Test 2 Flashcards
What is nucleosynthesis?
process that creates new atomic nuclei from pre-existing nucleons, primarily protons and neutrons
Tell me about the Big Bang Nucleosynthesis?
-90% of the universe is composed of H and He
-Almost all H, He were created in the first 3 min after Big Bang
-universe cooled enough for H atoms to form, then fuse to form HE
-H + H =H2
-H2 + H2 = He
-Process ended after ~ 20 minutes (cooled and density decreased as early universe expanded
-Earliest nebulae composed of 3/4 H and 1/4 He (no stars yet)
Review: what’s a Nebulae?
patchy cloud of gases and dust
what was the periodic table right after the Big Bang?
H, He, Li ,Be
Stellar Nucleosynthesis, tell me about it?
-started; 500 may after B.B
-larger atoms made from smaller under high heat and pressure
-nuclear fusion and fission
during stellar nucleosynthesis, atoms gets released from a star, explain it…
-it happens during its lifetime via the stella wind
-as it dies, samll and medium starts become red giants, large stars become supernova explosions
-all elements starting with C produced this way
-stars are element factories
Triple-alpha process is an example of what?
2 Helium atoms forming Be,
Be + He = C
What is cosmochemistry?
study of chemical composition of matter in the universe and the processes that led to those compositions.
Natural samples: meteorties, asteroids, comets, returned samples
Remote spectroscopy: planets, stars, nebulae
Numerical modeling
what is a meteorite?
An extraterrestrial rock that survives an impact on the Earth
what’s the development of cosmochemistry in 20th century? (3)
1- invention of isotope mass spectrometer measure isotope ratios
2-apollo program and state-of-the art analytical facilities to anylyse lunar samples
3-allende carbonaceous chondrite meteorite
what is the Hourglass Nebula?
a young planetary nebula
where do meteorites come from?
material that is as old as S.S and provides scientists with a record from the early solar nebula
what are carbonaceous chondrites?
stony meteorites that have retained many of their chemical properties since their formation 4.56 billion yeas ago
why are carbonaceous chondrites important?
major focus of cosmochemical investigations
what’s a prime example of carbonaceous chondrite?
Allende meteorite
what do the most primitive meteorites contain?
small amount of presolar grains (older than S.S) coming from supernovae
what are the most abundant elements in the earth’s crust?
Si + O
what are 5 silicate mineral examples?
-feldspar
-quartz
-olivine
-Mica
-Pyroxene
who completed the first crewed trip behind the far side of the Moon?
Apollo 8, dec 1968
What were some early ideas about the Moon?
Plutarch:
-Moon had deep recesses; shadows of rivers or deep chasms
-entertained the possibility that the Moon was inhabited
Was the Moon highly reflective which if so, meant what?
according to William Gilbert
yes and it meant covered in oceans
Earlier science ideas:
what was the 3 hypothesis?
1- Fission; early Earth spun so fast it spun off the moon when it was still molten (Darwin)
2-Capture; Moon formed somewhere else in solar system where there was little iron, then captured into orbit around earth by gravity
3-Coaccretion; Moon is a sister world that formed in orbit around Earth at the same time
What was pre-Apollo knowledge?
-Moon density = 3.3 g/cm^3
-Close to Earth’s mantle
-Moon is fluffy, loose dusty
what does Maria mean towards the Moon?
seas in latin.
Smooth, low-lying plains
-few craters (younger)
what does Highlands mean towards the Moon?
Higher elevation
Numerous craters (older)
what are the 2 In situ experiments in Apollo science?
1-Laser ranging reflectors for distance of Earth-Moon
2-Seismometers for internal structure of Moon and Moonquakes
what did the Apollo science bring back from the Moon?
samples of rocks and soil
what’s the total mass that we’ve extracted from the Moon and brought back to study?
383 kg
What are Mare Basalts?
-fine-grained, dark coloured volcanic rocks
-3.2-3.9 Ga
-Low iron, low volatiles
what are Highland Anorthosites?
-Coarse-grained, light coloured, plagioclase feldspar-rich plutonic rock
-4-4.4 Ga
-Low iron, low volatiles
what are Impact breccias?
-Heterogeneous, irrefular sized and shaoed fragments of other rocks
-Majority of Apollo samples are breccia so important on the Moon
what is regolith?
-loose soil
-created by slow meteoritic bombardment (impacts)
-Over time, material is mixed vertically and horizontally by impact processes
during fractional crystallization, which crystalise first during magma ocean and crust formation?
inside completely molten magma, olivine and pyroxene then plagioclase feldspar floats and makes crust
what are the 3 steps in the formation of Maria?
1-impact
2-ring mountains and melt
3-mare filled with lava
which of the 3 early science hypothesis failed ?
all of them
-Fission: because total angular momentum proved it could not form that way
-Capture; lunar rocks showed same isotope composition as the earth
-coaccretion; could not explain the Moon’s lack of iron
what is the giant impact hypothesis?
another smaller pla netary body, The, hit earth in its growth process, blowing out rocky debris.
Fraction of that debris went into orbit around Earth and aggregated into the Moon
what’s the problem with the giant impact hypothesis (old version)?
Moon should be made mostly of Theia material but it shows more isotopic ratios of those on earth
what is identical between the Moon and earth?
oxygen isotope ratios
what else supports the Giant impact hypothesis?
-Earth spin and Moon orbit in same direction
-Magma ocean on Moon difficult to form by accretion; possible with giant ..
-Moon depleted in volatile elements
-Giant impact is consistent with Nebular Hypothesis
-Large collisions in other star systems give debris disks as well
what’s the new version of the giant impact hypothesis?
Theia vaporized and rotates synestia instead of impact then center cools to form earth and the outer remnants form Moon.
what are tectonics?
large scale structure and deformation of a planet’s crust
on Earth we have … tectonics:
plate tectonics
what are the differential stresses of tectonics?
-compressive forces (folding and faulting)
-Tensional forces (stretching and thinning, faulting)
-Shearing forces ( shearing and faulting)
what do all the differential stresses have in common?
faulting for each scenario
what is hot spot volcanism?
when there’s a mantle plume and it drives through the oceanic lithospheric crust and pops out
have planets cooled down or heated up since their formation?
cool down
what do plate tectonics require on Earth?
1-mantle convection = engine
2-cool rigid crust = allows for plates (lithosphere)
3-water =lubricates and allows partial melting
is mercury and the Moon tectonically active?
not anymore
how long has the moon been inactive ?
3 billion years
NWA 773, what is it? how old is it?
lunar meteorite containing a large piece of olivine gabbros rock
2.865 billion years old
what does the light gray part of the meteorite NWA 773 mean?
an impact breccia made of tiny fragments of other rock
what is the youngest lunar rock known?
NWA 773
how long has Mercury been inactive?
3.7-3.9 Ga
does mercury have hints of past tectonics? if so, what are they?
yes,
-faults and ridges suggest compressive forces
-suggesting that mercury contracted slightly as it cooled