Midterm Flashcards

Question

What are the different planetary science methods?

Answer 1

1. Planetary Geomorphology –Creating geologic maps from satellite data –Laboratory and computer simulations of geological processes in different planetary environments –Analogue studies 2. Spacecraft Data –Remote Sensing Data * Visible, hyperspectral, thermal, altimeter, and RADAR

Answer 2

■A geological map shows rock units, rock ages or geological strata depicted by color or symbols ■Maps rock units exposed at the surface ■Contour lines may be used to show topography

Answer 3

Areas on Earth with geological conditions such as geological, environmental or biological conditions that may approximate the past or present conditions on extraterrestrial bodies (Mars / Moon) –Desert Research (Black Point Lava Flow, Arizona) –Underwater off Key Largo Florida –Pavilion Lake Research Project (BC) –Mauna Kea (Hawai’i) Inflatable Lunar Habitat Analog Study (Antarctica

Answer 4

Remote sensing is the science of obtaining information about objects or areas from a distance –typically from aircraft or satellites

Answer 5

Spectroscopy is the study between the interaction of matter and electromagnetic radiation

Answer 6

Laboratories with equipment that can simulate conditions on or within other planetary bodies –Example: High temperature gas-mixing furnace or multi-anvil cell (high pressure experiments)

Answer 7

■Remote sensing data makes use of electromagnetic radiation (EMR) ■Remote Sensing instruments are designed to detect specific parts of the EMR spectrum –Three main types: –UV-VIS –VIS-NIR - TIR

Answer 8

■Spectroscopy is the study of spectra ■Imaging spectroscopy is the study of images (usually the surface of a planetary body) composed of spectra ■Passive systems use natural radiation (sunlight); active systems use an artificial energy source (radar or laser altimeter) ■Imaging spectroscopy works with reflectance spectra * Incoming light is reflected off the surface and its spectrum is altered based on the interaction with surface material

Answer 9

■Most imaging systems use charge-coupled devices (CCDs) –CCD chip has an array of pixels onto which light is focused by a lens causing a pattern of electrical charges to be received –Light focused on the chip creates a pattern of electrical charges – the charge on each pixel is proportional to the amount of light received ■Simple systems = single wavelength (λ) range ■Wavelength range can be narrow or “broadband” ■Color images are produced by obtaining data for more than one wavelength over the same scene - Red-Blue-Green (RGB) frames combined to produce a colour image

Answer 10

In the visible near infrared (VNIR) minerals absorb energy –Absorption bands –Characteristic of specific minerals or groups of minerals –Multispectral spectrometers measure the reflected energy as a function of wavelength

Answer 11

■Surfaces emit or radiate energy (“heat”) in the infrared range of the EM spectrum, which can be recorded as digital files and transformed into images ■Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) uses a similar approach to map the distribution of minerals on Earth ■Thermal Emission Imaging System (THEMIS) ■Images in infrared and visible parts of the EM spectrum at 9 different wavelengths (λ) –8 have λ between 6 and 13 micrometers (ideal region of infrared spectrum to determine the thermal energy patterns for silicate minerals) ■THEMIS has a high spatial resolution (100 m) with a low spectral resolution ■THEMIS also has a visible imaging camera that acquires data in five spectral bands with a spatial resolution of 18 m / pixel * ■Intermediate between: –Viking Orbiters (150 to 300 m per pixel) –Mars Orbiter Camera (MOC) onboard Mars Global Surveyor (1.5 to 3 m per pixel) ■TES has a low spatial resolution (3x6 km) with very high spectral resolution of 143 bands between 5 and 50 micrometers

Answer 12

■High Resolution Imaging Science Experiment : exploring Mars one giant image at a time –Camera onboard Mars Reconnaissance Orbiter (MRO) –0.3 meters per pixel

Answer 13

■Bounce a laser off the surface and record two-way return time –Locations closer to the satellite have a shorter two-way return time ■Used to map elevation

Answer 14

■Without Radar we would know nothing about the surface of Venus and Titan, otherwise obscured by clouds ■Radar = Active remote sensing technique ■Radar systems mounted on airplane / spacecraft send short pulses of radio waves obliquely, striking the surface at an angle ■Reflected energy received as an echo ■Several thousand pulses / second at speed of light

Answer 15

■Spectrometers –VIS-NIR –TIR –Mössbauer –APXS –XRD ■Cameras –Panoramic –High-res ■Scoops, RATs, brushes ■Chemical analysis suites ■Wind/weather suite ■Sky observation ■Geothermal detection ■Seismic detection

Answer 16

■Atmospheric chemistry suite ■Altimeter ■Accelerometers ■Cameras ■RADAR

Answer 17

process of separating different constituents of a planetary body as a consequence of their physical and/or chemical behavior

Answer 18

■Goldschmidt (1937) classified the elements into four groups based on the way in which the elements distribute themselves among iron liquid, sulfide liquid, silicate liquid, and a gas phase

Answer 19

■In magma ocean, dense elements sink and light elements rise ■Dense iron diapirs (blobs) accumulate in core taking siderophile (iron loving) elements downward –Also some chalcophile (sulfur loving) elements ■Lighter silicate material migrates towards the surface –Buoyant molten rock rose to the surface; take lithophile silicate loving) elements –Si, Al, Ca, Na, K, Fe and Mg ■Result: Layering by chemical composition: –Crust –Mantle –Core

