M&P FINAL EXAM Flashcards
(111 cards)
1
Q
What exoplanet detection method was there pressure on NASA to use?
A
Direct Imaging
2
Q
Define factors necessary for defining “earth-like”
A
Radius = 0.1 - 2.0 Earth Radii
Mass = 0.001 - 10.0 Earth Masses
Habitable Zone Factors (distance from star, orbit size, stellar stype, terrestrial/jovian)
Whether planets can be earth-like without an atmosphere
Tidal Lock
3
Q
Define the mass & radius factors when defining “earth-like”.
A
Mass & radius => density => composition (solid or liquid)
If it can hold an atmosphere
With orbit size, tells us temperature
4
Q
Define the habitable zone factors when defining “earth-like”.
A
Distances from the star where surface T allows for liquid water
Depends on orbit size & stellar type
Terrestrial or Jovian => mass & radius
Exoplanet detection methods only yield ⅔ measurements: orbit size, mass, & radius
5
Q
Define the atmosphere factors when defining “earth-like”.
A
Protection from a star
Chemical reactions at surface
Greenhouse Effect => higher T
Habitability
Chemical phase cycles
6
Q
Define the tidal lock factors when defining “earth-like”.
A
Asymmetries in planet density => synchronous rotation (more likely if planet is big or orbit is small)
Ratio of near & far side forces = (R + r)^2 / (R - r)^2 = 18% Earth tidal force stronger than sun’s
Consequences: liquid water unlikely (one side water other ice), terminator most habitable region, intense wind storms
7
Q
What are some orbiting tools for finding exoplanets?
A
2003 - 2020 Spitzer IR telescope
- Transit method
- 5/7 TRAPPIST 1 exoplanets
2009 - 2018 Kepler Satellite
- Transit method
- 2,662 confirmed & 2000 candidates
- 2013 50% known exoplanets
- Limited field of view (1/400 of whole sky)
2013 - Present GAIA
- Map stars in 3D & measure brightness variations
- Sees whole sky
- 300 candidates & 2 confirmed
2018 - Present TESS
- Transit method
- Sees whole sky
- 7,525 candidates & 618 confirmed
2021 - Present JWST
- Transit method + spectroscopy for atmosphere
- 1 exoplanet
- Measured chemistry from 1 atmosphere
8
Q
What doppler exoplanet programs are there?
A
0.3 m/s accuracy from HARPS & HIRES (echelle grating theory & implementation)
9
Q
How many confirmed exoplanets are there today?
A
5,860: 500 earth-like by size & 70 by mass. 16 probably earth-like exoplanets (G or M Type)
10
Q
How did Kepler Graph Exoplanet Properties?
A
- PIC
11
Q
Name some probable earth-like exoplanets.
A
2015 kepler 452 b
2016 proxima centauri b
TRAPPIST-1 e, f, g
2017 Ross 128 b
TOI 715 b
Gliese 12 b
12
Q
Describe Kepler 452 b & its problems for life.
A
Distance: 1,400 ly
Size: 1.5xEarth
Mass: Unknown
Star Type: G2V (sun)
Habitable Zone: yes, star is 1.5 byrd older than sun
Surface T: 17 F
Too far to detect atmosphere
Problems: CMEs 10x those from sun observed & probably tidally locked
13
Q
Describe Proxima Centauri b & its problems for life.
A
Distance: 4.2 ly
Size: Earth
Mass: 1.3xEarth
Star Type: M
Habitable Zone: yes
Surface T: -38 F
Method: Doppler
Close enough to detect atmosphere
Problems: more stellar wind, M type stars flare a lot, probably tidally locked (liquid water on one side, ice on other)
2016 breakthrough starshot: - microchip to alpha centauri with laser propulsion & take photos of b
14
Q
Describe TRAPPIST-1 System
A
7 earth-like exoplanets with 3 in the habitable zone
Transit timing variations => densities => abundant water
Clear & obvious light curves
Habitable Zone TRAPPIST Planets: 40 lys away & M Type
- E: 0.9xEarth, -17F
- F: 1.0xEarth, -65/2000 F
- G: 1.0xEarth, -103 F
Hubble UV date => possible abundant water
Probably tidally locked
15
Q
Describe Ross 128 b & its problems for life.
