Chris Okubo - Academia.edu (original) (raw)

Papers by Chris Okubo

International Journal of Speleology

Geophysical Research Letters, 2008

Science, 2007

Water has supposedly marked the surface of Mars and produced characteristic landforms. To underst... more Water has supposedly marked the surface of Mars and produced characteristic landforms. To understand the history of water on Mars, we take a close look at key locations with the High-Resolution Imaging Science Experiment on board the Mars Reconnaissance Orbiter, reaching fine spatial scales of 25 to 32 centimeters per pixel. Boulders ranging up to ∼2 meters in diameter are ubiquitous in the middle to high latitudes, which include deposits previously interpreted as finegrained ocean sediments or dusty snow. Bright gully deposits identify six locations with very recent activity, but these lie on steep (20° to 35°) slopes where dry mass wasting could occur. Thus, we cannot confirm the reality of ancient oceans or water in active gullies but do see evidence of fluvial modification of geologically recent mid-latitude gullies and equatorial impact craters.

Introduction: This abstract summarizes current results and planned activities from an ongoing ini... more Introduction: This abstract summarizes current results and planned activities from an ongoing initiative to construct a series of high-resolution structural and geologic maps in the east Candor Chasma region of Valles Marineris, Mars. The goal of this work is to advance current understanding of the coupled structural evolution of eastern Candor Chasma and the sedimentary deposits within it through a campaign of geologic unit and structural mapping at spatial resolutions that are at least an order of magnitude finer than has been achieved by previous studies in this part of Valles Marineris. This will be accomplished by characterizing the structure of the sedimentary deposits using digital elevation models (DEMs) derived from publicly released, stereo image pairs acquired by the High Resolution Imaging Science Experiment (HiRISE) camera. Work is progressing in two map areas on and adjacent to Nia Mensa (Fig. 1). Mapping is most mature in the northern Nia Mensa map area, and an initia...

Introduction: Clastic sedimentary deposits are well– known source regions for terrestrial undergr... more Introduction: Clastic sedimentary deposits are well– known source regions for terrestrial underground reservoirs of volatiles because of the high porosities and permeabilities of these rocks [1,2]. Faults and their surrounding damage zones play an important role in controlling the pathways along which volatiles tend to migrate within these reservoirs. This is because faults and attendant damage zones can act as either barriers [3–6] or conduits [7–9] to the movement of volatiles within the reservoir. Where exposed through erosion, fault–controlled reservoirs offer excellent opportunities to examine past tectonic, geochemical, hydrologic and biologic processes that originally occurred in the subsurface. The light-toned layered deposits on Mars show abundant evidence of diagenetic alteration that is attributed to subsurface fluid flow. These deposits are in places highly fractured. Therefore understanding the implications of brittle fracturing on fluid flow potential through these dep...

published in: Lunar and Planetary Science XXXVI, CDROM, Lunar and Planetary Institute, Houston (2... more published in: Lunar and Planetary Science XXXVI, CDROM, Lunar and Planetary Institute, Houston (2005). Lunar and Planetary Science XXXVI (2005) 1008.pdf

Introduction: High-resolution geologic and structural mapping of four key sites in west Candor Ch... more Introduction: High-resolution geologic and structural mapping of four key sites in west Candor Chasma is nearing completion, and new mapping is commencing at three sites in east Candor Chasma (Fig. 1). These high-resolution maps are constructed using digital elevation models (DEMs) and orthorectified imagery constructed from stereo HiRISE observations. The maps have been, or will be, formally published through the US Geological Survey’s Scientific Investigations Map series at 1:18,000 scale. This paper presents a synthesis of results from west Candor and introduces the three new sites in east Candor. West Candor Chasma: Mapping in west Candor Chasma focused on the separate regions of central Candor Colles, southeast and west Ceti Mensa and east Candor Sulci. The central Candor Colles map has been published [1] and the remaining three maps are currently under review. These maps focus on the stratified sedimentary deposits within the chasma – the canonical Late Hesperian to Early Amaz...

published in: Lunar and Planetary Science XXXIV, CD-ROM, Lunar and Planetary Institute, Houston (... more published in: Lunar and Planetary Science XXXIV, CD-ROM, Lunar and Planetary Institute, Houston (2003). Lunar and Planetary Science XXXIV (2003) 1283.pdf

