Martian neutron leakage spectra

Journal Article · Fri Jun 10 00:00:00 EDT 1988 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB093iB06p06353· OSTI ID:7188205

Drake, D M; Feldman, W C; Jakosky, B M

Energy spectra of Martian leakage neutrons are calculated by a high-energy nucleon-meson transport code using a Monte Carlo technique and a one-dimensional diffusion accelerated neutral-particle transport code, which solves the Boltzmann equation. Four series of calculations were made to simulate (1) a uniform surface layer containing various amounts of H/sub 2/O, (2) different burial depths of a 50% H/sub 2/O layer underneath a 1% H/sub 2/O layer, (3) changing atmospheric pressure, and (4) a thick CO/sub 2/ ice sheet overlying a ''dirty'' water ice sheet. We found that all calculated spectra at energies less than about 1000 eV could be fitted by a superposition of thermal and epithermal functions having four free parameters. Two of these parameters, the thermal and epithermal amplitudes, were found to vary systematically over ranges exceeding 1 order of magnitude and to specify uniquely the configuration in each of the series. We conclude that measurements of leakage neutron spectra should allow determination of the hydrogen content of surface layers buried to depths up to about 100 g/cm/sup 2/ and determination of the thickness of a polar dry ice cap up to thicknesses of about 250 g/cm/sup 2/. Variations of these parameters were also shown to depend on the composition of the assumed surface layers through the average atomic mass and the macroscopic scattering and absorption cross sections. copyright American Geophysical Union 1988

• Research Organization: Los Alamos National Laboratory, Los Alamos, New Mexico
• OSTI ID: 7188205
• Journal Information: J. Geophys. Res.; (United States), Vol. 93:B6
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
MARS PLANET
NEUTRON SPECTRA
ATMOSPHERIC PRESSURE
BOLTZMANN EQUATION
CARBON DIOXIDE
CHARGED-PARTICLE TRANSPORT
HYDROGEN
ICE
MONTE CARLO METHOD
ONE-DIMENSIONAL CALCULATIONS
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
DIFFERENTIAL EQUATIONS
ELEMENTS
EQUATIONS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PARTIAL DIFFERENTIAL EQUATIONS
PLANETS
RADIATION TRANSPORT
SPECTRA
640107* - Astrophysics & Cosmology- Planetary Phenomena