Astro 150 Midterm – Flashcards
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Age of Solar System
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~ 4.5 Byrs
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Unit for distance
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1 astronomical unit 1.0 AU distance from the sun
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The size of worlds in our solar system
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are 1,000s of km across. 10 km is the size of most cities, also the size of astroid that killed dinosaurs. Human scale: < 1 km.
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Density
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Mass ÷ volume. g/cm³ density is measured relative to water. water has a density of 1 g/cm³.
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Most common solid materials in periodic table
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ices (H, C, N, O), rocks, and iron
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Density of Water
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1.0 g/cm³
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Density of Rocks
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~3 g/cm³
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Density of Iron
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7.9 g/cm³
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Nothing is much denser than ___ in the solar system.
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5 g/cm³
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Density of Mercury
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5.4 g/cm³ made up of iron and rock. Desist world in solar system.
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Density of Enceladus
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1.6 g/cm³ made up of mostly ice and a little rock.
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Moment of Inertia Factor [K]
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K= how much force you need in order to make an object spin. Is a ratio, has no units.
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Moment of inertia of a uniform sphere
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K = 0.40
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Moment of inertia of a sphere with concentrated center mass of × 2
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K = 0.35
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Moment of inertia of a sphere with concentrated center mass of × 4
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K = 0.32
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Albedo
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The percentage of sunlight that reflects off a surface. The higher Albedo = brighter object, more light reflected off. Changes relatively quickly through time.
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Albedo of a piece of notebook paper
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A ~ 0.6
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Phases of matter
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Solid, liquid, or gas
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Phases of matter depends on
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temperature and atmospheric pressure. No atmosphere = no pressure.
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Temperature is measured in
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Centigrade.
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The higher you go vertically...
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Pressure gets less.
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The lower you go vertically...
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Pressure goes up tremendously.
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Surface of earth (sea level)
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1 atm, 20 centigrade (70 F).
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Density of the moon
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3.34 g/cm³ mostly rock, very little iron
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albedo of the moon
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0.11 dark rock
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Moment of inertia of the moon
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0.393 almost homogeneous.
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size of the moon
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27% of earth's
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mass of the moon
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1.2% of earth's
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gravity of the moon
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1/6 earth
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Mare
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dark, smooth, low albedo, few craters, young, lava flow bits of the moon.
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Highlands
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light, high albedo, many craters, old, impact bits of the moon. (They are not evenly distributed)
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What shaped the moon?
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Impacts, formed by an explosion. Energy comes from the movement of the object.
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Impact Processes
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Exogenetic Source- originating external energy. Kinetic Energy- ½ × mass × velocity²
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Why are all craters on the moon circular?
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They are not caused by an object hitting the moon, but by an explosion once the object hits. Object that caused the crater is vaporized and dispersed.
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Impact Breccia
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Rock composed of broken fragments of minerals, rocks, or even other pieces of Breccia.
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Simple Impact Craters
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<10 km. Craters can be all sizes, even smaller than a human hair (caused by impacts of sand grains).
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During impact explosion
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The material in the explosion only ends up on the rim of the crater. Rocks originally at surface is thrown the farthest. The lower down, the higher energy.
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Depth of deepest rocks in crater
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1/10 crater diameter. (100 meter crater in width → material on rim is 10 meters deep)
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Complex impact craters
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10- 100's km, terraced rim (not smooth & slopey), has central peaks.
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Central Peaks
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In complex craters. Like mountains or volcanos, are formed in minutes (unlike mountains on earth), very large explosions cause a bounce back and are brought to the surface.
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Impact Basins
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>100 km The largest craters, caused by very large objects.
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Secondary Craters
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Material is blown out from large impacts at very slow speeds and plow into the surface of the world- cause non-round craters because there is no explosion.
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Rays
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streaks caused by shock waves.
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Ghost Craters
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If the center of a crater is changed or modified.
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Volcanic and Tectonic Processes
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Endogenetic Source- Originating Internally. Energy from radioactive decay of elements.
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Radioactive Decay
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is a one- way process. Amount of heat is always decreasing, material is always cooling off in our solar system.
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Differentiation
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Add heat, heavy materials sink to the middle and lighter materials move to the side.
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Volcanic Processes
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Sinuous Rills, caused by flowing liquid rock.
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Lava Tubes
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Top cools faster than the bottom, forms tubes of lava.