Answer 20

■Continued tectonic activity on Earth is driven by asthenospheric convection in response to temperature differences ■Heat sources: –Conversion of the kinetic energy of planetesimals into heat during impact –Decay of naturally-occurring radioactive elements (long and short-lived) –Compression of the Earth as its mass continued to rise –Release of gravitational potential energy by molten iron sinking toward the center of the Earth –Tidal heating (Earth-Moon)

Answer 21

■Divergent boundaries or spreading centers –lithosphere being pulled apart ■Convergent boundaries –lithosphere crunching together –subduction zones or collisional boundaries ■Transform fault boundaries –plates slide past each other

Answer 22

* reverse or thrust fault * strike slip faults * folds * ductile formations * Not sure this is right or everything difficult to tell from notes because there are notes on compression, tension and shearing

Answer 23

■Zones of up-ward converging convection (mantle hot spot or divergent plate boundary) tend to erupt mafic lava (Mg- and Fe-rich) –Partial melting of ultramafic mantle generates mafic melt ■Volcanoes associated with subduction tend to erupt intermediate and felsic lava (more Si-rich) –Fractional crystallization in a magma chamber and / or assimilation of felsic crust drives magma compositions towards enrichment in silica NOT sure if this is correct only thing in the right area of the lecture that I could find

Answer 24

■Explosive –Driven by the release of gases in the magma as it reaches the surface –Release pyroclastic materials (glass, ash, mineral & lithic fragments, spatter, bombs) ■Effusive –Magma erupted on the surface as liquid (low viscosity) lava flows

Answer 25

1. Shield Volcanos ■Very low angle slopes –Basaltic lavas ■Lower silica, lower viscosity, lava flows farther ■Largest volcanoes / mountains on Earth & in solar system 2. Stratovolcanos ■Large conical shaped ■Steep slopes (6-10º at base, 30º at summit) –Typically andesitic lavas –More silica, more viscous, don’t flow as far ■Layers of lava and tephra (ash) 3. Lava Domes and Block Lavas ■High viscosity felsic lavas don’t readily flow, but rather they build up lava domes or block lavas 4. Cinder Cones ■Built from particles and chunks of congealed lava ejected from a single vent ■Often small –Rarely more than ~1000 ft high ■Can be on the flanks of other volcanoes ■Common in volcanic terrains 5. Lava Tubes and Pit Craters ■Lava tubes are conduits that develop as roofed channels in some basalt flows –Insulate lava and allow it to flow great distances from the main vent ■When conduits are emptied the roof can collapse and produce a chain of small collapse features (\<1 km) called pit craters 6. Volcanic Calderas ■Volcanic craters with diameters \>2 km are called calderas which can form by collapse, explosion, erosion or a combination of these processes

Answer 26

■Two (or more) plates moving away (diverging) from each other –Creates long, narrow fractures –Magma from the mantle rises to fill the gap as the crust is ripped apart –Magma cools to produce new crust –Repeat ■Also called spreading centres ■Occur in oceans and in continents

Answer 27

■Two plates converging –Crust is destroyed or deformed ■Also called subduction zones ■Three types: –Ocean-ocean –Ocean-continent –Continent-continent

Answer 28

■Two plates slide past each other horizontally ■No creation or destruction of lithosphere ■Discovered by Canadian geoscientist J. Tuzo Wilson in 1965 –Proposed that they connect two spreading centres or subduction zones ■Most occur on the ocean floor but some occur on land

Answer 29

A big (\>1 meter) rock or aggregation of rocks in orbit around the Sun

Answer 30

A small (\<1 meter) rock orbiting the Sun

Answer 31

* The visible light that occurs when a meteoroid passes through the Earth’s atmosphere * It is an atmospheric phenomenon

Answer 32

■A rock found on Earth that was once a meteoroid ■A revised, more technical definition of meteorite is: “A natural, solid object larger than 10 microns in size, derived from a celestial body, that was transported by natural means from the body on which it formed to a region outside the dominant gravitational influence of that body and that later collided with a natural or artificial body larger than itself (even it if was the same body from which it was launched).” Rubin and Grossman (2010) Meteoritics & Planetary Science, v. 45:114-122.

Answer 33

■an exceptionally bright meteor –Heat from friction and rapid compression of air in front of the meteor –Produces light (colours may vary)

Answer 34

* **Fusion crust** is a thin, glassy rind on the exterior of the stone formed by melting during heating as it transits earth’s atmosphere * **Regmaglypts** thumb-shaped depressions on exterior from uneven melting

Answer 35

Meteorites are classified based on mineralogy, texture and composition into 1) stones (abundance 94%) 2) stony-irons (1%) 3) irons (5%)

Answer 36

* Main asteroid belt (Mars-Jupiter) * Moon * Mars * Parent body = the solid object from which the meteorite originated

Answer 37

The general sequence of events in an impact involves: (a) the initial contact of the bolide (projectile) with the target, resulting in (b) ejection of target material, (c) vaporization of parts of both the target and projectile, (d) formation of the transient cavity, and (e,f) the post-impact modifications, such as slumping of the crater walls and rebound of the crater floor

Answer 38

■vector sum of the impactor’s heliocentric velocity and Earth’s orbital velocity –Maximum possible impact velocity for Earth = 42 km/s + 30 km/s = 72 km/s –Typical Earth encounter velocities for asteroids are 15 – 25 km/s (Chyba et al., 1994 Hazards Due to Comets and Asteroids, Univ. of Arizona, pp. 9-58.)

