Signatures of ground water from maps of neutron leakage flux measured by HEND Workshop
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Transcript of 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
Russian Aviation and Space AgencyInstitute for Space Research
NASA 2001 Mars Odyssey page 2
Workshop Workshop HENDHEND -- 20022002
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
Russian Aviation and Space AgencyInstitute for Space Research
NASA 2001 Mars Odyssey page 3
Workshop Workshop HENDHEND -- 20022002
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
Russian Aviation and Space AgencyInstitute for Space Research
NASA 2001 Mars Odyssey page 4
Workshop Workshop HENDHEND -- 20022002
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
Russian Aviation and Space AgencyInstitute for Space Research
NASA 2001 Mars Odyssey page 5
Workshop Workshop HENDHEND -- 20022002
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
Russian Aviation and Space AgencyInstitute for Space Research
NASA 2001 Mars Odyssey page 6
Workshop Workshop HENDHEND -- 20022002
Neutrons [0.4 eV – 100 keV]Neutrons [0.4 eV – 1 keV]
OBSERVATIONS: 45 days mapping of Mars
Russian Aviation and Space AgencyInstitute for Space Research
NASA 2001 Mars Odyssey page 7
Workshop Workshop HENDHEND -- 20022002
Neutrons [10 eV – 1 MeV] Neutrons [850 keV – 15 MeV]
OBSERVATIONS: 45 days mapping of Mars
Russian Aviation and Space AgencyInstitute for Space Research
NASA 2001 Mars Odyssey page 8
Workshop Workshop HENDHEND -- 20022002
COMPARISON: HEND and NS
Epithermal neutrons registered by NS Epithermal neutrons registered by HEND
Russian Aviation and Space AgencyInstitute for Space Research
NASA 2001 Mars Odyssey page 9
Workshop Workshop HENDHEND -- 20022002
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.
Russian Aviation and Space AgencyInstitute for Space Research
NASA 2001 Mars Odyssey page 10
Workshop Workshop HENDHEND -- 20022002
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
Russian Aviation and Space AgencyInstitute for Space Research
NASA 2001 Mars Odyssey page 11
Workshop Workshop HENDHEND -- 20022002
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.
Russian Aviation and Space AgencyInstitute for Space Research
NASA 2001 Mars Odyssey page 12
Workshop Workshop HENDHEND -- 20022002
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.