schwadron,1,2 T. Baker,1,2 B. Blake,3 A. W. Case,4 J. F. Cooper,5 M. Golightly,1,2 A. Jordan,1,2 C. Joyce,1 J. Kasper,4 K. Kozarev,4,6 J. Mislinski,1,2 J. Mazur,7 A. Posner,8 O. Rother,9,10 S. Smith,1,2 H. E. Spence,1,2 L. W. Townsend,11 J. Wilson,1,2 and C. Zeitlin12 Received 29 September 2011; revised 27 December 2011; accepted 8 January 2012; published 13 March 2012. [1] The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) measures linear energy transfer by Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs) on the Lunar Reconnaissance Orbiter (LRO) Mission in a circular, polar lunar orbit. GCR fluxes remain at the highest levels ever observed during the space age. One of the largest SEP events observed by CRaTER during the LRO mission occurred on June 7, 2011. We compare model predictions by the Earth-Moon-Mars Radiation Environment Module (EMMREM) for both dose rates from GCRs and SEPs during this event with results from CRaTER. We find agreement between these models and the CRaTER dose rates, which together demonstrate the accuracy of EMMREM, and its suitability for a real-time space weather system. We utilize CRaTER to test forecasts made by the Relativistic Electron Alert System for Exploration (REleASE), which successfully predicts the June 7th event. At the maximum CRaTER-observed GCR dose rate (11.7 cGy/yr where Gy is a unit indicating energy deposition per unit mass, 1 Gy = 1 J/kg), GCRs deposit 88 eV/ molecule in water over 4 billion years, causing significant change in molecular composition and physical structure (e.g., density, color, crystallinity) of water ice, loss of molecular hydrogen, and production of more complex molecules linking carbon and other elements in the irradiated ice. This shows that space weathering by GCRs may be extremely important for chemical evolution of ice on the Moon. Thus, we show comprehensive observations from the CRaTER instrument on the Lunar Reconnaissance Orbiter that characterizes the radiation environment and space weathering on the Moon. Citation: Schwadron, N. A., et al. (2012), Lunar radiation environment and space weathering from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER), J. Geophys. Res., 117, E00H13, doi:10.1029/2011JE003978. 1. Introduction radiation behind a “human tissue-equivalent” plastic [Spence et al., 2010]. CRaTER provides the fundamental measure- [2] Galactic Cosmic Rays (GCRs) and Solar Energetic ments needed to test our understanding of the lunar radiation Particles (SEPs) present formidable hazards for human environment. exploration, mission and spacecraft operations. The Cosmic [3] The current evolution of the Sun between solar cycles Ray Telescope for the Effects of Radiation (CRaTER) 23 and 24 remains highly anomalous compared to previous instrument on the Lunar Reconnaissance Orbiter (LRO) periods of the space age. The Sun has been abnormally quiet mission characterizes the global lunar radiation environment over a relatively long solar minimum when GCRs achieved and its biological impacts by measuring GCR and SEP the highest flux levels observed in the space age [Mewaldt 1EOS Space Science Center, University of New Hampshire, Durham, 6Department of Astronomy, Boston University, Boston, Massachusetts, New Hampshire, USA. USA. 2Institute for the Study of Earth, Oceans, and Space, University of New 7Space Science Department, Aerospace Corporation, Chantilly, Hampshire, Durham, New Hampshire, USA. Virginia, USA. 3Space Science Department, Aerospace Corporation, Los Angeles, 8NASA Headquarters, Washington, D. C., USA. California, USA. 9Scientific Data Processing, Kiel, Germany. 4Harvard-Smithsonian Center for Astrophysics, Cambridge, 10Institut für Experimentall und Angewandte Physik, Christian- Massachusetts, USA. Albrechts Universität Kiel, Kiel, Germany. 5Heliospheric Physics Laboratory, NASA Goddard Space Flight Center, 11Department of Nuclear Engineering, University of Tennessee, Greenbelt, Maryland, USA. Knoxville, Tennessee, USA. 12Space Science and Engineering Division, Southwest Research Copyright 2012 by the American Geophysical Union. Institute, Boulder, Colorado, USA. 0148-0227/12/2011JE003978 E00H13 1of13 E00H13 SCHWADRON ET AL.: LUNAR RADIATION AND SPACE WEATHERING E00H13 et al., 2010], and the power, pressure, flux and magnetic [7] PREDICCS also includes a new method for forecast- flux of solar wind were at the lowest levels [McComas et al., ing the radiation environment. Posner [2007] showed how 2008; Schwadron et al., 2008; Connick et al., 2011]. Even relativistic electrons provide up to 1-h advanced warning observations of the global heliosphere show remarkably of the arrival time and intensity of the SEP ions. Observation rapid changes [McComas et al., 2010] caused by dropping of these relativistic electrons provides the basis for a real- solar wind pressure. This new period of solar evolution time forecasting system called the Relativistic Electron Alert presents a unique opportunity to study the doses of GCRs System for Exploration (REleASE) [Posner et al., 2009] when their fluxes remain at high levels. By relating GCRs to (Figure 1). After one year of operation at partner institutes at neutron fluxes observed from ground-based monitors and to the Christian Albrechts University in Kiel, Germany and at GCR fluxes observed by other spacecraft such as Advanced NASA’s (Community Coordinated Modeling Center) Composition Explorer (ACE), we develop the capability to CCMC, REleASE showed sensitivity to relatively small project GCR dose rates from the present period back through events and yielded low false alarm rates. Here, we use time when different interplanetary conditions prevailed. CRaTER observations (SEP radiation dose) along with the [4] Major advances made over the last decade in physics- REleASE model and the Comprehensive Suprathermal and based numerical modeling of the coupled Sun-to-Earth Energetic Particle Analyzer (COSTEP) [Muller-Mellin et al., system now provide meaningful opportunities to use 1995] observations from SOHO (which measures relativistic models in a predictive sense. Many agencies have prioritized electrons) to verify, validate, and refine the model. The goal predictive capabilities to serve their user communities is to improve the reliability and thus value of the REleASE [Spence et al., 2004], including NOAA’s Space Weather model toward realizing the up to 1-h forecast of SEP events, Prediction Center and NASA’s Space Radiation Analysis a critical improvement over current forecasting. Group at Johnson Space Center. An accurate warning sys- [8] In addition to the hazards they pose, GCRs are also an tem for SEP radiation hazards is critical in view of NASA’s important energy source for space weathering, the general plans to send astronauts beyond low-Earth orbit. Demon- process of planetary surface and atmospheric modification strating this commitment to the future of human exploration, by space environmental components including micromete- NASA officially named the MultiPurpose Crew Vehicle that oroid bombardment, solar ultraviolet irradiation, solar wind could take its astronauts back to the Moon, to Mars and to and magnetospheric plasma, and more energetic charged and asteroids (see NASA, Preliminary report regarding NASA’s neutral particles including GCRs. The plasma-surface inter- space launch system and multi-purpose crew vehicle, pur- action processes [Johnson, 1990] can act to produce a thin suant to section 309 of the NASA Authorization Act of layer of outer material covering and sometimes obscure the 2010 (P.L. 111-267), January 2011). However, space radi- endogenic materials of greatest interest for understanding ation remains a major factor for risk mitigation of safe deep origins and interior evolution of the affected object. Within a space travel [Cucinotta et al., 2010] and models of space series of weathered layers at increasing depth, products of radiation effects including dose and dose-equivalent
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