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Lecture #20:•• Surface of MarsSurface of Mars

••Geology and Geologic ProcessesGeology and Geologic Processes••View from the SurfaceView from the Surface••History/Evolution of the surfaceHistory/Evolution of the surface

• Reading:–– Chapter 9.4Chapter 9.4

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The Main PointsMars has had a geologically active past

that has included volcanic, tectonic, impact, and erosional processes

Today, Mars geology is dominated by erosional processes, and we don’t know

if the planet is still volcanically or tectonically active

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Geology of Mars• Mars is a geologically exciting place!

– Abundant evidence of past volcanism– Abundant evidence of past tectonism– Abundant evidence of past impact cratering– Abundant evidence of past and current erosion

• Much of our knowledge comes from orbital imaging (Viking, MGS, Odyssey, MRO)

• Augmented at five specific landing sitesAstro 102/104 4

The View from the Surface• Three landers and two rovers have successfully returned images and other data

from the surface of Mars

– Viking Lander 1• 600 kg landed mass, powered by two 238Pu RTGs• Landing site: Chryse Planitia (22.697° N, 48.222° W)• Operated from July 20, 1976 to November 13, 1982

– Viking Lander 2• Landing site: Utopia Planitia (48.269° N, 225.990° W)• Operated from September 3, 1976 to April 11, 1980

– Mars Pathfinder• 360 kg landed mass (Rover = 16 kg), powered by solar panels• Landing site: Ares Valles (19.33° N, 33.55° W)• Operated from July 4, 1997 to September 27, 1997

– Mars Exploration Rovers (Spirit and Opportunity)• 174 kg mobile mass, powered by solar panels• Landing sites: Gusev Crater and Meridiani Planum • Operated from January 2004 to ???

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Viking Landers(1976-1982)

Frost at VL2

Trenches at VL2

VL1

Dunes, boulder at VL1 Astro 102/104 6

Mars Pathfinder (1997)

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Mars Exploration Rovers (2003-2008)

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Volcanism• Two large volcanic provinces on Mars

– Tharsis: An enormous 10 km bulge in the crust– Elysium: Smaller, localized elevated region

• Relative age dating from crater counts indicates that these volcanoes are relatively young (< 100 million years?)

• Mars may be volcanically active today, though we have not seen direct evidence...

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Olympus

Elysium

Lava flows in Tharsis

Lava flows thatpartially buriedanother volcano

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Tectonism• Spectacular rifting of the

Martian crust has occurred– Triggered by bulging of Tharsis?– Largest rift: Valles Marineris canyon system

• 5000 km long, 100 km wide, 8 km deep ( ~ 5 miles deep!!)

• Few signs of compression (e.g., folded or uplifted mountains)

• Speculations, but no conclusive evidence for Earth-like plate tectonics on Mars

Astro 102/104 11Rift Valley

CanyonsExtensional

Graben

FracturedTerrain Astro 102/104 12

Impact Cratering• Thousands of impact craters on Mars

– Sizes range from a few meters to 1500 km

• Many more craters in the south (older)

• But even "young" areas have many craters

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Impact Basins"Splosh" Craters

Degraded Craters

Radial Ejecta

"Pedestal"Craters

Craters onVolcanoes! Astro 102/104 14

Age of the surface based on craters• Craters used to

develop the stratigraphy of the Martian surface

• Absolute ages have large uncertainties

• Most recent volcanism: from 0.1 to 2.0 billion years ago?

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Erosional Features

• Evidence for substantial movement of materials on Mars– Gravity

• Landslides, Slumps, Ejecta Blankets– Wind

• Dunes, Streaks, Dust Storms, Dust Devils– Water

• Outflow channels, Runoff channels (valley networks)– Ice?

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Landslide

Outflow Channel

Runoff Channel

Streamlined “Islands”

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Seeps?

Dunes Wind Streaks

Dust Devil& Tracks

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Dust Devils in Motion…

This movie clip shows several dust devils moving from right to left across a plain inside Mars' Gusev Crater. The clip consists of frames taken by Spirit's navigation camera during the rover's 543rd martian day, or sol (July 13, 2005). The total time elapsed during the taking of these frames was 12 minutes, 17 seconds.

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Topography of MarsGeneral trend:North is low (blues); South is high (reds)Crater density: north "young", south "old"Reference elevation: 6.1 mbar pressure

• Enormous range of elevations on Mars!

• Highest high: +25 km (Olympus Mons)

• Lowest low: -5 km (Hellas Basin)

• Factor of 20 in atmospheric pressure!

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Mars Topography: • Broad range of elevations• Distinct northern/southern dichotomy

- Southern highlands; Northern lowlands

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The Martian Interior• The relatively low density (3.9 g/cm3) implies less

iron or metal in the interior than Earth or Venus• Mars appears to be differentiated• Spacecraft measurements of the

gravity field of Mars are consistent with the presence of a metallic core of radius 1300-2000 km (1/3 to 1/2 the planet's radius)

• No seismic networks on Mars (yet), so the existence of a core and details about the interior are still just theories...

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Is (or Was) Mars Magnetic?• Mars has no global magnetic field today• If Mars has (or had) a molten iron core like the Earth, then

why doesn't it have a magnetic field?

• Data from the Mars Global Surveyor mission reveal regions of the surface that appear to retain a remnant magnetism

• Was the core molten long ago?• Consistent with early volcanism• But what does it mean?

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Summary• Mars is a fascinating geologic world

– Largest volcanoes in the solar system– Enormous rift valleys and canyon systems– Complex impact structures on all scales– Active erosion by wind and gravity– Extensive erosion by water early in Mars history?

• 3 landers and two rovers have studied the environment in detail

• Spacecraft data indicate that Mars is differentiated• Will humans one day go to Mars…?

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Next Lecture...•• Martian Climate Change?Martian Climate Change?

•• The Martian ClimateThe Martian Climate–– Evidence for climate changeEvidence for climate change–– Did it rain on Mars?Did it rain on Mars?–– Implications for Earth's climate...Implications for Earth's climate...

•• Reading:Reading:–– Chapter 10.4Chapter 10.4