Gaia Stucky de QuayBasins Research Group (BRG)Imperial College Londong.stucky-de-quay14@ic.ac.uk

Landslides on Mars: Evidence of ancient glaciers?

Landslides on Mars: Evidence of ancient glaciers?

Sub-surfaceVegetationSoilGroundwater

Human activityConstructionBlastingDeforestation

Active TectonicsVolcanicEarthquakesLiquefaction

Dynamic climateRivers/OceanSnow/RainErosion

10 km

2 km

Structure

Background

PART I: Building a landslide catalogue

PART II: In-depth study of small-scale failure

Introduction

Summary

Background & Literature

Introduction

Sharp, 1973 (Mariner 9)

Google Earth (CTX)

Valles Marineris(4000 km long)

Grand canyon 18 miles wide, 1 mile deep

Blocky/hummock

y

Longitudinal ridges

Massive runout/volume

WET

DRYvs.

Emplacement?

Comparison to terrestrial processes

Sherman Landslide, Alaska(1966)

Morphology?

Sliding on a cushion of steamLubricated by debris/air Dispersive grain flow

Bulk fluidizationBasal lubrication

Ground iceSurface iceSubaqueous (lacustrine)Groundwater

Melting ice lenses Debris flowOrigin?

Marsquakes & increased shear stresses

PART I: Building a landslide catalogue1. Past and current catalogues (10-103)

2. Data and methodology

1. Program: ArcGIS + Google Earth2. Data: CTX (5m/px) + HRSC (13m/px)

wiwf

ADAS

T

D

EH

EB RD

LRLD Wc

(x,y)

3. Morphometric variablesWhat to measure?

Introduction

Catalog Results: Maps and variablesMap of 255 landslides in Valles Marineris (complete for landslides A > 0.42 km2)

Population density

Logarithmic sizes!

Introduction

Variable distribution: Runout & mobility

Factors affecting distribution?-Canyon width-Geology-Fluvial/glacial/periglacial/hydrothermalprocesses

Introduction

Long runouts: H/L vs. Volume plot

High fluidization

Martian

Terrestrial

Icy/glacial

-Distinct behavioral groups

-Slope and position of saturated flows is v. different

-Martian data scattered-Seems to fit more closely to terrestrial avalanche

-However, break in slope at much larger volumes...

-What could this mean?Enhanced fluidization due to size

Introduction

Age vs. Size: Enhanced (ancient) fluidization?

Landslide ages as measured by Quantin et al. (2004)

-Small landslides appear at all ages-Larger landslides are more frequent in the past(bounded by red line)

-If larger landslides = more fluidized, andlarger landslides = older, then it follows thatolder landslides = more fluidized

Landslide emplacement not uniform in time!

Introduction

PART II: In-depth study of failure

Geological setting

Volumes & ages

Terrestrial analogs

Topographical analysisEmplacemen

t models

Build a 3D Digital Terrain

Model(DTM)

Now that we have an understanding of Martian landslides on a planetary scale...

CTX Image G02_019178_1717 (20m/px) Introduction

Geological Setting

Simple relative timeline:

1. Formation of trough

2. On-going rifting (normal faulting)

3. Hydrous conditions (channels) both on plateau and canyon floor

4. Landslides occurred (synchronously?)

5. Wind erosion (yardang, inverted channels, aeolian deposits in depressions)

Introduction

Volume and Ages

1 Ga

100 Ma

75.2+ -7.17.1 Ma

East Landslide, area=3.8x100 km2111 craters, N(1)=3.6x100 km-2

CF: Mars, Hartmann & Neukum (2001)PF: Mars, Ivanov (2001)Epochs: Mars, Michael (2013)

10-3 10-2 10-1 100 101Diameter, km

10-4

10-3

10-2

10-1

100

101

102

Cum

ulativ

e cr

ater

freq

uenc

y, km

-2

1. Surface/volume changes 2. Crater counting

Vf = 1.29 km3, 1.37 km3Vi = 2.1 km3, 5.4 km339-75% mass deficit

Can compare deposit volume (1) to the slope volume (2)

(1)

(2)

Introduction

Porosity in landslide source = ice reservoir?Age = Amazonian

Terrestrial Analogues I: Glacier Bay, 2014February 16th, Alaska (2014)

Main differences:Thickness: 200 m vs. 13mFloor topographyWall slope (30 to 0 vs. constant 14)Snow and ice-capped terrain (vs. traveling on rock)Uneven martian floorHeight of fall (m vs. km)

Introduction

H/L = 0.27 (M), 0.22 (GB)

primary flow lobe

longitudinal ridges

secondary flow lobe

primary flow lobe

spreading spreading

a) Martian west landslide b) Glacier Bay landslide (2014)

accumulated deposits

Terrestrial Analogues I

Longitudinal ridges are a classic glacial/Alaskan failure feature (very rarely occur elsewhere on Earth)

Exist in ~ 55% of Martian landslides

Shear velocities + basal lubrication: need a soft base and viscous layer(De Blasio 2014)

Introduction

Topography Analysis

What could have shaped these 3 distinct features (on both deposits)?

Introduction

Emplacement models: Deglaciation faulting

Introduction

Emplacement models: Debris detachment

Introduction

Emplacement models: Basal Scouring

Introduction

Glaciation Evidence: GCMs and Landforms

Introduction

Net surface gain of ice over a year (mm) [Madeleine et al. 2009]

1. Obliquity and Climate models

2. Geomorphological systems and landforms

Proposed extent of glaciation and supraglacial landslide[Gourronc et al. 2013]

Summary

PART I: Catalogue & large-scale

landslide statistics

PART II: DTM and small-scale landslide

features

1. Variety of scales/frequencies/formations2. Driving forces must exceed geological control3. Larger/mobile events in wider canyons4. Favorable conditions in these areas (volatiles)5. Larger landslides have larger mobilities6. These could be much older and suggest a more fluidized past (ie. glacial environment)

1. Ages places the landslides around 75 Mya2. Volume shows 3/4 of material could have contained ice3. Comparison to Glacier Bay shows very similar features4. Topographic analysis shows 3 distinct structures on both slides(relying on a soft, low-friction, widespread and transient layer)5. Emplacement models with ice can explain these6. Glaciation in Valles Marineris is supported both by geological evidence and GCMs

Introduction

Next steps...

Introduction