Answer 39

■the free-fall velocity of a meteoroid due to the Earth’s gravitational attraction after it has been slowed by interaction with the atmosphere

Answer 40

a pit, hole or indentation formed by a free-falling meteoroid

Answer 41

impact of a meteoroid / asteroid traveling at greater than the free-fall velocity, this causes the propagation of a shock wave in both the impactor (asteroid) and target to produce an impact crater

Answer 42

1. Known impact craters on Earth (example: Meteor Crater, Arizona) 2. Nuclear and chemical explosion craters 3. Craters produced in hypervelocity impact experiments in the laboratory

Answer 43

1 – contact / compression stage the generation of a shock wave that expands radially from the point of contact. Decompression of the target after passage of the shock wave sets material into motion along excavation flow-paths and ejection of material to form the crater cavity. The most intense deformation occurs closes to the point of contact, leading to vaporization and melting of material; with distance from the point of contact, rocks are shock metamorphosed, fractured and brecciated 2 – excavation stage 3 – modification stage

Answer 44

* Non-circular craters - * are rare * Impacts are most like explosions – spherical shock wave leads to circular craters * Only very oblique (\>75°?) impacts cause non-circular craters * Not understood prior to the space age – argument against impact craters on the Moon

Answer 45

Most stages are similar to the simple crater example, with the exception of development of a central uplift during the modification stage. The final structure contains deep rocks thrust up to form a mountain range in the crater center, surrounded by a flat plain and a terraced rim produced by inward movement along stepped normal faults. * The transition between simple and complex craters depends largely on the size of the planetary body * Comparing rocky bodies of various sizes the transition will occur at smaller crater diameters as planetary gravity increases

Answer 46

Four classifications of craters * Crater morphology changes as size (diameter) increases: * Simple craters (bowl-shape) * Central Uplift craters * Peak-ring craters * Multi-ring Basins * The transition size varies with surface gravity and material properties

Answer 47

* Depth/diameter ratio decreases as craters get larger * Gravity on icy satellites similar to that on the Moon * Transition occurs at smaller diameters than for Moon – due to weaker target material? (ice vs. rock)

Answer 48

Probable impact craters may be confirmed through observation of unique deformation effects in rock / minerals Shock metamorphic effects

Answer 49

Impactite is the general term given to any rock affected by one or more hypervelocity impact events →applies to both terrestrial and extraterrestrial rocks

Answer 50

* Secondary craters are formed by the impact of rocks ejected from primary impact craters * Add to the total crater population * Other complications: target properties can cause variation in size (weak icy target vs. dry rocky target)

Answer 51

Some surfaces reach ‘maximal cratering density’ also called ‘equilibrium density’ meaning that any new crater will obliterate a previous crater craters of a given size are obliterated by impact erosion at the same rate as they are formed

Answer 52

Relative dating using crater density; heavily cratered surfaces are old and sparsely cratered surfaces are young. Old surfaces have a lot of big craters and young surfaces have mostly smaller craters * Uncertainties in cratering rates can result in large uncertainties in age estimates * Relative dating employs other concepts such as the law of superposition, the law of cross-cutting relationships and other principles of stratigraphy

Answer 53

■Closest planet to the Sun (0.387 AU) ■Smallest planet in the Solar System (D = 4,879 km) ■Orbits the Sun once every ~88 Earth days –Highest eccentricity –Smallest axial tilt –Rotation period = 59 Earth days –Length of a “day” (sunrise to sunrise) = 176 Earth days

Answer 54

the plane of Earth’s orbit around the Sun

Answer 55

■the amount an orbit varies from circular

Answer 56

angle between a planet’s rotation axis and the ecliptic

Answer 57

■Highest eccentricity (0.206) ■Smallest axial tilt (0.01°) ■Completes three rotations for every two orbits ■Heavily cratered with more lightly cratered terranes ■No natural satellites ■No substantial atmosphere, but continuously-cycled “exosphere” ■Hydrogen, helium, oxygen, sodium, calcium, potassium, magnesium ■Large Temperature fluctuations (+430 °C to -170 °C) ■No Mercurian meteorites ■4880 Km diameter

Answer 58

■Same range of crater morphologies as the Moon –Simple, complex (central uplift, peak ring), multiring basin –Transition simple → complex occurs at a smaller diameter compared to the Moon –Surface Gravity Mercury (0.38) and the Moon (0.17) (Earth = 1.0) ■Largest crater = Caloris Basin (multiring type) ■Many rayed craters ■“Ghost craters” on the smooth intercrater plains of Mercury are similar to those seen on the Moon and Mars ■Represent impact craters buried by lava flows ■Estimated that flows would have been ~1-2.7 km thick (Head et al., 2008)

Answer 59

■On Mercury the continuous ejecta blanket occurs within 0.5 crater diameter; on the Moon deposition occurs 0.7-1 crater diameter ■Paradoxically Mercury has spectacular rayed craters, with one measured crater ray extending \>4500 km ■Longest ray on the Moon from Tycho is ~2,000 km ■Interpretation: mercurian rayed craters are less degraded and therefore younger or “space weathering” effects are less efficient on Mercury ■Impact craters range in size from the spatial resolution limit of MESSENGER (10s of meters) to 1,560 km (Borealis Basin) ■ There is an impact crater Pantheon Fossae informally called The Spider with “Spokes” radial to the center of the basin –Not related to Apollodorus crater –Volcanic activity? Grooved valleys probably are extensional faults from doming (magma intrusion at depth)

