EAS 206 Quiz 4 (Mars)

Mars Atmosphere Compared to Earth’s

• thicker atmosphere

• More carbon dioxide

• Can get colder

• Less dense

• Less surface gravity

Mars Hemispheric Dichotomy

• Formed early in Mars’ history - mechanism unknown

• Relief along the escarpment = 2 – 3 km

• Fundamental problem in Mars geology

• Shows might have has Early plate tectonics from impact crater

Internal Structure of Mars

• liquid outer core, solid inner iron core

• surface rocks more dense than Earth

• Found from orbiting data

• molten silicate mantle - convecting

• Mostly sulfur

• Weak magnetic field – Remanent magnetization

• Km thick crust

Mars Southern hemisphere

• high number of impact craters

• Older rocks

• Records magnetic field

• Thicker than northern hemisphere

Mars InSight Mission

• Interior exploration using Seismic Investigations, Geodesy, and Heat Transport

• to understand formation and evolution of Mars, specifically crust thickness, size and form of core, tectonic activity

• Uses SEIS (Seismic Experiment for Interior Structure), HP3 (Heat Flow and Physical Properties Probe), RISE (Rotation and Interior Structure Experiment), APSS (Auxiliary Payload Subsystem)

Mars Pre-Noachian (4.56 – 4.15 Ga)

• 1st epoch

• Accretion and differentiation

• Magma ocean formation

• Degassing to make primordial atmosphere and hydrosphere

• Intense impact bombardment

• Formation of hemispheric dichotomy

• Formation of large basins (Hellas, Argyre, etc.)

Mars Noachian (4.15 to ~3.6 Ga)

• 2nd epoch

• Intense impact bombardment continues

• Northern lowland fills with lava and sediment

• Early volcanism

• Flood basalts

• Patera and other volcanoes

• Tharsis rise tectonism begins

• Radial grabens

• Valley networks - Hydrologic cycle

Different craters on Mars

• Bowl-shaped < 15 km

• Central peaks < 100 km

• Multiring > 100 km (Hellas)

Carter type unique to Mars

Rampart craters

• Formed by fluidized ejecta

• Ejecta makes hump

• Splashes of mud

• Sudden melting of ice in regolith

Patera (“saucer”)

A volcano of broad areal extent with little vertical relief, ex. Mars Tyrrhena Patera, Alba Patera

Mars Apollinaris Mons

• 5.4 km high volcano, with 80 km wide caldera

• Built up by both pyroclastic and effusive eruptions

• Active from Late Noachian to Late Hesperian

Mars Dendritic Valley Networks

• in the ancient highlands

• support the idea of an ancient hydrologic cycle

• Origin is debated: Denser atmosphere → rainfall → streams

• Might be formed from Groundwater seepage (spring)

  • Cove-shaped heads

  • Undissected areas between channels

Mars Hesperian (~3.6 to 3.2 Ga)

• 3rd epoch

• Heavy bombardment ceases

• Magnetic field (geodynamo) shuts down

• Continued uplift of Tharsis (tectonism and volcanism)

• Valles Marineris forms from mass wasting

• Elysium volcanoes start to form

• Continued filling of northern lowlands from erosion of highlands

• Catastrophic outflow channels into Chryse Planitia (Northern ocean?)

• Thinning of atmosphere, cooling

Mars Tharsis uplift

• forms Olympus mons - largest volcano is solar system

• Got big due to uplifting and mantle plumes

• Forms by partial melting building up over 2 million years

• Different from Earth because of a lack of plate tectonics

Mars Outflow channels

• Long deep channels concentrated along the dichotomy boundary are the result of catastrophic outflow

• Associated chaotic terrain

• Evidence for sudden release from under confining layer

• Heat from impact or volcanic eruption

• Ice holding up top layers collapses and melts and flows away

Did Mars have a Northern Ocean

• probably no

• Only would occur if all channels in the north were active at the same time

Mars Amazonian (~3.2 Ga to present)

• 4th epoch

• Polar icy deposits form and are modified over time, due to changes in obliquity

• Ongoing Elysium and Tharsis volcanism with lava flow

• Possible martian meteorite source rocks

• Mass movement

• Widening of Valles Marineris

• Wind erosion and deposition

Mars Rock Cycle

• Igneous rocks represent the starting point

• Some sedimentary rocks

• no metamorphic rocks because there is no plate tectonic activity

Mars mineral history per epoch

1. Pre-Noachian - neutral pH , clays

2. Noachian - acidic, sulfate

3. Hesperian -acidic, sulfate

4. Amazonian - anhydrous ferric oxide

Mars epochs in order from oldest to youngest

1. Pre-Noachian

2. Noachian

3. Hesperian

4. Amazonian

L_s

“solar longitude” of the Martian year, ex. one mars year = 687 earth days

Current Mars atmosphere

• Has variable temperature

• Low pressure

• Is mostly CO2 (96%)

• CO2 ice is stable (in places)

• CO2 freezes at 148 K (-125°C)

• Water ice clouds near north pole

Is liquid water stable on Mars today?

