Lecture 3: Tectonics of icy satellites › image › PPT3-Yin An 2016.pdf · 2016-03-28 · Leading Edge Terrain: Key Features 1. Many relic domains of Cratered Terrain bounded by

Lecture 3: Tectonics of icy satellitesLecture 3: Tectonics of icy satellites

Galilean moons of Jupiter

Icy SatellitesIcy SatellitesRocky SatelliteRocky Satellite

Lineae (English: lines): dark streaky fractures crisscrossing the entire globe

Cycloid ridges

Cycloid ridges

If Europa rotates non-synchronously, it can produce a considerable amount of stress.

The variation of tides can be described by two traveling waves moving counterclockwise (c) and clockwise (d).

Greenberg, Richard, et al. "Tectonic processes on Europa: Tidal stresses, mechanical response, and visible features." Icarus 135.1 (1998): 64-78.

Hoppa, G. V., Tufts, B. R., Greenberg, R., & Geissler, P. E. (1999). Formation of cycloidal features on Europa. Science, 285(5435), 1899-1902.

“Lenticulae" (Latin for "freckles") on Europa

Reddish “freckle” spots are ~ 10 km across

Popped blisters?

Un-popped blisters?

Lenticulae are considered to be a result of rising plumes

Sotin, C., Head, J. W., & Tobie, G. (2002). Europa: Tidal heating of upwelling thermal plumes and the origin of lenticulae and chaos melting. Geophysical Research Letters, 29(8), 1233.

Chaos terrains: fragmented striated ice crust flowing like icebergs

Broken ice shelf at Arctic ocean north Greenland

Double ice-ridge fractures

Opening up with the gapFilled by new ice

Possible relationships between surface morphology and deep processes below on Europa

Offset of a linear band by strike-slip faults

Reddish “freckle” spots are ~ 10 km across

10 km

Cryolava

Potential for extraterrestrial life: a top location with the possibility of hosting extraterrestrial life. Life could exist in its under-ice ocean, similar to Earth's deep-ocean hydrothermal vents.

• Black smokers: centers of ecosystems in deep seas where sunlight is nonexistent

• Organisms convert heat, methane, and sulfur into energy (i.e., chemosynthesis).

• New and unusual species are constantly being discovered in the neighborhood of black smokers.

Freaky Deep-Sea-Dwelling Bristle Worm



http://scitechdaily.com/images/New-View-of-Jupiters-Moon-Ganymede.jpg

“Grooved terrain” on Ganymede

100 km



40 km

Mean radius: 2410 km, very similar to that of Mercury (~2440 km)

The surface of Callisto is heavily cratered and extremely old.

It does not show any signatures of tectonism.

Galilean moons of JupiterGalilean moons of Jupiter’’s satellites: Surface Morphology s satellites: Surface Morphology Icy SatellitesIcy SatellitesRocky SatelliteRocky Satellite

It has its own intrinsic magnetic field

SaturnSaturn’’s regular moons include the seven major satellitess regular moons include the seven major satellites

Source: http://photojournal.jpl.nasa.gov/jpeg/PIA19058.jpg

EnceladusEnceladus

Spencer and Nimmo (Ann. Rev. Earth Planet. Sci. 2013)Spencer and Nimmo (Ann. Rev. Earth Planet. Sci. 2013)


Thermal emissivity map of the South Polar Terrain

Spencer, J. R. et al. (2009). in Saturn from Cassini-Huygens: Enceladus: an active cryovolcanic satellite, edited by Dougherty, M., Esposito, L. & Krimigis, S., Springer, Netherlands, pp. 683–724.

Surface age of less than a few million years in the south polar terrain, a > 1-2 Ga elsewhere.

Tiger stripes are 2 km wide with a trough ~0.5 km deep.


HorseheadHorsehead

HorsetailHorsetail

HorseheadHorsehead

HorsetailHorsetail

Twiss and Moore (2005)

LeftLeft--slip faulting along tigerslip faulting along tiger--stripe fracturesstripe fractures

En echelon normal faults/extensional fracturesEn echelon normal faults/extensional fractures

En echelon foldsEn echelon folds

South Polar South Polar TerrainTerrain

Leading Leading Edge Edge TerrainTerrain

Trailing Trailing Edge Edge TerrainTerrain

CrateredCrateredTerrainTerrain


http://www.jpl.nasa.gov/edu/images/news/enceladus_tigerstripes.gif

Key questions to be discussedKey questions to be discussed

1.1. How did the South Polar Terrain form? How did the South Polar Terrain form?

2.2. How does it fit into the global How does it fit into the global evolution?evolution?

Cratered Cratered TerrainTerrain

Background Information: Cratered TerrainBackground Information: Cratered Terrain

Cratered Cratered TerrainTerrain


40 km40 km


Thermal relaxation common

Leading Edge Leading Edge TerrainTerrain

Background Information: Leading Edge TerrainBackground Information: Leading Edge Terrain