Answer 60

■Density of the terrestrial planets (g/cm3) –Mercury = 5.4 –Venus = 5.2 –Earth = 5.5 –Mars = 3.9 ■Mercury has a large iron core relative to the size of the planet which makes it so dense ■Core radius 1800 km, mantle 600 km thick, crust 100-200 km thick ■Core structure: solid-liquid-solid? ■Why is Mercury so different (denser + metal-rich) from other terrestrial planets? ■Three leading hypothesis 1. Large impact hypothesis: impacted by a large a planetesimal after differentiation, stripping away much of the outer silicate crust Prediction: Al- and Ca-depleted 2. Timing of formation: tremendous heat in the early nebula vaporized part of the outer rock layer of proto-Mercury, leaving the planet strongly depleted in volatiles Prediction: depletion in easily volatile elements (K and Na) 3. Mechanical sorting of silicate and metal grains in the solar nebula with lighter silicate grains preferentially lost to the Sun; Mercury formed from this metal-rich region Prediction: no change in silicate composition, just the relative proportions of metal and rock

Answer 61

■One of the major discoveries of the Mariner 10 flybys was that Mercury possesses an internal magnetic field –1% strength of Earth’s –Active or remnant magnetic field? Debated until MESSENGER which confirmed a magnetic field –Similar in its “dipole” shape to Earth’s magnetic field which resembles the field produced by a giant bar magnet at the center of the planet - The south pole is more exposed to charged particles

Answer 62

■Mercury, the Moon and other planetary bodies which lack an atmosphere could not have supported surface processes related to wind or liquid water ■Subject to “space weathering” ■Bombardment of airless bodies by the solar wind and cosmic rays

Answer 63

* S/V decreases with increasing values of planetary radii; these ratios are qualitatively related to cooling rate because the amount of heat lost by radiation depends on its surface area relative to its volume * Mercury’s interior is still hot, but its lithosphere is thick, preventing decompression melting and magma from reaching the surface

Answer 64

■Volcanism definitively identified by MESSENGER by distinctive features such as lava flows, shield volcanoes and volcanic vents

Answer 65

■Elemental abundances in regolith (top 1 mm) of planetary bodies lacking an atmosphere measured through planetary X-ray florescence (XRF) –Solar X-rays excite atoms at the planet’s surface causing them to emit characteristic X-rays –Detected by MESSENGER X-ray Spectrometer ■Compared to Earth and the Moon Mercury is enriched in Mg and Si and depleted in Al, Ca and Fe ■Intermediate in composition between komatiites and typical basalts

Answer 66

■Prominent features on Mercury is the presence of unusual lobate scarps ■Dominant tectonic landforms on Mercury are the scarps and ridges (called rupes) of various shapes (arcuate, lobate and linear forms) ■100 – 100 km length, rising \>2 km above surrounding plain ■Mapping suggest crustal shortening ■Interpretation: thrust fault movement resulting from compressional deformation

Answer 67

* There is ice despite equator temperature of 450^oC * Due to Mercury’s axial tilt (0.01o), the floors of polar impact craters never “see” sunlight can get as cold as - 223^oC * Mysterious hollows which are fresh-appearing, irregular, shallow and rimless depressions - May be still forming today * Most likely formation: recent loss of volatiles through sublimation, space weathering, outgassing or pyroclastic volcanism * High K/Th measured by MESSENGER rule out timing of formation * Mercury surprisingly abundant in volatile elements that evaporate at moderately high-T Carbon

Answer 68

Listed as an outcome but cannot find an answer to this question

Answer 69

■Lobate scarps formed by thrust faulting –Reflect global contraction due to cooling and therefore shrinkage of the planet’s interior ■Data from Mariner 10 –Horizontal shortening 0.3-3.2 km resulted in a decrease in radius of 1 to 2 km (Watters et al. (1998) Topography of lobate scarps on Mercury: New constraints on the planet’s contraction. Geology 26, 991-994) ■New data from MESSENGER –New census of lobate scarps found many more with steeper faces –Found other features “wrinkle ridges” that are less pronounced but also attributed to contraction - Significant horizontal shortening and shrinkage of 4.7-7.1 km depending on assumed dip angles

Answer 70

■Brightest planet in sky ■Diameter (12,104 km), mass (5.2 g/ms3) and gravity (8.87 m/s2) nearly the same as Earth’s ■Rotates once every 243 days, retrograde orbit (backward rotation) ■Orbit lasts 226 days ■Axis of rotation is 177.4° (north pole is down) ■Thick atmosphere 97% CO2 ■No magnetic field ■Surface T ~480 °C ■Surface P ~95 bars ■Naming: on Venus, all features are named after women, dead at least three years, who have done something important or deserve it (controlled by IAU)

Answer 71

mountain-like features

Answer 72

large areas, tends to be higher than surrounding terrain

Answer 73

Planitia: low-lying areas

Answer 74

highly-fractured regions

Answer 75

■Radio Detection and Ranging ■Signal sent out from satellite and bounced off surface –Return time and strength determine distance from source and surface roughness ■For images from Venus, rougher surfaces represented as white

Answer 76

■Similar size, mass and density to earth; formed in the same general area of the solar nebula therefore bulk composition similar to earth (core / mantle / crust) –Solid core or partially molten? No intrinsic magnetic field –Two top hypotheses: Venus rotates too slowly to get convection started or thermally-driven convection is prevented, or both