A
Distance: 11 ly
Size: 1.6xEarth
Star Type: M
Surface T: 80 F
Habitable Zone
Problems: more stellar wind & little flares, probably tidally locked, no transits => hard to detect atmosphere
16
Q
Describe TOI 715 b
A
Planet Type: Super Earth
Transit (TESS)
137 ly away
3.02 Earths in mass
1.55xEarth radius
17
Q
Describe Gliese 12 b
A
Planet Type: Super Earth
Transit (TESS)
39.7 ly away
3.87 Earths in mass
0.958xEarth radius
18
Q
Describe some missions to habitable bodies.
A
Now: Perseverance searching for life below surface of Mars
2023: JUICE
2024: Europa Clipper will investigate depth, temperature & chemistry of subsurface ocean from orbit
2028: Dragonfly drone will examine conditions on Titan’s surface
2030s: Enceladus Orbilander might sample water plumes & surface
19
Q
How many habitable exomoons do we think there are among nearby exoplanets?
A
Use Earth as a model
8 planets, 3 that may be habitable (Earth, Mars, Venus)
149 moons, 3 may be habitable (Europa, Enceladus, Titan)
⅜ = 0.375 habitable moons/planet
5,800 confirmed exoplanets => 2000 habitable exomoons
20
Q
Mathematically, what is the # of habitable exomoons in the whole galaxy?
A
Furthest Kepler exoplanet = 3,000ly, radius = 0.0036 of galactic disk
2000/0.0036 = 560,000
5 million if we take into account close exoplanets
21
Q
What is the issue with habitable zones?
A
Defined by temperature for liquid water & most exoplanets not within their HZ (most too close to their star)
- PIC
22
Q
What other factors must be considered when finding exomoons?
A
Transit & doppler favor small orbits => most exoplanets close to stars
Can icy moons protect an ocean below?
Should we assume there are other exoplanets further out?
What effect will a phase-locked planet have on moon habitability?
23
Q
How are exomoons named?
A
Planet name plus roman numerals (Proxima Centauri b)
24
Q
How do we detect exomoons?
A
Transit timing variations, Sequenced occultations, doppler multiples, microlensing multiples, transit slopes
25
Describe Transit Timing Variations (TTV)
Due to planet’s wobble around planet/moon barycenter… observe brightness from transit
Hard to distinguish moons from additional planets
* PIC
26
Describe Sequenced Occultations
See many cycles to distinguish from a second planet
* PIC
27
Describe Doppler Multiples.
Moon’s component will be very small
* PIC
28
Describe Microlensing Multiples
* PIC
29
Describe Transit Slopes
Detection of exoplanetary rings
Jumps indicated by ring gaps => “shepherd moons”
* PIC
30
Describe HST data of Kepler 1625b used to confirm a sequenced transit
Kepler 1625 sun-like star 8,000ly away
Exoplanet 1625b is Neptune-like in HZ
Candidate moon Kepler 1625b I is ~mass of Neptune
Both moon & planet may be gaseous => not habitable
* PIC
31
Describe WASP Wide Angle Search for Planets
2 robotic observatories operate every night - all sky in South Africa
Detecting exoplanets by transit method (177 confirmed)
Exomoons
- 1SWASP J140747 sunlike
- 1SWASP J140747 b gas giant
2007: pattern of extended occultations of star indicated ring system around planet
- Gaps in rings suggest several exomoons all less than 0.8 Earth
* PIC
32
Describe other possible exomoons.
WASP 12b with 2 Earth mass moon
MOA (microlensing observations in astrophysics)2011-BLG-262L: rogue ice giant planet with possible moon discovered by microlensing
33
How would life on a moon change Drake’s #?
⅓ of our habitable moons have life… 567 inhabited moons
34
What methods give what measurements?
Transit: planet radius & orbit size
Doppler: orbit size & mass
Microlensing: orbit size & mass
Pulsar: orbit size & mass
Direct Imaging: radius & orbit size
35
Describe the search that inspired SETI.
1960: Frank Drake’s Project Ozma was the first search for Extraterrestrial Life
- 21cm search of 2 stars Tau Ceti & Epsilon Eridani
* PIC
1977: Signal spike received at Big Ear radio telescope at 21cm (WOW! Signal never received again)
36
Why did Project Ozma look at 21cm at stars Tau Ceti & Epsilon Eridani?
Cold Hydrogen Gas: hydrogen electron spin-flip emits wavelength of 21cm - get doppler shift to see if its coming toward or away from us
Stars are sun-like & less than 12 ly away - better chance for habitability & more radio intensity from nearby sources
37
What methods is SETI utilizing to search for life?
