signatures of ground water from maps of neutron leakage flux measured by hend workshop

Russian Aviation and Space AgencyInstitute for Space Research

NASA 2001 Mars Odyssey page 1

Workshop Workshop HENDHEND -- 20022002

Signatures of ground water from Signatures of ground water from maps of neutron leakage flux maps of neutron leakage flux

measured by HENDmeasured by HEND

WorkshopWorkshop““The First year of HEND operations on the NASA Odyssey Mars The First year of HEND operations on the NASA Odyssey Mars

Orbiter”Orbiter”

Moscow, RussiaMay 20-22, 2002




M.Litvak, D.Anfimov, A.Kozyrev, I. Mitrofanov and A.Sanin (1

W.Boynton, D.Hamara and C.Shinohara (2

R.S.Saunders (3

1) Institute for Space Research, Moscow, Russia

2) University of Arizona, Tucson, USA

3) JPL, Pasadena, USA




Galactic Cosmic Rays freely propagates through thin Martian atmosphere and produce neutrons, gamma-rays and X-rays in the 2-3 meters subsurface layer

Their flux and energy spectra manifest the elementary composition of the “red planet” subsurface




HEND was designed for detection of high

energy neutrons from the Martian

surface

HEND has three detectors of neutrons based on proportional counters 3He with thick (LD), medium (MD) and thin (SD) moderators, one scintillation detector for fast neutrons IN/SC

and detector for anti-coincidence OUT/SC




Sensitivity and Energy Ranges of

HEND Detectors:

LD: 10.0 eV - 1.0 MeV

MD: 0.4 eV -100.0 keV

SD: 0.4 eV - 1.0 keV

IN/SC/N: 850 keV – 15,0 MeV

IN/SC/G: 60 keV – 2.0 MeV

OUT/SC: 30 keV – 1.0 MeV




Neutrons [0.4 eV – 100 keV]Neutrons [0.4 eV – 1 keV]

OBSERVATIONS: 45 days mapping of Mars




Neutrons [10 eV – 1 MeV] Neutrons [850 keV – 15 MeV]

OBSERVATIONS: 45 days mapping of Mars




COMPARISON: HEND and NS

Epithermal neutrons registered by NS Epithermal neutrons registered by HEND




RELIABILITY OF MEASUREMENTS

Epithertmal neutrons

All proportional counters maps demonstrate the similar features.

All maps features are reproduced for different periods of measurements.

There is good correspondence between HEND epithermal neutrons maps and NS epithermal neutron map.

Fast neutrons

The map created for Stilben detector demonstrates the similar features on South and around Tharsis Montes region as seen in proportional counters.

All map features are reproduced for different periods of measurements.




Epithermal neutrons Epithermal neutrons

The maximal counts rate is observed The maximal counts rate is observed South-East from Tharsis Montes in the South-East from Tharsis Montes in the region around the point with coordinates region around the point with coordinates (270°, -30°). (270°, -30°).

A huge depression is detected above the very large province at the Southern hemisphere with area Seth

(S) ≈ 9.7·ּ106km2

(South of -60° latitude).

Another depression, but with much smaller area Seth

(N) ≈ 5·106 km2 is observed

in the Northern hemisphere to the North from Alba Patera around the point with coordinates (240°, +60°)

The lagest deficit in neutron flux is equal 10 times

FEMENOLOGIAL RESULTS

Fast neutrons Fast neutrons

The maximal counts rate is observed The maximal counts rate is observed South-East from Tharsis Montes in the South-East from Tharsis Montes in the region around the point with coordinates region around the point with coordinates (270°, -30°). (270°, -30°).

A significant depression is detected above the small province at the Southern hemisphere with area Seth

(S) ≈ 2.5·ּ106 km2

(South of -60° latitude).

A significant depression, but with much larger area Seth

(N) ≈ ּ107 km2 is observed

above the Northern hemisphere

The largest deficit in neutron flux is equal 3.3 times




COMPARISON WITH EARTH MOON

The maximal deficit The maximal deficit of neutron flux seen of neutron flux seen on the Moon is less on the Moon is less then 1.5 times.then 1.5 times.In case of Mars this In case of Mars this value may reach 10 value may reach 10 times. times.




MODEL INTERPRETATIONS

South poleSouth pole

Comparison of two deficits (3.3 Comparison of two deficits (3.3 and 10 times) of fast and and 10 times) of fast and epithermal neutron fluxes may be epithermal neutron fluxes may be explained as following:explained as following:

We see layered subsurface which We see layered subsurface which consists of layer of water ice consists of layer of water ice positioned in the subsurface positioned in the subsurface below a dry layer of SObelow a dry layer of SO

22 with the with the

thickness ~70 cmthickness ~70 cm

North poleNorth pole

The deficit of fast neutron flux and The deficit of fast neutron flux and the absence of significant deficit of the absence of significant deficit of epithermal neutron flux above North epithermal neutron flux above North pole may be explained as following:pole may be explained as following:

We see homogeneous subsurface We see homogeneous subsurface layer which contains about layer which contains about 55 percent percent of water. of water.

signatures of ground water from maps of neutron leakage flux measured by hend workshop

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