No, there is not enough pressure in the atmosphere, water would boil

Water on Mars

• Liquid water NOT stable at the surface

• Water vapour in atmosphere (tiny amount)

• Water ice in ground, polar caps

• Varies with season and latitude

Mars Hydrologic Cycle

• there is a daily frost cycle that forms an ice cap at the poles on ground ice

• Yearly cycle between polar ice caps

• More that 50% water ice is at the poles

• Ground ice is within the top 1 meter of crust

Mars Ground Ice Patterned Ground

Distinctive geometric patterns caused by freeze-thaw processes

• Found in high latitudes of Earth and Mars

Mars Subsurface Ice

Forms and holds up boulders, overtime ice becomes exposed and sublimates causing the boulders to roll down

• shows past of the planet

Mars polar caps

significant reservoirs of frozen water and carbon dioxide

• 4-6km thick

• Seasonal cap of CO2 ice in the spring and melts in the summer

• residual cap of H2O ice always present with inter-annual variations, losing more every year

• residual south polar cap is made of mostly water ice

• Leaves scarps when melting

What do Mars melting polar caps form?

• scarps

• Chasma Borealis

• Ring of dune from pushed sediment around the cap

• Polar layered deposits from blown material from polar cap in northern summer

Mars Polar Layered Deposits

Forms from sediment that gets blown around from ice caps and gets overlain by ice

Mars Climate Change

• caused by variations in “tilt” (obliquity)

  • Now: 23.5° - Past: 15 – 60°

• Explains layered terrain

• Low obliquity: colder poles with more ice

• High obliquity: Poles warmed, atmosphere thicker, sediment rich layers deposited, warm summer, high humidity

Mars Climate Change and obliquity differences

• Low obliquity: colder poles with more ice, cool summer, low humidity, “cold fingers on planet)

• High obliquity: Poles warmed, atmosphere thicker, sediment rich layers deposited, warm summer, high humidity, less ice, water ice gets distributed, more water vapour

Mars Eolian Processes (wind activity)

Wind is the dominant agent of erosion on Mars today

• dust storms

• dust devils

• yardangs

• dunes

Mars dust storms

• global

• Wind velocities of 200 km/h or more

• detected by Viking landers

• Wind erosion more intense, proceeds faster than on Earth

• turn into dust devils (mini tornadoes)

Mars Yardangs

linear ridges formed by eolian erosion of intervening valleys

Causes of Mars Mass Movement

gravity-driven downhill movement of unconsolidated material

Large-scale causes:

• Enlargement of canyons

• Development of chaotic terrain

• landslides in Valles Marineris

Small-scale causes:

• Gullies (aka Slope Streaks)

• Recurring Slope Lineae (RSL)

Mars Slope Streaks

• salt residue

• origin unclear

• Types: linear, curved, fan-shaped, splitting/branching

• A few meters to several km long

• Start in a point upslope, widen downslope

• Can appear at any time of year

• Occur in equatorial/subequatorial regions

• Form in a short time (minutes to hours)

• fade over years to decades

• Could indicate subsurface conditions conducive to life

Wet vs Dry Mars Slope Streaks causes

Wet (liquid water):

• Groundwater springs

• Melting frost/ice

• Brines or brine precipitates

Dry:

• Dust avalanching

• Subsurface melting

• Disturbances from rockfalls, impacts, or marsquakes

Mars SNCs meteorites

• S = Shergotty; “shergottites” (most common)

• N = Nakhla; “nakhlites”

• C = Chassigny; “chassignites”

  all witnessed falling to Earth

How do we know Mars meteorites come from Mars?

• Trapped atmospheric gases: match in composition and atmosphere is unique

• Young crystallization ages (>175 Ma): age shows presence of volcanic activity

• Oxygen Isotopes

• Glassy black pockets hold mars atmosphere

• Shockwaves causes veins in rocks by impact craters

How are Mars meteorites formed?

Impact craters cause material to get launched in certain conditions and land on Earth

Mars meteorite composition

Mafic igneous rocks

• Crystallized from basaltic magmas

• Higher iron (Fe), lower aluminum (Al)

• more enriched in volatile elements (Na, Mn)

• Some have “rust”: Fe-oxides and clay

• Alteration by water on Mars

Mars shergottites meteorite minerals

Basalts:

• sometimes olivine, (Fe,Mg)2SiO4

• pyroxene, (Ca,Fe,Mg)SiO3

• plagioclase feldspar, CaAl2Si2O8

• Oxides

Mars Tissint shergottite

• fragments found in Morocco

• Went around the sun a few times before falling on Earth

• Larger olivine grains in a matrix of pyroxene and plagioclase - “olivine-phyric”