Looking for technosignatures in radio waves that are artificially produced
Wave Modulations: wave amplitude (am) & frequency (fm), polarization & pulse rate can be modulated to encode a message
- Amplitude Modulation (AM): amplitude modulated at different frequencies
- Frequency Modulation (FM): frequency modulation of carrier wave
Scan 800 radio frequencies at once (autocorrelation receiver) & alternate between pointing at target & nearby sky
Check for Earth-related doppler shifts to verify cosmic sources
Look for narrow-band signals => engineered source
38
Describe early SETI Programs
1979-Present (SERENDIP): listens in on other large radio telescope projects to analyze for background technosignatures
1999-2010 (SETI@HOME): published data to 90,000+ volunteers’ computers to download a program that used background power to search for technosignatures (no positive results)
39
Describe the 2019 SETI Breakthrough & Proxima Centauri
Frequency signal from Proxima Centauri b called BLC1 that persisted for 2 hours & drifted in frequency due to Earth’s doppler shift
Only present when pointed at, but faint echoes were found in off-pointings
NOT alien technology, as signal mimics common electronic instruments
40
What is Fermi’s Paradox asking?
Why haven’t we found aliens? The universe has existed for 14 billion years, suggesting civilizations might not last for cosmic timescales… last factor of Drake equation may be the limiting one
41
Name times we have sent signals to outer space.
1906: Reginald Fessenden sent radio waves from Brant Rock, MA
1972: Golden Plaques (Pioneer 10&11)
1974: Arecibo
1977: Golden Records (Voyager 1&2)
42
What are the advantages of using radio to communicate?
Focus beam to maintain intensity – Power into receiver = TPxRA/TA
* PIC
Encode message using amplitude modulation (am) & frequency modulation (fm)
Technology exists & is cheap
43
What are the disadvantages of using radio to communicate?
Time & direction limited (bigger area = weaker signal)
Requires specific technology to receive
44
How can we send signals without the limit of time and direction?
Modulate Apparent Solar Luminosity
Eject trail of organic molecules into Earth’s orbit
45
How can we modulate the apparent solar luminosity to send signals?
Opaque orbiting object (that does not look like a planet & is viewable from all direction if orbit processes) appears as a transit for 5 billion years – close orbit => frequent repeat & larger angle of view
Change intensity of transit
* PIC
Orbiter detection depends on area of visible disk (poop. r^2). Orbiter area = 10^-6 m & thickness = 10^6 m^3
Look like a rotating flat sheet (face on, edge on) with a rotation period = ¼ occultation time, sinusoidal transit light curve, more complex shape to carry coded message, tilted sheet might change orbit plane by solar wind pressure
* PIC
46
Why might ejecting a trail of organic molecules into Earth’s orbit be good for sending signals?
Limited time & angle problem
Cheap
Requires high receiver technology
* PIC
47
Describe Tabby’s Star (KIC 8462852)
Non-periodic dips in brightness & intensity
Star dimmed 22% in 2 years
Comet Swarm? (no), Dyson Swarm? (megastructure built to capture star’s energy), Probable: Protoplanet collision => uneven disk of debris
48
What is Planet 9 & how was it predicted?
Hypothetical large planet beyond the Kuiper Belt that has not been observed
Predicted by unlikely orientation of distant solar system objects
49
Describe TNO Orbits
2014: RNO orbits found to be physically clustered (some dynamic effect is required) & a massive 9th planet proposed to have caused clustering
* PIC
TNOs not only clustered in perihelions but in orbital inclinations
Cluster by random chance = 0.007%
50
What are some other explanations for clustering?
Asteroid field in distant solar system several hundred times more massive than Kuiper Belt
Interaction with another star
Coincidence or temporary alignment
51
Planet 9 Possible Parameters
Mass: 10 Earth masses
Aphelion: 1200 AU
Perihelion: 200 AU
Eccentricity: 0.6
Inclination: 30 degrees
Orbital Period: 15,000 years
52
Planet 9 Possible Origin
Far reaches of solar system are not dense => unlikely it could form there
How did it get there? Another stellar system? Formed closer to sun & migrated?
53
Where is Planet 9 now?