INTRODUCTION: Tharsis-radial graben and pit crater chains (catenae) have been interpreted as the ... more INTRODUCTION: Tharsis-radial graben and pit crater chains (catenae) have been interpreted as the result of igneous dike intrusions [1,2,3], which attain lengths in excess of 2000 km from the center of the Tharsis volcano–tectonic province. Based on the assumption that these Tharsis–radial graben and pit crater chains are underlain by dikes, geodynamic models of lithospheric uplift have been proposed to account for the stress state required for Tharsis–radial dike propagation [4] and the attendant magma fluxes have been estimated [2]. In this abstract, we test the fundamental assumption that Tharsis–radial pit crater chains are underlain by igneous dikes by examining Phlegethon, Acheron and Tractus Catenae on the southeast flank of Alba Patera. Following [5] we compare MOLA–based topography against standard numerical model predictions of surface deformation above buried and surface– breaking dikes and normal faults. We find that these pit crater chains have local cross–strike topogra...

Introduction: Magnitudes of shear displacement along normal and thrust faults on Mercury and Mars... more Introduction: Magnitudes of shear displacement along normal and thrust faults on Mercury and Mars are characteristically smaller relative to their length, compared to the displacement to length ratios of faults on Earth (Fig. 1) [1]. Displacement to length ratios are typically 6 x 10 or 6.7 x 10 for faults on Mars [2,3] and 6.5 x 10 for faults on Mercury [Watters et al., 2000]. On Earth, this ratio is typically 2–5 x 10 over a range of tectonic settings and rock types [4–8]. Faults on Mercury and Mars thus have less displacement relative to their length than faults on Earth. Under–displacement of fractures (faults and joints) on Mercury and Mars is attributed to these planets’ smaller gravitational accelerations relative to Earth [1]. Fracture displacements may be either shear for faults or dilation for joints. The ratio of a fracture’s displacement to its length is a function of the deformation modulus of the surrounding rock mass, the yield strength of the rock near the fracture t...

Current studies of wrinkle ridge development suggest that wrinkle ridges are the surface expressi... more Current studies of wrinkle ridge development suggest that wrinkle ridges are the surface expressions of thrust folds. Specifically, wrinkle ridges may develop in a manner similar to terrestrial blind thrust anticlines [1]. The mechanical models presented here show that the width of the blind thrust anticline is dependent on fault dip and height, and that anticline height is sensitive to the slip magnitude and fault depth. These models can be used to extract subjacent fault and lithologic information from wrinkle ridge topography.

Geophysical Monograph Series, 2000

Résumé/Abstract Direct satellite data reception at high temporal frequencies and automated proces... more Résumé/Abstract Direct satellite data reception at high temporal frequencies and automated processing enable near-real-time, near-continuous thermal monitoring of volcanoes. We review what has been achieved in terms of turning this capability into real-time tools of use ...

HiRISE DTMs are produced at 1 m/px and 2 m/px, depending on source image mode. The procedure used... more HiRISE DTMs are produced at 1 m/px and 2 m/px, depending on source image mode. The procedure used to create the DTMs and their associated orthoimages is described here, as well as the products being made available via the PDS starting in 2010.

Lpi Contributions, Jul 1, 2007

The strength and deformability of light-toned layered deposits are estimated based on measurement... more The strength and deformability of light-toned layered deposits are estimated based on measurements of porosity from Microscopic Imager data acquired by MER Opportunity during its traverse from Eagle Crater to Erebus Crater.

We present an inventory of geomorphic analogues for Lake Bonneville and Mars, with focus on poten... more We present an inventory of geomorphic analogues for Lake Bonneville and Mars, with focus on potential standing-water features. The goal is to understand water as a geomorphic agent at a variety of temporal and spatial scales.

Lpi Contributions, Jul 1, 2007

The Jurassic Navajo Sandstone contains multiple features similar to the sedimentary record on Mar... more The Jurassic Navajo Sandstone contains multiple features similar to the sedimentary record on Mars. Terrestrial analogs provide key constraints and a comparative framework for remotely interpreting martian properties, processes, and history.

Faults on smaller planets and satellites than Earth have less offset D per unit length L, resulti... more Faults on smaller planets and satellites than Earth have less offset D per unit length L, resulting in smaller D/L ratios. This systematic reduction is real and results from gravity scaling of the faulting process. Quantitative scaling predictions closely match the observations.

Lunar and Planetary Science Conference, 2008

HiRISE images reveal numerous positive relief knobs amidst layered deposits in West Candor Chasma... more HiRISE images reveal numerous positive relief knobs amidst layered deposits in West Candor Chasma. We document knob characteristics and present possible origins utilizing Earth analogs. The knobs may hold records of Mars past global water cycle.

