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page 1
HEND science after 9 years in space
page 2HEND/2001 Mars OdysseyHEND/2001 Mars Odyssey
HEND (High Energy Neutron Detector) was developed in Space Research Institute in 1996-2001 specially for NASA Mars Odyssey mission to provide global orbital mapping of Martian neutron albedo in different energy bands. It includes three proportional counters surrounded with different thickness polyethylene and organic scintillator to detect neutrons starting from 0.4 eV up to 10 MeV.
page 3HEND/2001 Mars OdysseyHEND/2001 Mars Odyssey
Gamma SensorGamma Sensor
HENDHEND
2001 Mars Odyssey2001 Mars Odyssey
NSNS
page 4
HEND Instrument Status
page 5
HEND health: HEND operates nominally in science operation mode, none of anomalies are observed, all detectors (5 for measuring neutrons, 2 for gammas) are on and in a good shape. No spectra degradation is visible in HEND detectors, spectra shape is very stable. Current examples of spectra (accumulated for Apr 2010) in proportional counters (epithermal neutrons) and in organic scintillator (fast neutrons) are presented below in comparison with spectra measured at the beginning mapping in April 2002
page 6
HEND/Mars Odyssey SCIENCE
Global Mapping of Mars neutron flux in different energy ranges Global Mapping of water distribution in Martian subsurface down to depth 1m Observation of Mars seasons Observation of Galactic cosmic rays flux variations (solar cycle) Observation of Solar Particle Events Participation in Gamma Ray Burst Interplanetary Network
page 7
Global Mapping of Mars neutron flux in different energy ranges
&
Global Mapping of water distribution in Martian subsurface down to depth 1 m
page 8
North South
SummerEpithermal
neutron flux map averaged over 8 years
of orbit observations
Ten times drop off of neutron flux showed presence of water ice
Ten times drop off of neutron flux showed presence of water ice
page 9
Neu
tron
Ene
rgy
SD sensor
LD sensor
Stilben
page 1010
Testing model&
MCNPX code
= (Cik – Mik)2
ik2
2
(Cik ,ik2) (Mik)
Different detectors
Model Testing Machine
Where k - index of given pixel on map, Cik – normalized (to Solis Planum, where we suggested presence of 2% of water by weight) counting rates in different i detectors (SD, MD, LD, Stilben), ik – statistical erorrs of counting rates, Mik – normalized (to 2% of water) modeled counting rates corresponded to the water distribution with given parameters (thickens of upper layer and water content in bottom one)
page 11
Depth (cm)
Water (%)
40N
40N
Results: North high latitudes
Ice depth and water content distributions
page 12
Depth (cm)
Water (%)
Results: South high latitudes
Ice depth and water content distributions
40S
40S
page 13
Observation of Mars seasonal caps
page 14
North South
Summer
Winter
Condensation of atmospheric CO2 on Mars polar and near
polar regions
page 15
80N-90N80N-90N
SpringSpring SummerSummer FallFall WinterWinter
North Hemisphere
page 16
70N-80N70N-80N
SpringSpring SummerSummer FallFall WinterWinter
80N-90N80N-90N
North Hemisphere
page 17
60N-70N60N-70N
SpringSpring SummerSummer FallFall WinterWinter
70N-80N70N-80N
80N-90N80N-90N
North Hemisphere
page 18
50N-60N50N-60N
SpringSpring SummerSummer FallFall WinterWinter
60N-70N60N-70N
70N-80N70N-80N
80N-90N80N-90N
North Hemisphere
page 19
80S-90S80S-90S
FallFall WinterWinter SpringSpring SummerSummer
Southern Hemisphere
page 20
FallFall WinterWinter SpringSpring SummerSummer
50S-60S50S-60S70S-80S70S-80S
80S-90S80S-90S
Southern Hemisphere
page 21
FallFall WinterWinter SpringSpring SummerSummer
50S-60S50S-60S
60S-70S60S-70S
70S-80S70S-80S
80S-90S80S-90S
Southern Hemisphere
page 22
50S-60S50S-60S
FallFall WinterWinter SpringSpring SummerSummer
50S-60S50S-60S
60S-70S60S-70S
70S-80S70S-80S
80S-90S80S-90S
Southern Hemisphere
page 23
Polar regions of Mars. Production of neutrons in the subsurface (<1-2 m depths)
Summer
Sub
surf
ace
depth
[ < 1-2 m below the surface ]
Neutr
on
sig
nal vs
Mart
ian s
easo
ns
Martian seasons, Ls
Water ice rich layer
Observable subsurface layer consists of water ice
only
page 24
Dry CO2 deposit
Polar regions of Mars. Production of neutrons in the subsurface (<1-2 m depths)
Water ice rich layer
Fall, Winter & Spring
Sub
surf
ace
depth
[ < 1-2 m below the surface ]
Neutr
on
sig
nal vs
Mart
ian s
easo
ns
Martian seasons, Ls
Observable subsurface layer consists of water ice
only
page 25
Many years on the orbit give us possibility to measure inter annual variations of Martian seasonal cycle: how it is changes on the base of four successive Martian years.
Inter annual variations
page 26
Inter-annual variations of Northern seasonal cap (60N-90N)
page 27
Inter-annual variations of Southern seasonal cap (60S-90S)
page 28
80N-90N
70N-80N
60N-70N
Different colors dots corresponds to the
different Martian years. Black solid curves
corresponds to the column density averaged through the several Martian years
Northern polar cap
page 29
80S-90S
70S-80S60S-70S
Different colors dots corresponds to the
different Martian years. Black solid curves
corresponds to the column density averaged through the several Martian years
Southern polar cap
page 30
Estimation of volume density (g/cm3) of northern seasonal cap
MOLA: Max thickness ~1.2 m
MOLA
HEND
HEND: Max column density ~40 g/cm3
ρ 0.33 g/cm3
page 31
Masses of seasonal caps
Knowing column density of CO2 deposit it is possible to go to the estimation of total masses of Martian seasonal caps. Because Mass of CO2 at given region is equal to multiplication of average column density by area of this region. Summing by latitude belts we may estimate the total mass of northern and southern seasonal cap and make comparison with predictions of General Circulation Model (NASA Ames Research Center) and other measurements taken for example from GRS/Mars Odyssey & NS/Mars Odyssey or with gravity models.
page 32
Mass of northern seasonal cap (60N-90N)Mass of northern seasonal cap (60N-90N)
page 33
Mass of southern seasonal cap (60S-90S)Mass of southern seasonal cap (60S-90S)
page 34
CONCLUSIONS
Continuous mapping of Mars neutron albedo for ~ 9 years. Detection of significant regional variations as a signature of water/water ice Observation of seasonal variations Coverage of several Martian years. Monitoring of year to year difference
Water/Water ice distribution. Detection of water ice at high latitude north and south provinces. Model depended deconvolution of data to test double layered model of regolith Mapping of water ice content and ice depth
Estimation of CO2 deposit’s column density (g/cm2) Estimation of CO2 column density at different latitude belts. Estimation of mass of seasonal caps Estimation of CO2 deposit’s volume density (g/cm3) from comparison with MOLA
Comparison with other data sets Comparison with GCM Comparison with GRS data Comparison with MOLA data