If near the perihelion, we could identify it from imagery, but it is likely near aphelion & very very dim
* PIC
Cassini craft measured Earth/Saturn distance for decades (so we could tell if Saturn was being pulled by something beyond Neptune) & recorded slight perturbations, placing it in the middle of the band of the Milky Way
Might still be cooling from formation & be visible in infrared
* PIC
54
What is ‘Oumuamua? First messenger from afar
First detected extra-solar object to orbit the sun
Cigar or disk shaped rocky object that probably drifted through interstellar space for hundreds of millions of years (not spherical)
Brightness changes as it reflects sunlight
Hyperbolic orbit
Discovered by Pan-STARRS1 high resolution camera that tracks near Earth Objects
55
Describe ‘Oumuamua’s trajectory.
Came from constellation Lyra, star Vega (25 ly away) - would take so long to reach us that Vega was in a different position & outgassing acceleration makes calculating origin more difficult.
Going in the direction of Pegasus, travels 1 ly every 11,000 years
* PIC
56
‘Oumuamua Parameters & Acceleration
400-800m long
10x longer than it is thick from brightness changes
No dust = bright red color
Very dense & spectrum reveals possible subsurface ice
17 m/s acceleration likely due to outgassing pressure from solar heat & could indicate artificial origin
57
‘Oumuamua Origin Theory
Likely ejected gravitationally by a large planet during a stellar system formation
Larget planet disrupted another planet in formation & ejected planetesimals
58
Describe Comet 2I/Borisov
Coma of sublimated gases - Carbon monoxide in high concentration
* PIC
59
What did we expect at the edge of the solar system?
Bow shocks that are intense around young stars
Stellar winds could collide with interstellar gas to produce a shock front
* PIC
60
Describe Bow Shocks & what they might look like.
Planets have bow shocks caused by high velocity solar wind
Saturn, Earth, Mars, & Venus (stationary bow shock that may have been caused by mountains)
* PIC
Sun’s Bow Shock
* PIC
61
How have we observed the solar boundary?
Pioneer 10
- Plasma in Jupiter’s magnetic field
- Flying towards tail of heliosphere
Pioneer 11
- Confirmed Saturn bow shock
- Crossed Jupiter’s bow shock => Jovian magnetosphere changes shape by solar wind impact
- Flying towards solar bow shock
Voyager I & II
- I is above ecliptic plane - Saturn
- II is below ecliptic plane - Jovians
* PIC
62
What are the defining parts of the heliopause?
Heliosphere: whole bubble of solar influence
Termination Shock: slowdown & compression of solar wind
Heliopause: boundary between solar wind & interstellar wind
Bow Shock: shock wave as heliosphere plows into interstellar space
* PIC
63
What changes would you expect to find at the heliosphere boundary?
Magnetometer: studied magnetic field of heliosphere
- Detection of weak steady interstellar field, B
- Magnetic foam in heliosheath
Cosmic Ray Subsystem: measurement of energetic particles in magnetospheres of outer planets
- Detects particles per second using high energy (for interstellar particles) & low energy telescope (for solar particles)
-Shift into interstellar space shows drop in solar particle detection
- Heliopause crossing happens at 120 AU when velocity of plasma from Sun drops to zero
64
What is IBEX?
2008 Earth orbiter with electrically neutral interstellar particle detectors (2 for high & low energies)
Tracked sun’s path through local fluff of interstellar gas
65
What is terraforming?
Altering a hostile environment to make it suitable for terrestrial life by changing surface temperature, atmospheric pressure & composition, magnetic field protective envelope
66
Why terraform?
Backup Planet: global warming, pandemic, nuclear war, overpopulation
Earth resources limited: more rare Earth elements need for industry, helium running out, not enough potable water
More knowledge to save Earth
67
What conditions do we need to overcome to terraform Mars & why?
Temperature (-176C to 30C), need to warm the surface
- No planet growth & little liquid water
Atmospheric Pressure (0.5% Earth’s), need to increase pressure
Atmospheric Composition (0.5% Earth’s oxygen), need to convert CO2 to oxygen & supply nitrogen
Weak Magnetic Field: little shielding from solar wind & new atmosphere will disappear again, so we need to build a field or shield
68
How do we terraform Mars?