Answer 77

■lowland ■uplands ■highlands

Answer 78

Lowlands are relatively smooth with elevations less than 0 km with local relief less than 1000 m ■Some basins are ~2 km deep ■Structural basins (not impact-related) formed by downward bending of the lithosphere ■Tectonic features – strongly deformed belts of sinuous ridges similar to mountain belts on earth –Compressional deformation ■Similar to Moon’s Maria and martian planitia but much younger

Answer 79

Uplands are transitional between lowlands and highlands, between 0 km and 2 km elevation ■Dominantly extensional tectonic features – long fracture belts, troughs and rifts ■Some rises are broad domes capped by rifts and shield volcanoes ■Many volcanoes have a summit caldera ■Other volcanic features: low-relief calderas, fissure-fed lavas ■Ring-like coronae (later)

Answer 80

The highlands on Venus consist of two continent-size and several smaller ones rise above the uplands with elevations between 3 to 5 km; complexly deformed by tectonic processes with few volcanoes, cover \<15% of surface ■Flat plateaus with mountainous regions containing peaks as high as 11.5 km ■Resemble mountain belts on lowlands – sinuous valleys and ridges – but are much higher –Compressional stresses ■Related to extensive crustal thickening over mantle down-welling which pulls crustal material together?

Answer 81

■Lower density of craters on Venus than moon or Mercury ■Uniform distribution of large craters ■All surface is same age: \<750 Ma ■Some impacts have lava flows associated with them –Impact raises the T of the rocks from surface T –On Venus, surface T is ~480°C, so additional heat may melt the rocks ■190 confirmed impact craters on Earth; and ~1000 on Venus, yet the surface of Venus is thought to be very young This is because over 70% of the Earth's surface is water

Answer 82

* No linear chains of volcanoes on Venus, or stratovolcanoes aligned along deep trenches; * can conclude that Venus does not have an active system of plate tectonics → use hot spot tectonics to explain volcanic systems on Venus * Different scales of melting and convection are probably responsible for the formation of features associated with hot spots on Venus * Volcanoes on Venus are not arranged in linear arrays like on Earth but also do not occur at random * Volcanoes are more common in uplands than on lowlands or highlands * lava flows extend for 100s of kilometers from the summit suggesting a composition that has a low viscosity

Answer 83

* Venus does not have an active system of plate tectonics → use hot spot tectonics to explain volcanic systems on Venus * Single plate planet (lacks plate tectonics like on Earth) * Mantle convection dominated by plumes and anti-plumes * Upwelling underlies the rifted, volcano-capped domes and regions rich in volcanic features * Mantle down-welling underlies lowland plains and deformed highland plateaus where crustal thickening has been causing by extreme down-welling

Answer 84

Distinctive volcano-tectonic features consisting of a nearly circular chains of rugged mountain belts created by faulting and fracturing surrounding a central plain or dome (100-1000 km across) ■Formation of coronae may involve several steps 1. Rise of a mantle plume; heat and buoyancy uplift crust resulting in radial fracturing and volcanism 2. The large plume head flattens and spreads out along the base of the strong lithosphere, transforming the dome (A) into a central plateau 3. The plume cools and contracts

Answer 85

■Orbit of Venus is ~0.7 AU ■96.5% CO2, and 3.5% N2; also SO2, CO, H2O, H2S, noble gasses (He, Ne, Ar, Kr) ■CO2 helps drive a runaway greenhouse effect (surface T ~480 °C) ■Atmospheric circulation on Venus is much more rapid than rotation of the planet itself → in the upper layers wind speeds reach 350 km/hr, moving in the same retrograde motion as the planet * Wind speeds decrease to 5 km/hr at surface * Equalized surface temperature of Venus ■Venusian clouds are small droplets of H2SO4 * Droplets evaporate before they hit the ground * Atmospheric pressure at the ground is ~90-95 bars ■High as pressure in the oceans at a depth of 1000 m

Answer 86

* High surface temperature + high concentration of CO2 + absence of water on Venus → evolution gone wrong * Assumptions: Earth and Venus formed in the same vicinity of the solar nebular – starting materials similar after accretion * Both planets differentiated into core-silicate mantle-crust * Volatiles in planetesimals released by heating, forming a dense atmosphere composed mostly of H2O vapor, CO2 , CH4 and N2 (+ minor noble gases, NH3)

Answer 87

■At the end of accretion, the atmospheres of Earth & Venus were probably very similar ■An important reaction: CH4 + O2 →CO2 + 2H2 ■After magma ocean crystallization the anorthositic crust insulated the atmosphere from earth’s hot interior ■Temperature drops → water vapor condenses!! * CO2 dissolves in water ■This is where the atmospheric evolution of Earth and Venus diverge * Temperatures too high for condensation on Venus * Even if condensation occurred the resulting decrease of global temperature was not sufficient to prevent water from re-evaporating * Venus receives more solar radiation than Earth (645 W/m2) vs. (342 W/m2)

Answer 88

■None on surface, very little in atmosphere (100 ppm in atmosphere) ■Assumed that Venus received same amount of water from planetesimals and comets as the Earth ■Several hypotheses: * The bulk of Venus is inherently water-poor, but not carbon-poor * Venus contained water that outgassed; however, the water never condensed to form a liquid because of high atmospheric temperatures * Water vapour outgassed, condensed to a liquid which flowed across and shaped the landscape but then disappeared and all ancient landscapes were subsequently destroyed