International Journal of Speleology

Geophysical Research Letters, 2008

Science, 2007

Water has supposedly marked the surface of Mars and produced characteristic landforms. To underst... more Water has supposedly marked the surface of Mars and produced characteristic landforms. To understand the history of water on Mars, we take a close look at key locations with the High-Resolution Imaging Science Experiment on board the Mars Reconnaissance Orbiter, reaching fine spatial scales of 25 to 32 centimeters per pixel. Boulders ranging up to ∼2 meters in diameter are ubiquitous in the middle to high latitudes, which include deposits previously interpreted as finegrained ocean sediments or dusty snow. Bright gully deposits identify six locations with very recent activity, but these lie on steep (20° to 35°) slopes where dry mass wasting could occur. Thus, we cannot confirm the reality of ancient oceans or water in active gullies but do see evidence of fluvial modification of geologically recent mid-latitude gullies and equatorial impact craters.

Introduction: This abstract summarizes current results and planned activities from an ongoing ini... more Introduction: This abstract summarizes current results and planned activities from an ongoing initiative to construct a series of high-resolution structural and geologic maps in the east Candor Chasma region of Valles Marineris, Mars. The goal of this work is to advance current understanding of the coupled structural evolution of eastern Candor Chasma and the sedimentary deposits within it through a campaign of geologic unit and structural mapping at spatial resolutions that are at least an order of magnitude finer than has been achieved by previous studies in this part of Valles Marineris. This will be accomplished by characterizing the structure of the sedimentary deposits using digital elevation models (DEMs) derived from publicly released, stereo image pairs acquired by the High Resolution Imaging Science Experiment (HiRISE) camera. Work is progressing in two map areas on and adjacent to Nia Mensa (Fig. 1). Mapping is most mature in the northern Nia Mensa map area, and an initia...

Introduction: Clastic sedimentary deposits are well– known source regions for terrestrial undergr... more Introduction: Clastic sedimentary deposits are well– known source regions for terrestrial underground reservoirs of volatiles because of the high porosities and permeabilities of these rocks [1,2]. Faults and their surrounding damage zones play an important role in controlling the pathways along which volatiles tend to migrate within these reservoirs. This is because faults and attendant damage zones can act as either barriers [3–6] or conduits [7–9] to the movement of volatiles within the reservoir. Where exposed through erosion, fault–controlled reservoirs offer excellent opportunities to examine past tectonic, geochemical, hydrologic and biologic processes that originally occurred in the subsurface. The light-toned layered deposits on Mars show abundant evidence of diagenetic alteration that is attributed to subsurface fluid flow. These deposits are in places highly fractured. Therefore understanding the implications of brittle fracturing on fluid flow potential through these dep...

published in: Lunar and Planetary Science XXXVI, CDROM, Lunar and Planetary Institute, Houston (2... more published in: Lunar and Planetary Science XXXVI, CDROM, Lunar and Planetary Institute, Houston (2005). Lunar and Planetary Science XXXVI (2005) 1008.pdf

Introduction: High-resolution geologic and structural mapping of four key sites in west Candor Ch... more Introduction: High-resolution geologic and structural mapping of four key sites in west Candor Chasma is nearing completion, and new mapping is commencing at three sites in east Candor Chasma (Fig. 1). These high-resolution maps are constructed using digital elevation models (DEMs) and orthorectified imagery constructed from stereo HiRISE observations. The maps have been, or will be, formally published through the US Geological Survey’s Scientific Investigations Map series at 1:18,000 scale. This paper presents a synthesis of results from west Candor and introduces the three new sites in east Candor. West Candor Chasma: Mapping in west Candor Chasma focused on the separate regions of central Candor Colles, southeast and west Ceti Mensa and east Candor Sulci. The central Candor Colles map has been published [1] and the remaining three maps are currently under review. These maps focus on the stratified sedimentary deposits within the chasma – the canonical Late Hesperian to Early Amaz...

published in: Lunar and Planetary Science XXXIV, CD-ROM, Lunar and Planetary Institute, Houston (... more published in: Lunar and Planetary Science XXXIV, CD-ROM, Lunar and Planetary Institute, Houston (2003). Lunar and Planetary Science XXXIV (2003) 1283.pdf