Build dirty factories to spew smoke & CO2 to produce greenhouse effect
Seed the atmosphere with lichen to convert CO2 to O2
Sublimate the polar caps with orbiting mirrors reflecting sunlight to increase greenhouse effect
Redirect asteroids or comets to seed Mars with ammonia that dissociates into nitrogen gas
Nuke mars to sublimate caps & surface ice to increase greenhouse effect
Build shield to block solar wind
69
Pros & Cons of building dirty factories to spew smoke & CO2 to produce greenhouse effect (MARS)
Pros:
- Raises temp & pressure slowly
- Might increase oxygen gas
Cons:
- No effect on magnetic field => atmosphere lost
- How do we supply fuel?
- Tech not available
70
Pros & Cons of seeding the atmosphere with lichen to convert CO2 to O2 (MARS)
Pros:
- Increase oxygen
Cons:
- No effect on magnetic field => atmosphere lost
- Lichen may not survive
- Decrease greenhouse effect => colder
- No direct effect on pressure
- Tech not available
71
Pros & Cons of sublimating the polar caps with orbiting mirrors reflecting sunlight to increase greenhouse effect (MARS)
Pros:
- Raises temperature, pressure, & oxygen
Cons:
- No effect on magnetic field
- Maybe not enough in caps
- Tech not available
72
Pros & Cons of redirecting asteroids or comets to seed Mars with ammonia that dissociates into nitrogen gas (MARS)
Pros:
- Raises temperature, pressure, nitrogen
Cons:
- No effect on magnetic field
- Tech not available
73
Pros & Cons of nuking mars to sublimate caps & surface ice to increase greenhouse effect (MARS)
Pros:
- Raise temperature & pressure
- Might produce oxygen
Cons:
- No effect on magnetic field
- Unpredictable
- Nuclear fallout
- Tech not available
74
Pros & Cons of building shield to block solar wind (MARS)
Pros:
- Don't need to build magnetic field
Cons:
- Lower temperature & pressure
- No predictable effect on composition
- Tech not available
75
What conditions do we need to overcome to terraform Venus & why?
Temperature (480C), need to cool surface temperature
Pressure (90atm), need to reduce pressure for reduced temperature for liquid water
Atmospheric Composition (96% CO2), convert CO2 to O2 & N
No magnetic field to protect from solar wind, need to build a field or block it
76
How do we terraform Venus?
Seed atmosphere with algae to convert CO2 to O2
Seed atmosphere with hydrogen to get water
Block sunlight & solar wind with a shade at sun/Venus L1
Floating habitat in atmosphere where pressure & temperature are similar to Earth’s
77
Pros & Cons of seeding atmosphere with algae to convert CO2 to O2 (VENUS)
Pros:
- Raise oxygen & decrease greenhouse effect/pressure
Cons:
- No effect on magnetic field
- Organisms will not survive sulfuric acid layers
- Tech not available
78
Pros & Cons of seeding atmosphere with hydrogen to get water (VENUS)
Pros:
- Raise oxygen & decrease greenhouse & pressure
Cons:
- No effect on magnetic field
- Elevate catalyst like iron
- How do we transport hydrogen
- Tech not available
79
Pros & Cons of blocking sunlight & solar wind with a shade at sun/Venus L1 (VENUS)
Pros:
- CO2 liquifies & falls
- Decrease greenhouse & lowers pressure
Cons:
- No effect on magnetic field
- Liquid CO2 needs to be sequestered
- Tech not available
80
Pros & Cons of floating habitat in atmosphere where pressure & temperature are similar to Earth’s (VENUS)
Pros:
- Quick
- Blocks sunlight to reduce temperature slowly
- Powered by solar panels
Cons:
- No effect on magnetic field
- Hard to transport N & O2
81
How do we create a floating habitat on Venus?
From buoyancy at the surface, you would weigh 5.9% of your weight on Earth
At a high altitude, Venus air density is less & a helium balloon could float, but it might be in the sulfuric layer
Hydrogen balloon would float much higher, lift 1.46 million kg if 10^6 cubic meters, but there is no oxygen to ignite it.
* PIC
82
Why is terraforming the moon not an option?
Low escape velocity, no atmosphere, consider habitable pods
83
What space agreements are there? Is there a law permitting or forbidding space mining?
No, there is no law permitting or forbidding space mining.
Outer Space Treaty 1967: exploration & use of space is free for all states but must benefit mankind, no country can claim sovereignty, states are responsible for damage
Rescue Agreement 1968: rescue and return of astronauts
Liability Convention 1972: liable for damage
Registration Convention 1976: registration of objects in space
Moon Agreement 1994: bans military use of celestial bodies
84
Why mine the moon?
