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Prediction of Martian Surface Neutron Environment M. S. Clowdsley 1 , G. DeAngelis 2 , J. W. Wilson 1 , F. F. Badavi 3 , and R. C. Singleterry 1 1 NASA Langley Research Center, Hampton, VA 2 Old Dominion University, Norfolk, VA 3 Christopher Newport University, Newport News, VA

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Prediction of martian surface neutron environment l.jpg

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


Radiation transport codes l.jpg
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!!!


Planetary surface material and atmosphere l.jpg

Mars Induced Fields

Planetary Surface Material and Atmosphere

GCR ion

High energy

particles

Diffuse

neutrons

(Simonsen et al.)


Gcr environments l.jpg
GCR Environments

Free Space

Martian Surface

1977 Solar Minimum (solid)

1990 Solar Maximum (dashed)



Mars surface worst case spe environment l.jpg
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



Mars surface mapping l.jpg
Mars Surface Mapping

Charged Ions – 1977 Solar Minimum

from Space Ionizing Radiation Environment and Shielding Tools (SIREST) web site

http://sirest.larc.nasa.gov


Mars surface mapping9 l.jpg
Mars Surface Mapping

Neutrons – 1977 Solar Minimum

from Space Ionizing Radiation Environment and Shielding Tools (SIREST) web site

http://sirest.larc.nasa.gov


Mars surface mapping10 l.jpg
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



Model for mars atmosphere l.jpg
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


Model for mars surface l.jpg
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.


Model for mars surface14 l.jpg
Model for Mars Surface

SiO2 % 44.2

Fe2O3 % 16.8

Al2O3 % 08.8

CaO % 06.6

MgO % 06.2

SO3 % 05.5

Na2O % 02.5

TiO2 % 01.0

  • The adopted Mars surface chemical composition:


Model for mars surface15 l.jpg
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!!!!!!


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