Effects of impact and heating on the properties of clays on mars
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Effects of Impact and Heating on the Properties of Clays on Mars. Patricia Gavin V. Chevrier, K. Ninagawa, S. Hasegawa. Clays surrounded by lava flows and in crater ejecta Heat and shock effects Possible effects on clays Loss of water Structural change New phases formed Experiments

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Effects of Impact and Heating on the Properties of Clays on Mars

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Effects of Impact and Heating on the Properties of Clays on Mars

Patricia Gavin

V. Chevrier, K. Ninagawa, S. Hasegawa


Clays surrounded by lava flows and in crater ejecta

Heat and shock effects

Possible effects on clays

Loss of water

Structural change

New phases formed

Experiments

Heat in oven

Impact in light gas gun

Introduction

Poulet et al., 2005 Mangold et al., 2007


Heating experiments

  • 2 relevant clays

    • Montmorillonite (Ca, Al clay)

    • Nontronite (Fe3+ clay)

  • Thermal treatment in tube oven

    • 350oC < T < 1150oC

    • 4 hr < t < 24 hr

    • Air and CO2 atmosphere

  • Analysis

    • XRD

    • ESEM

    • Reflectance spectra


Color Changes

UntreatedHeated

Nontronite

Montmorillonite


Nontronite: Low temperature

Counts/sec

Untreated

Air, T = 630oC

CO2, T = 475oC

  • T < 750oC: Loss of interlayer peak

  • Collapse of structure

  • Loss of water

    • ~25% mass


Nontronite: Low Temperature

Untreated

T = 475oC

T = 630oC

OH band

Water band

Metal - OH band


800 < T < 1000oC: complex mixture of secondary phases

Large peaks = nanocrystalline phases

Solid-solid transformation

no melting

Nontronite: Intermediate Temperature

Counts/sec

Offset by 100 units


Nontronite: High temperature

Counts/sec

  • T > 1100oC: melting and crystallization of high temperature phases

    • sillimanite

    • hematite

    • cristobalite

    • glass


Nontronite: Intermediate and High Temperature

Untreated

T = 810oC

T = 975oC

T = 1130oC


Montmorillonite: Low Temperature

Counts/sec

  • T < 750oC: most peaks still intact

  • More resistant to thermal alteration

  • Quartz

  • Albite

Untreated

T = 630oC

Offset by 400 units


Montmorillonite: High Temperature

  • T > 1100oC: formation of high temperature phases

    • silimanite

    • cristobalite

    • mica

    • amorphous glass

Counts/sec


Montmorillonite heated in Air

T = 880oC

T = 630oC

Untreated

T = 1130oC


Impact Experiments

  • Same clays

    • Montmorillonite (Ca, Al clay)

    • Nontronite (Fe3+ clay)

  • Impact with light gas gun

    • Velocity 2 - 3.3 km/s

    • SUS projectile

  • Analysis

    • XRD

    • Reflectance spectra

    • Autodyne software

      • Max pressure and temperature


Impacted nontronite

Counts/sec

  • No real change

  • All peaks still visible

  • Interlayer peak intact

  • Peak intensity decrease

v = 2.47km/s

v = 3.27km/s

Offset by 400 units


Impacted Nontronite

Untreated

v = 2.5 km/s

v = 2.15 km/s

v = 2.07 km/s

v = 3.27 km/s


Shock Wave Propagation Modeling

10ms time step

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


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 = 475oC

T = 630oC


Magnetization (Am2/kg)

Applied Field (T)

Magnetic Properties

  • T < 600oC: paramagnetic Fe3+

  • T > 1000oC:

    • Low saturation magnetization

    • High remanent magnetization

    • High coercitive field

    • Similar to hematite


Magnetization (Am2/kg)

Applied Field (T)

Magnetization (Am2/kg)

Applied Field (T)

Magnetic Properties

  • 800oC < T < 1000oC: Wasp-waisted

    • Two or more components present

    • Multidomain and paramagnetic particles

  • Maghemite?

5.1 A


Conclusions

  • No distinctive effect of CO2 on clay transformations

  • Heating: intense effect on clays

    • Loss of water at relatively low temperatures

    • Melting and recrystallization at high temperatures

    • Disappearance of bands in FTIR

  • Impact affects smectites

    • Decrease in band depth (impact glass?)

  • Magnetic properties

    • Possible new phase at intermediate temperatures

    • Non-stiochiometric phase


Implications for Mars

  • Clays detected in small crater ejecta were pre-existing

    • Different spectral features from untreated samples

    • Large impacts may generate enough heat to induce transformations

    • Contact with lava flows should strongly affect clays

  • Heated nontronite may explain origin and magnetic properties of red dust

    • Hematite (superparamagnetic phase)

    • Maghemite


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