Effects of Impact and Heating on the Properties of Clays on Mars Patricia Gavin V. Chevrier, K. Ninagawa, S. Hasegawa

Introduction Clays surrounded by lava flows and in crater ejecta Clays surrounded by lava flows and in crater ejecta Heat and shock effects Possible effects on clays Possible effects on clays Loss of water Structural change New phases formed Experiments Experiments Heat in oven Impact in light gas gun Poulet et al., 2005 Mangold et al., 2007

Heating experiments 2 relevant clays 2 relevant clays Montmorillonite (Ca, Al clay) Montmorillonite (Ca, Al clay) Nontronite (Fe 3+ clay) Nontronite (Fe 3+ clay) Thermal treatment in tube oven Thermal treatment in tube oven 350 o C < T < 1150 o C 350 o C < T < 1150 o C 4 hr < t < 24 hr 4 hr < t < 24 hr Air and CO 2 atmosphere Air and CO 2 atmosphere Analysis Analysis XRD XRD ESEM ESEM Reflectance spectra Reflectance spectra

Color Changes Nontronite UntreatedHeated Montmorillonite

Nontronite: Low temperature T < 750 o C: Loss of interlayer peak T < 750 o C: Loss of interlayer peak Collapse of structure Collapse of structure Loss of water Loss of water ~25% mass Untreated Air, T = 630 o C CO 2, T = 475 o C Counts/sec

Nontronite: Low Temperature Untreated T = 475 o C T = 630 o C OH bandWater band Metal - OH band

Nontronite: Intermediate Temperature 800 < T < 1000 o C: complex mixture of secondary phases 800 < T < 1000 o C: complex mixture of secondary phases Large peaks = nanocrystalline phases Large peaks = nanocrystalline phases Solid-solid transformation Solid-solid transformation no melting no melting Counts/sec Offset by 100 units

Nontronite: High temperature Counts/sec T > 1100 o C: melting and crystallization of high temperature phases sillimanite hematite cristobalite glass

Nontronite: Intermediate and High Temperature Untreated T = 1130 o C T = 975 o C T = 810 o C

Montmorillonite: Low Temperature T < 750 o C: most peaks still intact T < 750 o C: most peaks still intact More resistant to thermal alteration More resistant to thermal alteration Quartz Quartz Albite Albite Untreated T = 630 o C Offset by 400 units Counts/sec

Montmorillonite: High Temperature T > 1100 o C: formation of high temperature phases T > 1100 o C: formation of high temperature phases silimanite silimanite cristobalite cristobalite mica mica amorphous glass amorphous glass Counts/sec

Montmorillonite heated in Air T = 1130 o C T = 630 o C T = 880 o C Untreated

Impact Experiments Same clays Same clays Montmorillonite (Ca, Al clay) Montmorillonite (Ca, Al clay) Nontronite (Fe 3+ clay) Nontronite (Fe 3+ clay) Impact with light gas gun Impact with light gas gun Velocity km/s Velocity km/s SUS projectile SUS projectile Analysis Analysis XRD XRD Reflectance spectra Reflectance spectra Autodyne software Autodyne software Max pressure and temperature Max pressure and temperature

Impacted nontronite No real change No real change All peaks still visible All peaks still visible Interlayer peak intact Interlayer peak intact Peak intensity decrease Peak intensity decrease Counts/sec v = 2.47km/s v = 3.27km/s Offset by 400 units

Impacted Nontronite Untreated v = 2.5 km/s v = 2.07 km/s v = 2.15 km/s v = 3.27 km/s

Shock Wave Propagation Modeling v = 2.47km/s 10ms time step

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Shock Wave Propagation Modeling v = 2.47km/s

Impacted Montmorillonite Untreated v = 2.5 km/s

Clays in Craters on Mars Mangold, et al., 2007

Clays in Craters on Mars T = 630 o C T = 475 o C

Magnetic Properties T < 600 o C: paramagnetic Fe 3+ T < 600 o C: paramagnetic Fe 3+ T > 1000 o C: T > 1000 o C: Low saturation magnetization Low saturation magnetization High remanent magnetization High remanent magnetization High coercitive field High coercitive field Similar to hematite Similar to hematite Applied Field (T) Magnetization (Am 2 /kg)

Magnetic Properties 800 o C < T < 1000 o C: Wasp- waisted 800 o C < T < 1000 o C: Wasp- waisted Two or more components present Two or more components present Multidomain and paramagnetic particles Multidomain and paramagnetic particles Maghemite? Maghemite? Applied Field (T) Magnetization (Am 2 /kg) Applied Field (T) 5.1 A

Conclusions No distinctive effect of CO 2 on clay transformations No distinctive effect of CO 2 on clay transformations Heating: intense effect on clays Heating: intense effect on clays Loss of water at relatively low temperatures Loss of water at relatively low temperatures Melting and recrystallization at high temperatures Melting and recrystallization at high temperatures Disappearance of bands in FTIR Disappearance of bands in FTIR Impact affects smectites Impact affects smectites Decrease in band depth (impact glass?) Decrease in band depth (impact glass?) Magnetic properties Magnetic properties Possible new phase at intermediate temperatures Possible new phase at intermediate temperatures Non-stiochiometric phase Non-stiochiometric phase

Implications for Mars Clays detected in small crater ejecta were pre-existing Clays detected in small crater ejecta were pre-existing Different spectral features from untreated samples Different spectral features from untreated samples Large impacts may generate enough heat to induce transformations Large impacts may generate enough heat to induce transformations Contact with lava flows should strongly affect clays Contact with lava flows should strongly affect clays Heated nontronite may explain origin and magnetic properties of red dust Heated nontronite may explain origin and magnetic properties of red dust Hematite (superparamagnetic phase) Hematite (superparamagnetic phase) Maghemite Maghemite