Mondradius: 1.737 km Erdradius: 6.378 km - dlr.de€¦ · Lava (Lunar Mare-Basalts) E. Hauber: Vulkanismus und Tektonik, Ringvorlesung HGF-Allianz „Planetenentwicklung und Leben“,

Erde und Mond– maßstäblich

Mondradius: 1.737 kmErdradius: 6.378 km

E. Hauber: Vulkanismus und Tektonik, Ringvorlesung HGF-Allianz „Planetenentwicklung und Leben“, TU Berlin, 23. April 2009

Lunarer Vulkanismus(Mare Basalts)

17% der Oberfläche1% des Krustenvolumens

Relativ geringer Grad der Teilschmelzen im

Mantel


Lava (Lunar Mare-Basalts)Lava (Lunar Mare-Basalts)


Sinuous Rilles

Eruption rates:~1000 km3/a

for comparison:Vesuv, Kilauea:Average peak flux:~10-2 km3/a

E. Hauber: Vulkanismus und Tektonik, Ringvorlesung HGF-Allianz „Planetenentwicklung und Leben“, TU Berlin, 23. April 2009E. Hauber: Vulkanismus und Tektonik, Ringvorlesung HGF-Allianz „Planetenentwicklung und Leben“, TU Berlin, 23. April 2009

there wereshort-lived periodsof high volcanicactivity on theMoon

Emplacements of Lunar Mars Basalts

from Head and Wilson (1992)


Timescales on Moon and Mercury

from Head et al., Space Sci. Rev. (2007)


Gruithuisen-Domes(Apollo)


Mond: SchildvulkaneMond: Schildvulkane

Vulkanismus auf dem Mond

• Relativ wenig Volumen• Niedrige Effusionsraten (über lange

Zeiträume)• Kurzfristig hohe Eruptionsraten• Niedrige Viskosität der Laven• Dadurch weite Fließstrecken• Enorme zeitliche »Streckung«• Zusammensetzung variiert mit der Zeit• keine regionalen Tendenzen• Chemismus evtl. deutlich variabler


Extensional features:

Lunar GrabensExtensional features:

Lunar Grabens

•A

po

llo A

S1

0-3

1-

46

45

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po

llo A

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Contractional Features:

Wrinkle ridgesContractional Features:

Wrinkle ridges


Mare Serenitatis

Mantel

KrusteIIIIII

Gräben entlangder Beckenränder

Dikes

Gräben entlangder Beckenränder

Wrinkle Ridges;durch KompressionentstandenGraben GrabenWrinkleridges

Mantle

CrustDikes

Dehnung Dehnung

Stauchung



Moon: Summary of tectonic structures

• »simple« tectonic evolution

• early extension (>3.5 Ga) and later contraction (<3.5 Ga)

• Loading-induced tectonism

– Concentric grabens at edges of basins

– Downwarping of basin centers wrinkle ridges

• Tidal forces

– Despinning: predictions of fracture pattern (e.g., Melosh, 1977)

– But no such patterns observed on the Moon

• Impact-induced tectonism• Review paper: Hiesinger & Head, in: New Views of the Moon (2006)


Mercuryimage from http://messenger.jhuapl.edu

E. Hauber: Vulkanismus und Tektonik, Ringvorlesung HGF-Allianz„Planetenentwicklung und Leben“, TU Berlin, 23. April 2009

Was there volcanism on Mercury?

• Spectra are nearly featureless surface analogous to lunar anorthositic crust? (Tyler et al., 1988; Sprague et al., 1994)

• Some evidence from Mariner 10 colour data (Robinson and Lucey, 1997), stratigraphic relations, and morphology areinterpreted to be consistent with volcanically emplacedmaterials (e.g., Spudis and Guest, 1988)

• Comparison with Moon: no volcanic features could havebeen identified on the Moon in images with resolutions of Mariner 10 (Milkovich & Head, 2002) the question of volcanism on Mercury was open until MESSENGER arrived


Past evidence: Embayment relationships and ponding in topographic lows

Tolstoj basin (17°S, 196°E) Mare Humboldtianum (56°N, 280°E)

MercuryMercury MoonMoon

from Head et al., Space Sci. Rev. (2007)


…and then MESSENGER arrived:

A volcano on Mercury

from Head et al., Science (2008)


Collapse: Evidence for volcanism?

• Crater diameter: 52km

• „telephone“-shaped collapsefeature: pastvolcanic activityat and just belowthe surface?

image from http://messenger.jhuapl.edu


Pantheon Fossae

• troughs radiating outward in a geometry unlikeanything seen by Mariner 10.

• extension ? • Other troughs near the center form a polygonal

pattern (also seen along the interior margin of Caloris).

• impact crater (~40 km) centered on PatheonFossae

• straight-line segments of crater walls influencedby preexisting extensional troughs?

• Dike swarm?

• troughs radiating outward in a geometry unlikeanything seen by Mariner 10.

• extension ? • Other troughs near the center form a polygonal

pattern (also seen along the interior margin of Caloris).

• impact crater (~40 km) centered on PatheonFossae

• straight-line segments of crater walls influencedby preexisting extensional troughs?

• Dike swarm?

Image : NASA/Johns Hopkins University APL/Carnegie InstitutionImage : NASA/Johns Hopkins University APL/Carnegie Institution


Tectonics of MercuryTectonics of Mercury


Extensional features: Grabens

• rare• associated with Caloris basin• but new results from MESSENGER?

• rare• associated with Caloris basin• but new results from MESSENGER?

Image: Mariner 10


Contractional features on Mercury

• Lobate scarps

– Steeply sloping scarp face and gently slopingback scarp

• Wrinkle ridges

– Mainly on the floor of Caloris and in smoothplains surrounding Caloris

• High-relief ridges

– Symmetric in cross-section

– Surface expression of high-angle reverse faults?


Lobate scarps and high relief ridges• Linear or arcuate

features

• Relief hundreds of meters to > 1km

• Length tens to hundreds of kilometers

• Offsets in craterwall and floormaterials suggestsurface breakingthrust faults

• Planar geometry

from Watters et al., Geophys. Res. Lett. (2004)


Discovery Scarp

Image courtesy of Mark Robinson


Lobate scarps• Older studies: lobate scarps due to global contraction

due to cooling of planetary interior compressionalstrain is ~0.056% (radius decrease <1 km) e.g., Watterset al., Geology (1998)

• Lobate scarps are not randomly distributed (but: pre-MESSENGER knowledge!)

• Initiation of widespread thrust faulting only afterCaloris formation and formation of Calorian smoothplains (<3.9 Ga ago)

• Regional-scale tectonic stresses may have dominatedover stresses resulting from global contraction

from Watters et al., Geophys. Res. Lett. (2004)


Summary• Several models for lobate scarp

formation

– Global contraction due to interiorcooling

– Tidal despinning

– Interaction of thermal stresses and Caloris-induced stresses

• All models have limitations in explaining spatial and temporal distribution of lobate scarps

• No features indicative of large mantle swells (like Tharsis) or intermediate-scale mantle activity (like coronae)

• Review paper: Head et al., Space Sci. Rev. (2007)

• MESSENGER analysis ongoing! Stay tuned!


Documents

Mondradius: 1.737 km Erdradius: 6.378 km - dlr.de€¦ · Lava (Lunar Mare-Basalts) E. Hauber: Vulkanismus und Tektonik, Ringvorlesung HGF-Allianz „Planetenentwicklung und Leben“,