Leading Edge Terrain: many relics of Cratered TerrainLeading Edge Terrain: many relics of Cratered Terrain

Close up view of the relics of Cratered TerrainClose up view of the relics of Cratered Terrain

Relic cratered domains are bounded by shear Relic cratered domains are bounded by shear zones accommodating rotationzones accommodating rotation

Margins to Cratered Terrain are mostly transitional Margins to Cratered Terrain are mostly transitional

Leading Edge Terrain: Key FeaturesLeading Edge Terrain: Key Features

1.1. Many relic domains of Cratered Terrain Many relic domains of Cratered Terrain bounded by shear deformation zones. bounded by shear deformation zones.

2.2. Margins are mostly transitional to the Margins are mostly transitional to the Cratered Terrain. Cratered Terrain.

3.3. No throughNo through--going brittle strikegoing brittle strike--slip fractures slip fractures zones similar to the tigerzones similar to the tiger--stripe fractures in stripe fractures in the South Polar Terrain. the South Polar Terrain.

Interpretation: (1) Mechanical fragmentation of ice Interpretation: (1) Mechanical fragmentation of ice shell; similar to formation of the Chaos shell; similar to formation of the Chaos Terrain on Europa. (2) Weak or shorter Terrain on Europa. (2) Weak or shorter duration of thermal event leading to duration of thermal event leading to incomplete resurfacing. incomplete resurfacing.

Trailing Edge Trailing Edge TerrainTerrain

Background Information: Trailing Edge TerrainBackground Information: Trailing Edge Terrain

Background Information: Trialing Edge TerrainBackground Information: Trialing Edge Terrain

Arcuate mountain belts and internal ridgesArcuate mountain belts and internal ridges

Linear mountain beltLinear mountain belt

Closely spaced ridgeClosely spaced ridge--trough systemstrough systems

Troughs bounded by sharp linear scarpsTroughs bounded by sharp linear scarps

Background Information: Trailing Edge TerrainBackground Information: Trailing Edge Terrain

Compressional Compressional domaindomain

Extensional Extensional domaindomain

Trailing Edge Terrain: Key FeaturesTrailing Edge Terrain: Key Features

1.1. Margins are marked by mountain belts and Margins are marked by mountain belts and extensional ridgeextensional ridge--trough zones. trough zones.

2.2. Interior has a compressional domain expressed by Interior has a compressional domain expressed by high relief ridges (folds) and an extensional high relief ridges (folds) and an extensional domain expressed by low relief troughs (grabens). domain expressed by low relief troughs (grabens).

3.3. No throughNo through--going brittle strikegoing brittle strike--slip fractures slip fractures zones similar to the tigerzones similar to the tiger--stripe fractures in the stripe fractures in the South Polar Terrain. South Polar Terrain.

Interpretation: (1) Thermal event long or strong Interpretation: (1) Thermal event long or strong enough to nearly completely resurface the crust. enough to nearly completely resurface the crust. (2) Formation process similar to that for the South (2) Formation process similar to that for the South Polar Terrain, with unidirectional translation and Polar Terrain, with unidirectional translation and internal deformation of an iceinternal deformation of an ice--shell sheet. shell sheet.


Background Information: South Polar TerrainBackground Information: South Polar Terrain

South Polar Terrain

AS

TE LE

SSTE M

argin

TE Margin

LE Margin

LE Margin

SS Margin

SS Margin

AS Margin

AS MarginCTCT

CTCT

LETLET

TETTET

CT: CT: Cratered TerrainLET: LET: Leading Edge TerrainTerrainTET: TET: Trailing Edge Terrain

AS

TE LE

SS

TE Margin

TE Margin

LE Margin

LE Margin

SS Margin

SS Margin

AS Margin

AS Margin

Key features of the South Polar TerrainKey features of the South Polar Terrain

Trailing edge margin: parallel roundTrailing edge margin: parallel round--top ridgestop ridges

Leading edge margin: parallel sharpLeading edge margin: parallel sharp--edge scarpsedge scarps

Interior domain: TigerInterior domain: Tiger--stripe fracturesstripe fractures

AntiAnti--Saturnian margin: Oblique roundSaturnian margin: Oblique round--top ridges top ridges and sharpand sharp--edged scarps edged scarps

Marginal zones: compression, extension, right slip, and Marginal zones: compression, extension, right slip, and left slip.left slip.

Interior: five tigerInterior: five tiger--stripe fractures are leftstripe fractures are left--slip faults.slip faults.

Uneven extension along the Leading Edge margin caused Uneven extension along the Leading Edge margin caused internal clockwise rotation and distributed rightinternal clockwise rotation and distributed right--slip shearing. slip shearing.