Learn about the local solar system
Derive necessary & rare resources to bring to Earth (oxygen, silicon, iron, water ice, helium 3, rare Earth metals)
84
Describe some private space companies and their goals.
Firefly Blue Ghost: first successful commercial lunar soft landing
SpaceX: launch NASA’s lunar Artemis II mission
Blue Origin: soft land Artemis III astronauts on the moon
Offworld: AI company building industrial robots to mine
85
Name asteroid types & what we get from them.
C-Type (Carbonaceous): outer region of asteroid belt, clay/silicate rocks containing 22% water
S-Type (Siliceous): inner asteroid belt made of stony materials & nickel-iron
M-Type (Metallic): middle region of asteroid belt made of nickel & iron
86
What are the most valuable metals on asteroids?
Platinum Group Metals (Ru, Rh, Pd) are high value
Industrial Materials (Fe, CO, Ni)
Volatiles (H, C, N, O) & water molecules
87
How do we select asteroids to mine?
Proximity to Earth (earth-sized with low eccentricity)
Size: <200m in diameter difficult to stick a landing due to low gravity
Composition: M-Type
88
Describe asteroid exploration missions.
OSIRIS-Rex: type M asteroid Bennu
- 500m in diameter, 1.2 period, soft surface with 1/2 lb sample return
Dart: move binary asteroid from orbit, change is measured by period shift
Lucy: research mission to learn about original protosolar cloud
Psyche: determine in M-Type 16 Psyche is core of unformed planet & is valued at 10 quintillion
89
Name some mining techniques.
Land & work inside or with tethers/anchors
Tow it back to moon
Bring raw ore or reduced metals back to Earth/moon
Manufacture in place at the asteroid
90
State the 3 factors you consider most important in determining if an exoplanet is earth-like, and 3 additional facts that you consider less important.
Habitable Zone Factors: Distance to star where T is right for liquid water
Orbit size
Atmosphere
Tidal Lock
Radius
Mass
91
List the steps involved in determining the mass of an exoplanet by the Doppler method, using words and/or equations. There will probably be between 3 & 6 steps. Assume we see the orbit edge on.
Star’s doppler yields orbital period & velocity due to companion
Star’s orbit size calculated (2pia/p = v) & spectral type yields mass
Knowing period & m+M, kepler’s 3rd gives orbit size
m/M is calculates to get planet mass
Yields only orbit size & planet mass
* PIC
92
Draw a light curve of a star that indicates an orbiting exoplanet with an orbiting moon, including a time interval for 3 planetary orbits.
* PIC HELP
93
Draw 1 or 2 diagrams of a star, an exoplanet orbiting it, and an exomoon orbiting the exoplanet, that illustrate how the exoplanet transit can be advanced or delayed
* PIC HELP
94
Describe how the 21 cm spectral line is emitted and why we often search in that wavelength for extraterrestrial life.
Hydrogen electron spin-flip emits a wavelength of 21 cm
Assume intelligent civilizations know it because it is so abundant & natural
* PIC
95
Describe 1 reason why signal BLC1 suggested intelligent origin, and 2 reasons why it eventually did not.
Breakthrough watched Proxima Centauri & its planet Proxima b. The frequency persisted for 2 hours & was originally not in the offpointings. Now echoes were found in the offpointings & the signal mimics common electronic instruments.
96
If there is a planet 9, why would it most likely not be detectable in existing imagery, and how have we eliminated sections of its presumed orbit for its present location?
Planet 9 would likely be closer to its aphelion 1200 AU away & is very dim. Cassini craft measured Earth/Saturn distance for decades (so we could tell if Saturn was being pulled by something beyond Neptune) & recorded slight perturbations, placing it in the middle of the band of the Milky Way
97
Name the big 5 mass extinction events.
Caused by temperature changes
End Ordovician (444 Mya)
Late Devonian (360 Mya)
End Permian (250 Mya)
End Triassic (200 Mya)
End Cretaceous (65 Mya)
Believe we're in the 6th, human population increases with species extinctions
98
What was the K-T Extinction?
Extinction of the dinosaurs (Cretaceous-Tertiary)
1980: Comet Impact Theory of Luis & Walter Alvarez iridium layer discovery at correct geologic time
1994: Chixculub Crater, no sulfur & did not cause ice age
99
Name ways to die by an impact crater.
