Prediction of Martian Surface Neutron Environment

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Prediction of Martian Surface Neutron Environment

• M. S. Clowdsley1, G. DeAngelis2, J. W. Wilson1,
  F. F. Badavi3, and R. C. Singleterry1

1 NASA Langley Research Center, Hampton, VA 2Old
Dominion University, Norfolk, VA 3Christopher
Newport University, Newport News, VA
Solar and Space Physics and the Vision for Space
Exploration Meeting Wintergreen, Virginia October
16-20, 2005
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Radiation Transport Codes

• Monte Carlo Codes MCNPX, HETC, FLUKA, TIGRE
• Accurately model the transport of neutrons,
  protons, and other light ions (and electrons in
  the case of TIGRE)
• GCR ions being added
• Require large amounts of computer time
• Deterministic Codes HZETRN, GRNTRN
• Accurately model the transport of neutrons,
  protons, light ions, and GCR
• Provide rapid transport calculations

HZETRN used in following calculations!!!
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Planetary Surface Material and Atmosphere
Mars Induced Fields
GCR ion
High energy particles
Diffuse neutrons
(Simonsen et al.)
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GCR Environments
Martian Surface
Free Space
1977 Solar Minimum (solid) 1990 Solar Maximum
(dashed)
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Mars Surface Neutrons
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Mars Surface Worst Case SPE Environment
Free Space
Martian Surface
Worst Case SPE 4 X proton component of
Sept. 89
Event Exploration Design Basis SPE as yet
undefined
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Dose Equivalent on Mars Surface Due to GCR
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Mars Surface Mapping
Charged Ions 1977 Solar Minimum
from Space Ionizing Radiation Environment and
Shielding Tools (SIREST) web site
http//sirest.larc.nasa.gov
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Mars Surface Mapping
Neutrons 1977 Solar Minimum
from Space Ionizing Radiation Environment and
Shielding Tools (SIREST) web site
http//sirest.larc.nasa.gov
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Mars Surface Mapping
Low Energy Neutrons 1977 Solar Minimum
from Space Ionizing Radiation Environment and
Shielding Tools (SIREST) web site
http//sirest.larc.nasa.gov
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Mars Surface Environment
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Model for Mars Atmosphere

• Atmospheric chemical and isotopic composition
  modeled using results from in-situ Viking 1 2
  Landers measurements for both major and minor
  components

CO2 95.32
N2 02.70 Ar
01.60 O2 00.13
CO 00.08

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Model for Mars Surface

• The surface altitude, or better the atmospheric
  depth for incoming particles, determined using a
  model for the Martian topography based on the
  data provided by the Mars Orbiter Laser Altimeter
  (MOLA) instrument on board the Mars Global
  Surveyor (MGS) spacecraft.
• The Mars surface chemical composition model based
  on an averaging process over the measurements
  obtained from orbiting spacecraft, namely the
  Mars 5 with gamma-ray spectroscopy, and from
  landers at the various landing sites, namely
  Viking Lander 1, Viling Lander 2, Phobos 2 and
  Mars Pathfinder missions.

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Model for Mars Surface

• The adopted Mars surface chemical composition

SiO2 44.2
Fe2O3 16.8 Al2O3
08.8 CaO 06.6 MgO
06.2 SO3
05.5 Na2O 02.5 TiO2
01.0
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Model for Mars Surface

• The composition, different with respect to the
  regolith (e.g. CO2 ice, H2O ice), of seasonal and
  perennial polar caps has been taken into account
  by modeling the deposition of the possible
  volatile inventory over the residual caps, along
  with its geographical variations all throughout
  the Martian year, for both the Mars North Pole
  and South Pole, from results from imaging data of
  orbiter spacecraft and from groundbased
  observations
• No 3D time dependent models for the Martians
  polar caps was previously available for radiation
  studies

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Conclusions

• The Martian surface environment including albedo
  neutrons can be calculated using existing
  transport codes
• These codes must be validated with detector
  data!!!!!!