1. page 1 HEND science after 9 years in space

2. page 2 HEND/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.

3. page 3 HEND/2001 Mars Odyssey

4. page 4 HEND Instrument Status

5. 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

6. 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

7. 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

8. page 8 NorthSouth Summer Epithermal neutron flux map averaged over 8 years of orbit observations Ten times drop off of neutron flux showed presence of water ice

9. page 9 Neutron Energy SD sensor LD sensor Stilben

10. page 10 10 Testing model & MCNPX code =  (C ik – M ik ) 2  ik 2 22 (C ik,  ik 2 ) (M ik ) Different detectors Model Testing Machine Where k - index of given pixel on map, C ik – 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, M ik – 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)

11. page 11 Depth (cm) Water (%) 40N Results: North high latitudes Ice depth and water content distributions

12. page 12 Depth (cm) Water (%) Results: South high latitudes Ice depth and water content distributions 40S

13. page 13 Observation of Mars seasonal caps

14. page 14 NorthSouth Summer Winter Condensation of atmospheric CO 2 on Mars polar and near polar regions

15. page 15 80N-90N SpringSummerFallWinter North Hemisphere

16. page 16 70N-80N SpringSummerFallWinter 80N-90N North Hemisphere

17. page 17 60N-70N SpringSummerFallWinter 70N-80N 80N-90N North Hemisphere

18. page 18 50N-60N SpringSummerFallWinter 60N-70N 70N-80N 80N-90N North Hemisphere

19. page 19 80S-90S FallWinterSpringSummer Southern Hemisphere

20. page 20 FallWinterSpringSummer 50S-60S 70S-80S 80S-90S Southern Hemisphere

21. page 21 FallWinterSpringSummer 50S-60S 60S-70S 70S-80S 80S-90S Southern Hemisphere

22. page 22 50S-60S FallWinterSpringSummer 50S-60S 60S-70S 70S-80S 80S-90S Southern Hemisphere

23. page 23 Polar regions of Mars. Production of neutrons in the subsurface (<1-2 m depths) Summer Subsurface depth [ < 1-2 m below the surface ] Neutron signal vs Martian seasons Martian seasons, L s Water ice rich layer Observable subsurface layer consists of water ice only

24. page 24 Dry CO 2 deposit Polar regions of Mars. Production of neutrons in the subsurface (<1-2 m depths) Water ice rich layer Fall, Winter & Spring Subsurface depth [ < 1-2 m below the surface ] Neutron signal vs Martian seasons Martian seasons, L s Observable subsurface layer consists of water ice only

25. 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

26. page 26 Inter-annual variations of Northern seasonal cap (60N-90N)

27. page 27 Inter-annual variations of Southern seasonal cap (60S-90S)

28. 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

29. page 29 80S-90S 70S-80S 60S-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

30. page 30 Estimation of volume density (g/cm 3 ) of northern seasonal cap MOLA: Max thickness ~1.2 m MOLA HEND HEND: Max column density ~40 g/cm 3 ρ  0.33 g/cm 3

31. 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.

32. page 32 Mass of northern seasonal cap (60N-90N)

33. page 33 Mass of southern seasonal cap (60S-90S)

34. 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 CO 2 deposit’s column density (g/cm 2 )  Estimation of CO 2 column density at different latitude belts.  Estimation of mass of seasonal caps  Estimation of CO 2 deposit’s volume density (g/cm 3 ) from comparison with MOLA  Comparison with other data sets  Comparison with GCM  Comparison with GRS data  Comparison with MOLA data