Study of bound water in the surface layer of Mars Workshop HEND-2002 “The First year of HEND operations on the NASA Odyssey Mars Orbiter” May 20-22, 2002 Institute for Space Research Moscow, Russia Vernadsky Institute of Geochemistry and Analytical Chemistry Russian Acedemy of Science Moscow Russia Alexander T. Basilevsky

Bound water - water incorporated into minerals and rocks which can not be removed without changing structure or composition of these materials. Minerals H2O content Gypsum - CaSO 4 2H 2 O 21% Goethite - FeO (OH) 10% Nontronite - Na 0.33 Fe 2 3+ (Al 0.33 Si 3.67 )O 10 (OH) 2 nH 2 O 5-15% Chlorite - (Mg,Fe 2+, Fe 3+ ) 6 AlSi 3 O 10 (OH) % Serpentine - (MgFe) 3 Si 2 O 5 (OH) % Hornblende - (Ca,Na) 2-3 (Mg,Fe 2+,Fe 3+,Al) 5 (Al,Si) 8 (OH) 2 2-3% Rocks Basalt - volcanic rock with 44-50% SiO to 2% Andesite - volcanic rock with 53-63% SiO 2 1-4% Rhyolite - volcanic rock with >68% SiO 2 3-7% Clays of platforms of Earth 4-6% Martian soil (Viking GS-MS estimate) up to 1%

Bound water in tholeitic basalts of intra-plate hot spots, Earth

Water on Mars: Noachian Period -Warm and wet or cold and dry? If it was water, it should be chemically incorporated into weathering products and sediments and its hydrogen may potentially be seen in HEND data Viking image of cratered terrain with valley network

Water on Mars: Hesperian Period - Outflow channels - water or liquid CO 2 If it was water, their deposits may contain H 2 O-OH-bearing minerals and their hydrogen may potentially be seen in HEND data Viking image of Mars Pathfinder site at the mouth of Ares Vallis

Water on Mars: Hesperian Period - Did aqueous ocean exist on Mars? If yes, its sediments should contain H 2 O-OH-bearing minerals and their hydrogen may potentially be seen in HEND data Mola topography map of Mars. Courtesy of Mola Team

Water on Mars: Amazonian Period Was liquid water on and near the surface? If yes, surface deposits may contain H 2 O-OH-bearing minerals and their hydrogen may potentially be seen in HEND data MOC image of gullies on the walls of crater Kaiser (46.5S, 341.4W).

Impact-induced and magmatic hydrothermal activity Amount of impact-induced and magmatic hydrothermal mineralization decreases with depth ( Masaitis & Naumov, 1993 ). Should be most prominent on the surface. Possible (magmatic) analog: Hydrothermal deposits of Yellowstone National Park Bedrock: Rhyolite ( Bauer, 1948; Browny, 1978 ) Hydrothermal deposits: Travertine CaCO 3, Geiserite SiO 2 High-silica zeolites, Clays… Courtesy of Elizabeth Tritthart, West Yellowstone Web Works Mammoth TerraceNorris Geiser

How to search for bound water? - To study areas where seasonal/perrenial ices/frosts are not expected: Equatorial zone for all seasons and mid-latitudes at summer Mola shaded relief map of Mars. Courtesy of MOLA Team

General approach: - To correlate HEND data with a) bedrock geology b) topography and c) surface roughness Geologic map of Mars. Tanaka et al., 1978 a)

General approach: - To correlate HEND data with a) bedrock geology b) topography and c) surface roughness Mola topography map of Mars. Courtesy of MOLA Team b)

Map of kilometer roughness of Mars. Kreslavsky and Head, 2000 General approach: - To correlate HEND data with a) bedrock geology b) topography and c) surface roughness c)

HEND data: (0.4 eV-100 keV)

HEND v.s. bedrock geology

HEND v.s. MOLA topography

HEND v.s. MOLA km-scale roughness

Discussion and conclusions Some correlation of HEND measured neutron flux with geologic structures of Mars is seen: Syrtis Major Planitia (more H, hyps. higher) v.s Isidis Planitia (less H, hyps. lower) Hellas basin floor (more H, hyps. lower) v.s. Argyre basin floor (less H, hyps higher) Noachian-Hesperian cratered terrain within 0-40W, 30N-15S has highest contents of H among all equatorial zone, being usual in hypsometry and surface roughness Medusa Fossae: increase in H content comparing to surrounding areas Elysium Fossae: increase in H content comparing to Elysium Mons and its other surroundings Olympus, Arsia, Pavonis, Ascreus volcanic constructs show low H contents, same as materials of close vicinities More analysis needed to reach meaningful conclusions

HEND data: (0.4 eV-100 keV) HEND data: (1-7 MeV)

Needs for future studies To understand meaning of neutron flux of different energies in the geological context (likbez) To have HEND results maps in cylindical projection To work on different gradations of the flux intensity categories on the maps To play with degree of smoothening on the maps Calibration of the results in percent of H 2 O Possibility of improvement of spatial resolution due to multiple overlapping of the measuring orbits?