Starve: impacts raise molten rock into air to block sunlight & cause impact winter, sulfur combines into sulfates in atmosphere making it opaque, food chain suffers from cold temperature
Crush: atmosphere shock wave
Fry: Wildfires
Drown: Water impact produces tsunamis
100
Name possible causes of ice ages.
Continental drift, blocks ocean flows
Concentrations of atmospheric CO2 or dust
Volcanic Eruptions
Ice reflects sun => runaway cycle of decreasing T
Cycles in Earth’s orbital configuration = Milankovic Cycles
101
Describe Molankovic Cycles
Changes in eccentricity (shape)
- Eccentricity is bigger => colder at aphelion, warmer at perihelion
- 100,000 year cycles
Changes in tilt
- bigger/smaller tilt changes contrast of summer & winter => tilted less = more consistent temperature year round
- 41,000 year cycles
Changes in axial precession (wobble)
- Direction polar axis aims in space
- 26,000 year cycles
102
Describe correlations in Molankovic cycles
Vostock 1998: correlation between Milankovic & Antarctic Temperature
EPICA Ice Core: correlation between ice volume, CO2 level, dust level, temperature anomoly
103
Using transit method to detect exoplanets using spectroscopy.
Transit in red light dims the least because blue light scatters more
Intensity of scattered light, I prop. D^6 is how rapidly stars dim due to atmosphere
Smaller particles scatter blue light more (Rayleigh)
Larger particles scatter longer wavelengths
Very large particles scatter all wavelengths
104
Describe sampling transit time variations to detect exoplanets.
Low molecular weight atmospheres will be tall & pass in front of a star over a long sampling time
High molecular weight atmospheres will be low (compressed towards surface) & pass in front of star over a shorter sampling time
No atmosphere, transparent, or cloudy will block star’s light & have no sampling time
105
Describe K2-18b
Found by Kepler highly accurate pointing maintained by 3 reaction wheels steered by slowing/speeding rpm so angular momentum changes - they failed. Use solar photon pressure stabilize axis to point.
2017: b orbits M type star 124 ly away
- Probably tidally locked, gas giant, 8.6 Em, 2.6 Er, 33 day period, & possibly liquid surface
April 2025: spectral evidence of dimethyl fluoride & dimethyl difluoride produced on Earth by micro-organisms
106
How do we pulverize asteroids
Bury explosives into it:
- Terminal Defense – Fragments small enough to burn up, but results are uncertain. Could be set up in advance.
Nuke it: Illegal, diplomatic problems, unpredictable results
107
How do we divert asteroids?
Problems:
- May endanger another area
- International Diplomacy
- Advanced setup
- Tech not available
Mine It: NASA MADMEN: robot drilling rigs mine asteroid & pieces ejected in the same direction to divert orbit (propulsion)… ionize debris, mechanical catapult, cannons
Paint It: All white so photon pressure diverts orbit very slowly (5 tons of paint & 20 years for Apophis)
Sail It Away: Attach a huge sail (1km^2 for 5 years) so solar photon pressure diverts orbit slowly. Asteroid rotation problems.
Push It: Too much fuel & either stop the rotation or plant rockets around it
Pull It: Park craft near an asteroid & gravitation will divert orbit & crash. Ion drive retro-rockets can maintain separation, and push the asteroid back by aiming at an angle.
Coax It: Orbit gravity tractor using Ion drive to keep ahead of NEO. Asteroid rotation or shape is not a problem & fuel usage is more efficient than strapping rockets.
Cook It: Mirror bees reflect sunlight onto an asteroid & vaporize a small spot. Momentum of released vapors diverts orbit, but asteroid rotation & maintaining bees are problems.
Threaten to Nuke: H bomb nearby & photon pressure diverts orbit, but dangerous & unpredictable.
Nuke Near It: Divert by releasing asteroid vapors quicker. Treaties prohibit, dangerous of partial fragmentation.
Throw Rocks at It: DAWN Spacecraft diverted Tempel 1 orbit 10cm with copper impactor.
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Describe the DART mission.
Study effect of impact on asteroid dimorphous (100 MT impact energy)
Binary asteroid targeted so effect on orbit can be measured through its period of revolution (smaller, faster, shorter period orbit)
Rail cars of material blasted from surface & transfer of momentum was 3.6x greater than if no material was blasted
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