Answer 89

■Weathering on Venus very different from Mars or Earth –Differences: absence of water, extreme temperatures and pressures, and composition of the atmosphere ■Weathering rates low because of lack of running water –Provide the small particles which are moved by the wind ■Winds on Venus play an important role in the geologic evolution of surface features –Streaks, yardangs and dunes

Answer 90

■D = 3,476 km ■Locked in synchronous rotation with the earth (1 : 1 spin : orbit) –“near-side” and “far-side” ■Lacks an atmosphere ■No evidence of past running water on surface ■Rock type: anorthositic crust with basaltic mare ■Core is small (~20% of size)

Answer 91

–Mountainous highlands composed of plutonic rocks (gabbro to anorthosite) composed of high albedo plagioclase feldspar ■Plagioclase feldspar –CaAl2Si2O8 (anorthite) ■Represents the original lunar crust formed by crystallization of a magma ocean ■Crater density of the highlands is much higher than basalt plains (maria) ■Lunar far side consists largely of heavily cratered highlands composed of anorthositic gabbro

Answer 92

–Basaltic lava that filled giant impact basins ■Major minerals: plagioclase feldspar, pyroxene ± olivine –No amphibole or phyllosilicates ■Subdivisions: high-Ti and low-Ti basalts, also KREEP basalts (more on this later) ■Originate from partially melted areas of the Moon’s mantle (100–400 km depth) ■Radiometric ages of Apollo maria samples (3.16 - 4.2 Ga) ■Mare basalts have high (\>16 wt%) FeO, low to moderate mg and usually high TiO2 and low Al2O3 ■Various subclasses of mare based on diverse bulk TiO2 contents * \<1.5 wt% TiO2 - VLT (very-low titanium) * 1.5 - LT (low-titanium) - Medium titanium * \>6 wt% TiO2 - HT (high titanium)

Answer 93

■Crater diameter ranges from 1 m to \>1000 km ■Simple → complex → multi-ring basins ■Rayed craters with extensive ejecta blankets

Answer 94

–Impact ejecta blankets the Moon, composed of boulder-size material to fine-grained pulverized rocks and small glass beads (agglutinates) by micrometeorite impact melting ■Moon’s surface covered by a layer of unconsolidated debris called regolith – 5 m to 10 m thick ■Density ~1.5 g/cm3 ■Pulverized mineral / rock shards (50% by weight has a grain size between 0.06 – 0.08 mm) ■Exposed to micrometeorite bombardment and solar wind irradiation –Agglutinates, implants H & He

Answer 95

One of the objectives from the slides but can't find the answer on powerpoint 8 - Luna

Answer 96

–Impact ejecta that blanket the Moon, composed of boulder-size material to fine-grained pulverized rocks and small glass beads (agglutinates) by micrometeorite impact melting - Exposed to micrometeorite bombardment and solar wind irradiation NOT SURE IF THIS IS THE CORRECT ANSWER OR NOT

Answer 97

1 - the evolution of the magma ocean by fractional crystallization 2 - simultaneous impact brecciation of the crust (megaregolith and regolith) 3 - later partial melting of the mantle and the formation of chemically distinct basaltic lava flows due to mineralogical zoning of the mantle

Answer 98

■Volcanism on the Moon differs in many ways from that on Earth –Age –Setting (Earth = volcanic occur mainly within line linear mountain chains / mare are circular in shape, controlled by surface elevation and crustal thickness) –Physical differences (lunar gravity is 1/6 that of Earth’s, low mare viscosity, “dry” magma / lava) ■Vast lava plains that infill large impact basins –Floor Fractured Craters (FFCs) ■Sinuous rilles ■Dark mantling deposits ■Domes and cones

Answer 99

the lunar crust is thinner on the near side compared to the far side. Fractures allow magma to reach the surface preferentially where it is thinner. The moon has a small iron-rich core (20% of radius) encircled by a partially molten layer. The Moon’s center of mass (CM) is offset by 2 km from its center of figure (CF), so an equipotential surface, which experiences an equal gravitational force at all points lies closer to the lunar surface on the near side

Answer 100

■Resemble river valleys but lunar rilles usually flow away from small pit structures ■Mark lava channels and / or collapsed lava tubes ■Lava flows could also have cut down into older rocks

Answer 101

Small-scale explosive lunar volcanism forming pyroclastic cones

Answer 102

■No evidence for plate tectonics – one plate planet (like Venus, Mercury) –Extensional stresses found on outer margins of mare basalt deposits (grabens) → dense mare basalt weighs down crust resulting in compression in central portions (wrinkle ridges) ■Also see evidence for contraction of the moon by 182 m since it’s formation –Evidence: lobate scarps (compressive stress) –Most tectonic features are associated with crustal adjustments in response to large impacts or mare deposits within basins