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Viscosity
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How fast everything goes. Water = 1cP Earth Magma = 30,000 cP (ketchup) Lunar Magma = 3,000 cP (maple syrup)
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Lava Flows
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Found in Mare, caused by large lava flows.
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Basalt
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Rock formed from the cooling of lava at or near the surface.
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Tectonic Processes
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Extension- expanding, straight rilles, Compression.
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Wrinkle Ridges
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Surfaces come together and form a positive (sticks up) feature.
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Relative Ages
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Can be based of stratigraphy. Have to overlap & interact to be able to determine which is younger/older. Can be found by counting craters.
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Crater Density
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Number of craters.
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Cumulative Crater Density
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Only count the number of craters (N) larger than a certain size (D). N(10) = the total number of craters equal to or larger than 10 km per million square km.
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Crater Population
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Relative number of different sized craters. Can have same crater density, but different populations.
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Apollo 13
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Did not land on the moon.
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Apollo 12
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Landed November 1969 on western side mare. Spent 2 days- 5 hrs per day exploring.
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Apollo 16
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Only mission to land in highlands. Brought back 0 volcanic rocks, all impact breccia, shaped by impacts not volcanism
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1. Origin of worlds
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4.5 Byrs
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2. Differentiation
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4.5- 4.0 Byrs
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3. Late Heavy Bombardment
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4- 3.8 Byrs
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4. Geological Activity
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3.0- 2.0 Byrs
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5. Big Chill
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Last 2.5- 2.0 Byrs
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Lunar Regolith
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Like flour, covers the moon, erosion is so slow that footprints will last for millions of years.
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Volatility
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A more volatile substance evaporates at a lower temperature than a less volatile (more refractory) one. How much energy it takes to change phase.
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A world that has been heated will be ________ of volatile materials and _______ in refractory materials.
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depleted, enhanced. (Ice melts, rock is left behind)
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Chemical moon system
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lack of volatiles, magma ocean (moon has been heated enough times to be completely molten rock), lack of an iron core, oxygen isotopes like the earth (hydrogen, deuterium, tritium)
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Accretion
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The collisional growth of objects, small objects come together to form larger objects. Tells us universe is built from small to big.
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Co- Accretion
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Planets form from a cloud of dust, growing from small to large particles. How we believe most planet/ satellite systems formed.
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Capture
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The earth and moon both form by accretion, but are formed at different points in the solar system and the moon is captured by gravitational pull of earth. (Our moon was not captured)
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Fission
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Earth forms by accretion, but is formed very hot and spinning fast, fast enough that a blob flies off of it and creates a moon.
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Giant Impact
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The earth formed by accretion, was hit by object the size of Mars, formed into Earth, debris from collision formed the moon.
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Importance of the Moon
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Earth's tilt is stable (responsible for seasons) due to large fast- spinning moon, tides are caused by gravity from the moon.
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Tidal Drag
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Slight tidal bulge on earth pulls the moon in, giving energy to orbit of the moon at expense of orbit of the earth. Moon moves away from earth ~ 4cm per year, earth's rotation loses energy about 2ms/ century.
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Moment of inertia of Mercury
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0.34, has massive iron core.
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Surface Temperature of Mercury
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700 degrees F
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Characteristics of Mercury
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takes a lot of energy to travel to because of gravitational force of the moon, subtle differences between mare & highlands, unequal distribution of mare & highlands, does not have plate tectonics like earth, no ozone layer.
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Caloris Basin
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Mercury. 1550 km (same size as imbrue basin), formed 3.8- 3.9 Byrs.
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Differences between Mercury & The Moon
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The Moon's highland terrain has small, rough patterned bumps that are restricted to one small piece of Mercury, consequence of Mercury's iron core.
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Scarps
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Fault younger than everything else on Mercury, cuts across everything (highlands, lava flows, etc.) due to the iron core. As it cools, it contracts so the surface folds in response to it
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Atmosphere of Mars
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0.006 (Very thin), 100 degree temp change from day to night, changes in pressure are huge, weather is same everywhere, takes little energy.
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Surface Temperature of Mars
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-10 C (day), -50 C (night) like Antarctica in Winter.
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Hellas Basin
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1400 km, 3.8 Byrs
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Olympus Mons
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Mars. Highest mountain in Solar System, shield volcano like big island of Hawaii, About the size of WA state, 30 km high (15 miles), mars' gravity is less than earth- can build mountains higher.
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What is changing mars today
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wind- thin atmosphere, first world where weather is a factor.