Uneven extension in the LEM caused internal clockwise Uneven extension in the LEM caused internal clockwise rotation of the South Polar Terrain. This boundary condition in rotation of the South Polar Terrain. This boundary condition in turn led to turn led to ““bookshelf faultingbookshelf faulting””. .

RightRight--slip shear slip shear causes leftcauses left--slip slip faultingfaulting

(1) Initial Configuration

(2) Final Configuration

Y-shaped crack

““BookshelfBookshelf”” faulting driven by gravity faulting driven by gravity

Digital topographic model from Schenk and McKinnon (2009)

What is the origin of the South Polar Terrain? What is the origin of the South Polar Terrain?

2 cm2 cm

Sliding dry sand over viscous putty on an inclined planeSliding dry sand over viscous putty on an inclined plane

NormaNormal fault l fault scarpsscarps(= (= LEM)LEM)

LeftLeft--slip slip faultsfaults( = ( = TSF?)TSF?)

Fold Fold beltbelt(TE(TEM)M)

South Polar Terrain: Key FeaturesSouth Polar Terrain: Key Features

1.1. Four margins marked by paired Four margins marked by paired compression/extension and rightcompression/extension and right--/left/left--slip fault zones. slip fault zones.

2.2. Interior marked by five leftInterior marked by five left--slip slip faults. faults.

Interpretation: Unidirectional flow Interpretation: Unidirectional flow with internal domain rotated with internal domain rotated clockwise, causing bookshelf clockwise, causing bookshelf faulting. faulting.


Leading Leading Edge Edge TerrainTerrain

Trailing Trailing Edge Edge TerrainTerrain



How did Enceladus How did Enceladus evolve with timeevolve with time

How did Enceladus How did Enceladus evolve with time? evolve with time?

1.1. Leading Edge Terrain: Leading Edge Terrain: Pervasive mechanical Pervasive mechanical fragmentation of the ice shell. fragmentation of the ice shell.

2.2. Trailing Edge Terrain: Trailing Edge Terrain: A sheet of deformable A sheet of deformable ice shell moved unidirectionally creating ice shell moved unidirectionally creating paired extensional and compressional domains; paired extensional and compressional domains; no discrete strikeno discrete strike--slip faults formed. slip faults formed.

3.3. South Polar Terrain: South Polar Terrain: A sheet of deformable ice A sheet of deformable ice shell moved unidirectionally with formation of shell moved unidirectionally with formation of discrete strikediscrete strike--slip faults. slip faults.

South Polar TerrainSouth Polar Terrain(youngest)(youngest)

Leading Leading Edge Edge TerrainTerrain(second (second or third or third oldest)oldest)

Trailing Trailing Edge Edge TerrainTerrain(second (second or third or third oldest)oldest)

CrateredCrateredTerrainTerrain(oldest)(oldest)

CrateredCrateredTerrainTerrain(oldest)(oldest)

Sequence of major Sequence of major geologic events on geologic events on EnceladusEnceladus

Speculation: Speculation: If mechanical fragmentation and If mechanical fragmentation and incomplete resurfacing was followed by incomplete resurfacing was followed by viscous flow of iceviscous flow of ice--crust sheets and nearly crust sheets and nearly completely resurfacing, Enceladus appears completely resurfacing, Enceladus appears to have been warming up or punctuated to have been warming up or punctuated thermal events became longer. thermal events became longer. Does it say anything about the Does it say anything about the eccentricity history of the satellite and/or eccentricity history of the satellite and/or evolution of heating mechanisms ? evolution of heating mechanisms ?

SaturnSaturn’’s regular moons include the seven major satellitess regular moons include the seven major satellites

Basic facts about Iapetus: Basic facts about Iapetus:

Saturn’s third-largest moon with a radius of 734 km.

Leading side is 10 times darker than parts of the trailing side caused by impact-induced coating or sublimation lag.

~10 km high equatorial ridge system and the topographic relief is from -10 km to + 13 km.

Most of the topography is older than 4 Ga.

Cassini image PIA08404 from http://photojournal.jpl.nasa.gov/target/iapetus

The ridge is about 10 km higher than the surrounding regions.

Ip, W. H. (2006). On a ring origin of the equatorial ridge of Iapetus. Geophysical research letters, 33(16).

The ring-accretion mode of Ip (2006): the ridge is too narrow to be explained by this mechanism

Sandwell, D., & Schubert, G. (2010). A contraction model for the flattening and equatorial ridge of Iapetus. Icarus, 210(2), 817-822.

t = 0 m.y.: accretion with an initial radius of r0 and an average porosity of 10%.

t = 200 m.y.: internal heating causes ductile flow moving inwards causing north-south compression and ridge formation through buckling.

Lecture 3: Tectonics of icy satellites › image › PPT3-Yin An 2016.pdf · 2016-03-28 · Leading Edge Terrain: Key Features 1. Many relic domains of Cratered Terrain bounded by

Documents