Answer 103

■The origin of the Moon must explain three main observations: –Depletion of the Moon in volatile elements relative to carbonaceous chondrites (K, Na, F, Zn + 19 others) –Depletion of iron in the Moon as indicated by its low bulk density (3.344 g/cm3) compared to the bulk density of Earth (5.520 g/cm3) –The absence of water (hydrated minerals) in the igneous rocks of the Moon ■Other oddities include the large size of the Moon relative to the Earth and the energy of the system –Largest satellite in the solar system relative to its planet: ¼ the diameter –Unusually high angular momentum compared to the other planet-moon systems ■Prior to return of lunar rocks from Apollo (1969) and subsequent geochemical investigations, three hypothesis were considered 1. Fission Hypothesis: the moon was once part of the earth and somehow separated from the Earth; the present Pacific Ocean basin is the most popular site for the part of the Earth from which the Moon came * Disproved by exploration of earth’s ocean basins 2. Capture Hypothesis: The Moon was formed somewhere else and was later captured by the gravitational field of the Earth * Disproved by geochemical similarity between Moon-Earth (next slide) 3. Condensation Hypothesis: The Moon and the Earth condensed together from the solar nebula * Doesn’t explain density issue or why the Moon lacks water ■Geochemical analysis of lunar rocks show identical oxygen isotope ratios to terrestrial rocks, indicating that they originated from the same material ■A common origin for the Moon and Earth is required by their identical isotopic composition THIS ALL LEAD to the giant impact hypothesis ■Simulations of the current giant impact hypothesis continue to refine the details

Answer 104

■No hydroxyl (OH-) bearing minerals like biotite, muscovite, amphiboles, serpentine, clays ■Lack of water is important in determining the Moon’s origin (previous slides) ■Evidence for water ice in deep impact basins which are permanently shaded –Small amounts mixed with regolith at poles –Evidence for larger buried (40 cm depth) water-ice deposits at poles –Primordial (accretion) versus recent (comet impacts)?

Answer 105

1. The Moon is not a primordial object; it is an evolved terrestrial planet with internal zoning similar to that of Earth 2. The Moon is ancient and still preserved an early history (the first billion years) that must be common to all terrestrial planets 3. The youngest Lunar rocks are virtually as old as the oldest rocks on Earth 4. The Moon and Earth are genetically related and formed from different proportions of a common reservoir of materials 5. The Moon is lifeless; it contains no living organisms, fossils or native organic compounds 6. All Moon rocks originated through high-temperature processes with little or no involvement with water; they are roughly divisible into three types; basalts, anorthosites and breccias 7. Early in its history, the Moon was melted to great depths to form a “magma ocean”’ the lunar highlands contain the remnants of the early, low density rocks that floated to the surface of the magma ocean 8. The lunar magma ocean was followed by a series of huge asteroid impacts that created basins which were later filled by lava flows 9. The Moon is slightly asymmetrical, possibly as a consequence of its evolution under Earth’s gravitational influence; the crust is thicker on the “far side” while most volcanic basins occurs on the near side 10. The surface of the Moon is covered by a rubble pile of rock fragments and dust, called the lunar regolith, that contains a unique radiation history of the Sun

Answer 106

■Orbit 686 days ■Radius = 3396 km (D = 6792 km), core radius = 1480 km ■Differentiated planet with an iron sulfide core –14-17% sulfur, twice the concentration of lighter elements than Earth’s core ■Crust is 20-80 km thick ■Less dense than Earth –(3.9 g/cm3 vs. 5.5 g/cm3) ■Most common rock type = Basalt –Some silica-rich terrains ■Dusty (iron oxides) ■Axial tilt = 25° –Seasons like on Earth! ■“wobble” leads to ice ages 50-100 Ma ■Thin atmosphere: 95.97% CO2, with minor amounts of N2 (1.89%), O2 (0.146%), Ar, CO, H2O –Average surface pressure = 6.5 mbar –Same pressure 40 km above earth’s surface! ■Temperature range -133 °C to +27 °C (avg surface T = -63 °C)

Answer 107

■Two moons thought to represent captured main-belt asteroids (carbonaceous chondrites) ■Phobos –Orbits Mars in 7.5 hours –Orbital radius is decreasing –D (avg) = 24 km –Density, ρ = 2.2 g/cm3 ■Deimos –Orbits Mars in 30.3 hours –D = 12.4 km –ρ = 1.7 g/cm3

Answer 108

■Similarities: evidence of processes related to running water, glaciers, wind, volcanism and tectonic deformation (plate tectonics in the past?) ■Differences: Mars preserves an extensive part of its ancient heavily cratered crust, atmosphere thin (low atm pressure) and CO2-rich

Answer 109

–Volcanism can produce circular features –Abundant secondary craters –Highly modified surface (wind, water, glacial erosion) –No calibration for crater counts

Answer 110

■Fundamental feature of Mars expressed by a physiogeographic and geological divide between the heavily cratered southern highlands and relatively smooth plains of the northern lowlands –Also dichotomous with respect to. magnetization (and crustal thickness ■Origin? –Endogenic Models ■Mantle convection, plate tectonics or early mantle overturn –Exogenic Models ■Giant impact or multiple giant impacts impact of a Pluto-size body which collided with Mars early in its history. Erases the cratering record of half the planet leaving behind the low-lying, flat volcanic plains of the northern lowlands

Answer 111

■Vertical component of magnetic fields originating from the martian crust –Strength of magnetic field low in northern lowlands, Tharsis and deep impact basins but high in part of the ancient martian crust