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Viking 1 & 2
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Mars, landing spots are big, smooth, flat planes (easy to land on), pieces of basalt-landed on lava flow.
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Mars Soil Composition
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Soil/ rocks all over Mars are the same, everything was covered with venire of soil, same composition across mars.
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Olivine
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very common in volcanic rocks and dissolves very easily in water. Present in Bustef Crater, proving Spirit had not landed in dry lake bed.
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Hematite
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course- grained (Fe₂O₃) typically found in places that can have still- standing water or mineral hot springs. Small "blueberry" spheres, found at landing site of Opportunity.
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Opportunity Landing site
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Hematite, site dominated by sand (looked like desert), Salt abundance increases with depth- all point to evidence the site was once "wet"
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Endeavor Crater
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Found gypsum, only formed in standing water.
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Phoenix Mars Mission
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Landing near north pole, water is sitting at the surface in solid state- ice. Liquid water condensed to side of space craft, detection of perchlorate in water (acts as antifreeze), water is VERY salty
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Gale Crater
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light- looking rock starts to become abundant in clay (typically form from chemical weathering from water deposited in layers) with mineral veins of gypsum material- formed in wet environment.
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When was water sitting on the surface of Mars?
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About 4.2 billion years old, able to determine amount of argon, get rough dates. No real evidence that water has interacted much on global scale. About a billion years after mars was formed water was gone (on global scale)
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Mare surface of Mars
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about 3.8- 3.9 Byrs.
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Surface of Venus
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Albedo = 0.59, bright clouds, Thickest atmosphere in solar system- 92 atm, temperature does not vary- is extremely hot, slowest rotator in solar system, geological activity comparable to earth, very slow wind speeds- 1m per second, dominated by volcanism.
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Coronae
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Big blister that has fractured the surrounding terrain, big plumes of magma under the surface, pushes up to surface, pushes up and descends.
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Impact Craters on Venus
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has tons, aren't very large or very small, typically complex craters, venus has large atmosphere so object must be very big (bigger than house) to punch through atmosphere. Crater Density of whole planet N(10) = 1.4, global age of 0.6 Byrs
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The way Venus loses heat
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Has no plate tectonics, loses heat through shield volcanos. Heat builds up under surface, then hits critical point where whole surface melts, then repeats (turnover hasn't happened in last half Byrs) all older evidence has been wiped out.
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Earth's atmosphere
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dominated by nitrogen & oxygen. Interactions between atmosphere and surface are always changing the planet. CO₂ has been taken out of earth's atmosphere by weathering (carbonic acid is formed and weathers rock) CO₂ is slowly taken out of atmosphere and stored in Limestone. Other CO₂ removal is light, plankton.
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Atmospheric Sources
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Outgassing, Evaporation/ sublimation, comes from melting of rocks and ice on surface.
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Secondary Atmospheres
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gases that come out are water, carbon dioxide, and a bit of nitrogen.
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Greenhouse Gases
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Carbon dioxide and water, absorb and scatter infrared radiation.
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"Greenhouse Effect"
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some of the infrared light is absorbed and re- emitted by the green house gases → warms surface and atmosphere. infrared light doesn't make it to surface b/c its absorbed, a bit makes it to the surface (basalt), absorbs little sunlight & gets hot, then emits infrared light, but can't escape atmosphere to cool the planet.
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Volcanoes & Atmosphere
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source that creates atmospheres. thermal escape; gases moving too fast and leaving atmosphere. interaction with sun; deuterium makes is hard to escape atmosphere.
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Water
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lubricant for plate tectonics, earth's ozone layer stops UV light- prevents water separation.
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Mars Polar Caps
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made mostly of carbon dioxide- dry ice. Seasonal- size changes dramatically.
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Martian Dust Storm
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South pole evaporates from sunshine, CO₂ turns to gas, creating dust storm- makes mars very dark (overcast)
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Impact Craters on Earth
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None on west coast- relatively new surface, all are ghost craters. Both venus and earth lack large impact basins- formed 3.8 Byrs surface is long gone.
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Chicxulub Crater
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complex crater 65 million years old, goes global due to interaction with atmosphere- material gets blown out of earth, then hits earth again- 15 hrs after impact most of earth is on fire. Damage caused by: blocks sun, wipes out lower food chain, extinction event, temperature rises dramatically
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Yarkovsky Effect
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has most uncertainty- have to know very early in advance, don't blow up an asteroid but change it's albedo to push it away from the earth- more light, more push, vice versa.
