Untested Materials (Lecture 7, 17-23) Flashcards
The six successful Apollo missions
Apollo 11, 12, 14-17
Apollo 11 geological goal and results
Goal: Sample relatively old mare surface
Results: ~3.7 Ga basalts high in Fe, Ti; Water not important; Maria is very old; Maria is volcanic
Apollo 12 geological goal and results
Goal: Sample relatively young mare; possible ray from Copernicus
Results: ~3.15 to 3.35 Ga; “young” maria are very old; Copernicus may have formed approximately 0.9 Ga ago; Granite exists on the Moon
Apollo 14 geological goal and results
Goal: Sample Imbrium ejecta, possibly deep material
Results: a variety of breccia, ~3.9 to 4.9 Ga; no deep material; Region is ejecta blanket of Imbrium basin; Imbrium basin formed approximately 3.9 to 4.0 Ga ago; Trace-element-enriched rocks very abundant
Apollo 15 geological goal and results
Goal: Sample mountainous rings of Imbrium basin, Hadley Rille
Results: ~3.2 Ga mare basalts, ~3.9-4.1 Ga breccias; Imbrium mare is not produced by impact; Rille related to collapsed lava tubes; highlands complex in composition
Apollo 16 geological goal and results
Goal: Sample breccias ~3.8-4.2 Ga
Results: impact breccias ~3.8-4.2 Ga; Most flat highland areas formed by pooled impact ejecta, probably related to major multi-ringed basins; highlands are anorthositic
Apollo 17 geological goal and results
Goal: sample massifs from older basins, flat valley plains between mountains and dark mantling
Results: a variety of breccias ~4.0 Ga, basalts ~3.7 Ga, volcanic glass ~3.5 Ga; Very young volcanism not evident; a variety of breccias may represent older events
Significance of the Soviet Luna Missions
Sampled the far side of the moon and was unmanned.
Advantages and disadvantages of human space exploration
Advantages: Rovers can only do so much. Humans have unique, on-the-fly decision-making abilities
Disadvantages: Human exploration is very difficult. For each 3-man mission, there were hundreds, if not thousands of people on Earth). Also the risk of human death
New Horizon Mission objectives
- Map the surface composition of Pluto and Charon
- Characterize the geology and morphology of Pluto and Charon
- Characterize the neutral atmosphere of Pluto and its escape rate
IAU definition of a planet
A celestial body that is in orbit around the Sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium shape, has cleared the neighborhood, around its orbit
IAU definition of a dwarf planet
A celestial body that is in orbit around the Sun has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium shape, has not cleared the neighborhood around its orbit, and is not a satellite
Alternative planet definition
any body in the solar system that is more massive than the total mass of all of the other bodies in a similar orbit
Geophysical definition of a planet
a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape, regardless of its orbital parameters
Exoplanet
A planet outside of the Solar System
Why is it difficult to find exoplanets?
- Planets don’t produce their own light
- They are very far away
- They are lost in the blinding glare of their star
How to find exoplanets?
- Radial velocity (swaying of the star due to planets)
- Astrometric measurement
- Transit (planet crosses in front of the star)
- Direct imaging
- Gravitational lensing
Three missions that have contributed to finding exoplanets
The MOST mission (Canada), the Kepler mission, and the Tess mission (USA)
Star’s habitable zone
Comparing the surface temperature of a star with energy received by planets around it. The habitable zone is the distance from the star that water could exist on a planet and water is vital for life
Planetary matter
- Chemical composition (refractory vs. volatile)
- Size/mas (how much accreted)
Planetary energy
- Amount (how much originally, and since)
- Type (accretion, radioactivity, core formation (differentiation), tidal, solar, impact)
How is Earth just right for life?
- Plate tectonics (recycles crust, regulates carbon cycle)
- silicates + eater (the right starting materials
- Differentiation (atmosphere, from degassing)
- Gravity to hold gases (and hold atmosphere)
- Distance from the Sun (hydrologic cycle, habitable zone)
Where else would you look for life in the Solar System?
- Europa (subsurface ocean/tidal heating/organics)
- Titan (subsurface ocean/tidal heating/organics)
- Mars past (water/habitable zone/organics?)
- Venus past (water/habitable zone/organics?)
- Io? (tidal heating, but lacks water)
- Enceladus (subsurface ocean/tidal heating/organics)
- Ganymede (subsurface ocean/tidal heating/organics)
Why are sample returns so important?
- Rover instruments are limited in the amount of information they can provide
- Analyses on Earth are much more advanced
- We get to pick where the samples are collected
Impactite
Broad term for rocks affected by a hypervelocity impact event from within the crater to beyond the ejecta blanket
Macroscopic evidence of terrestrial impacts
crater morphology, shatter cones
Microscopic evidence of terrestrial impacts
planetary deformation features (PDFs), planar fractures (PFs), diaplectic glass in quartz or feldspars, high-pressure polymorphs (quartz, olivine, graphite)
Reasons why impact craters are not as distinct or easy to identify on Earth compared to other solid surfaces in the Solar System
- Atmosphere (smaller meteoroids breakup/do not reach the ground)
- Oceans (cover ~70% of the surface -> no craters)
- Plate tectonics (old rocks are limited
- Burial (sediment infill and cover craters over time)