Answer 112

■Topography of the northern physiographic province is dominated by the Tharsis plateau and the low plains that merge northwards into the Vastitas Borealis –Tharsis Plateau * the main plateau rises 7 km above zero-elevation; highest points are the summits of Ascraeus, Pavonis and Arsia Mons, with the largest mountain = Olympus Mons * Straddles equator * Few impact craters (\<3.8 Ga) ■Olympus Mons * Build-up of Tharsis attributed to the presence of a large plume at the base of the underlying lithosphere; formation of basaltic magma by decompression melting of the mantle ■Young Lava Flows * Low abundance of impact craters on some lava flows of Olympus Mons and on other volcanoes tells us that these flows are not very old * Crater counts to indicate “exposure ages” of lava flows * Some as young as 10 Ma (needs to be confirmed by isotopic dating) * Information from the age of martian meteorites * Young basalts called shergottites are 154 – 474 Ma ■Valles Marineris * Canyon system formed as rift valleys from crustal extension related to uplift from Tharsis Plateau vs. Grand Canyon on earth eroded by down cutting of the Colorado River * Extends from Noctis Labyrinthus in west to Capri Chasma (~3500 km long) * 9 km of total relief * 120–600 km wide! * Although Valles Marineris originated by tectonic processes it has been modified by landslides of steep rims which over time have caused the canyons to become wider and shallower –Utopia Planitia * Landing site of Viking 2 (1976 lander) * Major findings: thin coating of water ice on rocks / regolith * Chemical analyses of “soil” * Suggests minerals like clay (nontronite), iron oxides (hematite and goethite), sulfates (MgSO4 and CaSO4) and halites (NaCl and KCl)

Answer 113

■Compared to the northern hemisphere the southern hemisphere is mountainous and cratered (more similar to lunar highlands) ■Large impact basins –Hellas Impact Basin (Hellas Planitia) * D = 1700 km; lowest point lies 8.2 km below surrounding highlands * Removed 186,000,000 km3 of rocks but surrounding plain is not mountainous and don’t see a raised rim * Scarcity of craters within Hellas Planitia * Rocks underlying Hellas are not magnetized * Timing: Hellas impact occurred after the magnetic field had collapsed but before significant climate cooling * Dao and Niger are a pair of canyons extending through highlands to eastern Hellas region * Classification: Outflow Channels * Large, sudden erosional features formed by release of enormous volumes of water - Isidis Planitia and Syrtis Major * D = 1200 km impact basin with a smooth * uncratered floor ~3.5 km below zero-elevation contour * NE rim eroded and buried by sediment ■Floors are sparsely-cratered (covered by layers of sediment deposited by water / wind) * Volcanoes * Syrtis Major Volcano, Hesperia Planum, Hadriaca Patera * Volcanic centers are much younger than the highlands themselves

Answer 114

■Most central volcanoes include shields, domes, highland patera, and ridge features: * Shields = attributes of classic Hawaiian shield volcanoes composed of successive flows of low viscosity basaltic lava emplaced by lava tubes and channels erupted from central vents / calderas / parasitic cones * Domes have flank slopes steeper than shields inferred to represent eruption of higher viscosity silicic lavas ■Most central volcanoes include shields, domes, highland patera, and ridge features: * Highland Patera are low-profile volcanoes with calderas, radial flows and channels = oldest volcanic constructs on Mars (\>3.9 Ga) * Alba Patera is a unique, very low profile feature in Tharsis Plateau with radial lava flows extending 400 km from central caldera! * Ultramafic flows? Covers 1.13 x 106 km2 (more than all martian shields combined!) * Ridged Plains are similar to tectonic ridges on Mercury, Moon, but on Mars are thought to represent deformed thick basalt flows

Answer 115

■Streaks on martian surface attributed to a network of wind vortices called “dust devils” on mars * Spinning columns of rising air heated by warm daytime temperatures during the martian summer ■Sand dunes provide Insight into atmospheric processes * Downwind faces shaped by sand avalanches, making them steeper than upwind faces * Ripple size is related to the density of the fluid moving the grains (atmosphere) * Dark color = dark minerals (basaltic) THIS IS IN THE MIDDLE OF THE SLIDES ON WATER ON MARS so not sure if it should be under evidence for water on mars or not it seems like it has nothing to do with water when I read it but I am not sitting in class you are so you would know

Answer 116

Nothing in the powerpoint presentation but is an outcome of that lecture

Answer 117

1. Many features related to running water * Dendritic valley networks attributed to precipitation and running water in the Noachian * clays found in Noachian aged terrains, clays only form in the presence of water so their widespread distribution indicates there was potentially significant liquid water in Mars’ past * Fluvial morphologies in more recent terrains seem to originate from groundwater * Valleys appear suddenly 2. Conglomerates are sedimentary rocks that form by deposition from running water * Noachian-Hesperian transition 3. Past climatic conditions that contrast with the modern martian environment (not sure if 4 or 5 are evidence or if they are random slides she added about Mars after the water part - not clear) 4. Sedimentary rocks including sandstone, conglomerate, mudstone and shale have been imaged and analyzed on the Martian surface by NASA rovers 5. Presence of Hematite spherules * Number of hypotheses proposed for their formation: * Concretions * Impact spherules 6. Mars has distinct polar caps but also belts of glaciers at central latitudes * Amount of water equivalent to Mars covered by 1.1 m of ice! * CO2 versus H2O? * Radar measurements from MRO are consistent with water ice 7. Dark streaks on steep slopes (called recurring slope lineae) * Appear and lengthen at mid-latitudes and in equatorial regions when steep slopes face the sun

Answer 118

■Size range from 1800 km (Hellas) to \<1 m depressions ■Same progression from simple -\> complex -\> basin as the Moon but morphological transitions occur at smaller diameters on Mars * Major difference from Lunar, Mercurian and Venusian craters: ejecta deposits exhibit flow-like patterns formed by impact in wet terrain or permafrost regions melted by impact

Midterm Flashcards

(147 cards)