Page 1 HEND science after 9 years in space. page 2 HEND/2001 Mars Odyssey HEND ( High Energy Neutron...

HEND science after 9 years in space

HEND/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.

HEND/2001 Mars OdysseyHEND/2001 Mars Odyssey

Gamma SensorGamma Sensor

HENDHEND

2001 Mars Odyssey2001 Mars Odyssey

NSNS

HEND Instrument Status

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

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

Global Mapping of Mars neutron flux in different energy ranges

&

Global Mapping of water distribution in Martian subsurface down to depth 1 m

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

Neu

tron

Ene

rgy

SD sensor

LD sensor

Stilben

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)

Depth (cm)

Water (%)

40N

40N

Results: North high latitudes

Ice depth and water content distributions

Depth (cm)

Water (%)

Results: South high latitudes

Ice depth and water content distributions

40S

40S

Observation of Mars seasonal caps

North South

Summer

Winter

Condensation of atmospheric CO2 on Mars polar and near

polar regions

80N-90N80N-90N

SpringSpring SummerSummer FallFall WinterWinter

North Hemisphere

70N-80N70N-80N


80N-90N80N-90N

North Hemisphere

60N-70N60N-70N


70N-80N70N-80N

80N-90N80N-90N

North Hemisphere

50N-60N50N-60N


60N-70N60N-70N

70N-80N70N-80N

80N-90N80N-90N

North Hemisphere

80S-90S80S-90S

FallFall WinterWinter SpringSpring SummerSummer

Southern Hemisphere


50S-60S50S-60S70S-80S70S-80S

80S-90S80S-90S

Southern Hemisphere


50S-60S50S-60S

60S-70S60S-70S

70S-80S70S-80S

80S-90S80S-90S

Southern Hemisphere

50S-60S50S-60S


50S-60S50S-60S

60S-70S60S-70S

70S-80S70S-80S

80S-90S80S-90S

Southern Hemisphere

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

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

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

Inter-annual variations of Northern seasonal cap (60N-90N)

Inter-annual variations of Southern seasonal cap (60S-90S)

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

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

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

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.

Mass of northern seasonal cap (60N-90N)Mass of northern seasonal cap (60N-90N)

Mass of southern seasonal cap (60S-90S)Mass of southern seasonal cap (60S-90S)

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

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