• Oxygen isotopes show it is Martian

• Abundant shock veins and melt pockets

• Crystallized 574 Ma

• Ejected from Mars 0.7 Ma

Mars Clinopyroxenites (nakhlites) and Dunites (chassignites) meteorite mineral composition

Clinopyroxenites (nakhlites): Ca-pyroxene, olivine +alteration minerals

Dunites (chassignites): olivine, chromite

Martian Orthopyroxenites meteorite mineral composition

• Minerals:

  • orthopyroxene, (Fe,Mg)SiO3

  • Some carbonates (from alteration by water)

• 4.1 Ga old

• 3.9 Ga carbonates

• carbonate rosettes

Mars Basaltic breccia meteorites

• can see individual mineral grains

• Look like sedimentary rocks

• Clasts of basalt, orthopyroxenite, spherules, impact melts, siltstone

• Components very old

Mars Augite-rich shergottites meteorites

• Augite-plagioclase-magnetite basalt

• Highly oxidizing conditions

• Early olivine crystals have undergone an oxidation reaction

• Age ~2400 Ma

Mars meteorite significance

• only samples of Mars that we have until rocks are brought back by missions

shows:

• Igneous processes: Crystallization, cooling

• Mantle sources: Martian interior

• Surface processes: Alteration, weathering

Mars Pathfinder Mission

• low cost mission

• Launched December 4, 1996

• First use of airbags for landing

• Stationary lander called “Pathfinder”

• Rover called “Sojourner”

• Landed in the Ares Vallis area of Chryse Planitia

• Sample different rock types

Mars Pathfinder Mission Objectives

• Surface morphology and geology at the metre scale (Instrument: IMP)

• Petrology and geochemistry of surface materials (Instrument: APXS)

Mars Alpha Proton X-Ray Spectrometer (APXS)

Pathfinder Rover

• to analyze rocks and soil

• Results similar to Viking analyses

Imager for Mars Pathfinder (IMP)

Mars pathfinder lander

Mars Pathfinder Mission Results

• Rock compositions = basaltic andesites or andesites

• higher amount of silica

• High uncertainty

• Weathering? Adhered soil? Igneous? Unknown

Mars MER (Mars Exploration Rover) mission objectives

• clues to past water activity

• distribution and composition of minerals, rocks, and soils

• geologic processes

• validate orbital remote-sensing data

• quantify relative amounts of specific mineral types that contain water or hydroxyls

• mineral assemblages and textures of different types of rocks and soils

• clues where liquid water was present and if it was conducive for life

Mars MER (Mars Exploration Rover) mission instruments

• Panoramic Camera (Pancam)

• Miniature Thermal Emission Spectrometer (Mini-TES)

• Alpha-Particle X-ray Spectrometer (APXS) - characterizes elements

• Microscopic Imager (MI) - for rock texture

• Mössbauer Spectrometer

• Rock Abrasion Tool (RAT)

• Magnet Arrays

Mars MER (Mars Exploration Rover) mission mini-TES

Miniature Thermal Emission Spectrometer

• Works with Pancam

• Sees Infrared Radiation from rocks and soil

• Signatures of minerals

• Heat retention of rocks and soil

Mars MER (Mars Exploration Rover) mission Microscopic Imager

• on robotic arm

• For rock texture, and soil characteristics

Mars MER (Mars Exploration Rover) mission APXS

• On robotic arm

• Uses Curium 244 as radiation source, producing alpha particles and X-rays from the rock

• Characteristic of elements (all except H)

• Measurements taken at night

Mars MER (Mars Exploration Rover) mission Mössbauer Spectrometer

• On robotic arm

• Specialized to study Fe- bearing minerals

  • Composition and abundance

  • Ferrous (Fe2+) and ferric (Fe3+)

  • Magnetic properties

• Uses Cobalt 57 as radiation source

Mars MER (Mars Exploration Rover) mission Rock Abrasion Tool

• On robotic arm

• Get beneath dust/crust to fresh rock

• Compare fresh with weathered

Mars MER (Mars Exploration Rover) mission igneous results

• Basalt lava flows

• Explosive volcanic eruptions

• Impact ejecta materials

• water alterations

Mars MER (Mars Exploration Rover) mission sedentary results

• Basaltic sandstone cemented by sulfates

• Sulfate-rich sandstone with hematite concretions, deposited by wind and water

• Diagenesis (interaction with groundwater)

Mars MER (Mars Exploration Rover) mission

• lasted a long due to solar panels being cleared by dust

Two rovers landed:

• Spirit

  • Landed in Gusev Crater, 15 degrees south of the equator, a possible paleolake

• Opportunity

  • Landed in Meridiani Planum, a site of high hematite content

Mars meteorite bias

• mostly igneous

• Mostly Amazonian in age (<3400 Ma)

• From younger volcanic ages

• Actual crust is older and more sedimentary