INTRODUCTION: Tharsis-radial graben and pit crater chains (catenae) have been interpreted as the ... more INTRODUCTION: Tharsis-radial graben and pit crater chains (catenae) have been interpreted as the result of igneous dike intrusions [1,2,3], which attain lengths in excess of 2000 km from the center of the Tharsis volcano–tectonic province. Based on the assumption that these Tharsis–radial graben and pit crater chains are underlain by dikes, geodynamic models of lithospheric uplift have been proposed to account for the stress state required for Tharsis–radial dike propagation [4] and the attendant magma fluxes have been estimated [2]. In this abstract, we test the fundamental assumption that Tharsis–radial pit crater chains are underlain by igneous dikes by examining Phlegethon, Acheron and Tractus Catenae on the southeast flank of Alba Patera. Following [5] we compare MOLA–based topography against standard numerical model predictions of surface deformation above buried and surface– breaking dikes and normal faults. We find that these pit crater chains have local cross–strike topogra...

Introduction: Magnitudes of shear displacement along normal and thrust faults on Mercury and Mars... more Introduction: Magnitudes of shear displacement along normal and thrust faults on Mercury and Mars are characteristically smaller relative to their length, compared to the displacement to length ratios of faults on Earth (Fig. 1) [1]. Displacement to length ratios are typically 6 x 10 or 6.7 x 10 for faults on Mars [2,3] and 6.5 x 10 for faults on Mercury [Watters et al., 2000]. On Earth, this ratio is typically 2–5 x 10 over a range of tectonic settings and rock types [4–8]. Faults on Mercury and Mars thus have less displacement relative to their length than faults on Earth. Under–displacement of fractures (faults and joints) on Mercury and Mars is attributed to these planets’ smaller gravitational accelerations relative to Earth [1]. Fracture displacements may be either shear for faults or dilation for joints. The ratio of a fracture’s displacement to its length is a function of the deformation modulus of the surrounding rock mass, the yield strength of the rock near the fracture t...

Current studies of wrinkle ridge development suggest that wrinkle ridges are the surface expressi... more Current studies of wrinkle ridge development suggest that wrinkle ridges are the surface expressions of thrust folds. Specifically, wrinkle ridges may develop in a manner similar to terrestrial blind thrust anticlines [1]. The mechanical models presented here show that the width of the blind thrust anticline is dependent on fault dip and height, and that anticline height is sensitive to the slip magnitude and fault depth. These models can be used to extract subjacent fault and lithologic information from wrinkle ridge topography.

Geophysical Monograph Series, 2000

Résumé/Abstract Direct satellite data reception at high temporal frequencies and automated proces... more Résumé/Abstract Direct satellite data reception at high temporal frequencies and automated processing enable near-real-time, near-continuous thermal monitoring of volcanoes. We review what has been achieved in terms of turning this capability into real-time tools of use ...

HiRISE DTMs are produced at 1 m/px and 2 m/px, depending on source image mode. The procedure used... more HiRISE DTMs are produced at 1 m/px and 2 m/px, depending on source image mode. The procedure used to create the DTMs and their associated orthoimages is described here, as well as the products being made available via the PDS starting in 2010.

Lpi Contributions, Jul 1, 2007

The strength and deformability of light-toned layered deposits are estimated based on measurement... more The strength and deformability of light-toned layered deposits are estimated based on measurements of porosity from Microscopic Imager data acquired by MER Opportunity during its traverse from Eagle Crater to Erebus Crater.

We present an inventory of geomorphic analogues for Lake Bonneville and Mars, with focus on poten... more We present an inventory of geomorphic analogues for Lake Bonneville and Mars, with focus on potential standing-water features. The goal is to understand water as a geomorphic agent at a variety of temporal and spatial scales.

Lpi Contributions, Jul 1, 2007

The Jurassic Navajo Sandstone contains multiple features similar to the sedimentary record on Mar... more The Jurassic Navajo Sandstone contains multiple features similar to the sedimentary record on Mars. Terrestrial analogs provide key constraints and a comparative framework for remotely interpreting martian properties, processes, and history.

Faults on smaller planets and satellites than Earth have less offset D per unit length L, resulti... more Faults on smaller planets and satellites than Earth have less offset D per unit length L, resulting in smaller D/L ratios. This systematic reduction is real and results from gravity scaling of the faulting process. Quantitative scaling predictions closely match the observations.

Lunar and Planetary Science Conference, 2008

HiRISE images reveal numerous positive relief knobs amidst layered deposits in West Candor Chasma... more HiRISE images reveal numerous positive relief knobs amidst layered deposits in West Candor Chasma. We document knob characteristics and present possible origins utilizing Earth analogs. The knobs may hold records of Mars past global water cycle.