Ch 9+10 Flashcards
Why is it hard to tell depth on the moon?
You expect to see shades of shadows on a gray scale, but in reality it’s only black and light.
Moon Composition
Highlands (83%), Mare/Maria – flat plains of basaltic lava (17%)
How do craters form?
Crater hits, “comes out”, and particles fall back into hole that was made
Cold Traps on Moon
Where the sun’s rays never shine (poles of moon) ice in crater is unmelted
Highlands on Moon
- Made of relatively low-density rock that solidified on the cooling Moon
- Extremely heavily cratered, bearing scars of billions of years of impacts
Maria
-dark colored basalt (volcanic lava) laid down in volcanic eruptions years ago
Moon’s Surface
- fine grained soil of tiny, shattered rock fragments
- upper layers are porous with loosely packed dust
Impact Craters
Regardless of size or angle of impact, they are roughly round & circular
Formation of Impact Craters
(1) Impact occurs
(2) Projectile vaporizes and a shock wave spreads through the lunar rock
(3) Ejecta are thrown out of the crater
(4) Most of the ejected materials fall back to fill the crater, forming an ejecta blanket
Fission Theory
Moon was once part of Earth, but somehow separated from it early in history
Sister Theory
The Moon formed together but independent of Earth
Capture Theory
The Moon formed elsewhere in the solar system and was captured by Earth (least likely theory)
Avg Distance of Mars from the Sun
227 million kilometers (1.52 AU)
Avg Distance of Venus from the Sun
108 million kilometers (0.72 AU)
Appearance of Venus
- Appears very bright, featureless white ball
- Goes through phases like Moon
- Planet’s surface not visible b/c of dense clouds that reflect 70% of sunlight
Appearance of Mars
- Distinctly red due to iron oxides in soil
- Bright polar ice caps
- Dusky surface markings that sometimes change in outline and intensity
Venu’s Surface
Lowland lava plains (75%)
Impact Craters on Venus
- Gertrude Stein: Triple impact crater
- Mrs. Piggy Corona
- Mead: Largest crater
Atmosphere of Venus
- CO2 (96%) then N2 – overall very dry atmosphere, absence of water
- Huge troposphere
- Almost 800 K on surface
Polar Ice Caps on Mars
Mars has 2 year orbit so polar ice caps from 6 month long winter in each hemisphere
Percival Lowell
A french astronomer that described what he saw on Mars as channels, but were mistranslated to canals (man-made)
Mariner 9
1971, first spacecraft to orbit another planet, mapping entire surface of mars
Twin Viking Spacecrafts
1970s, two orbiters surveyed planet and relayed communications for two landers on the surface
Mars Global Surveyor (MGS)
- 1997, took high-resolution photos of entire surface for more than one martian year
- Discovered gullies apparently cut by surface water
Odyssey
Discovered large amount of subsurface hydrogen
Pheonix
-2008, measured water ice in the soil
Curiosity
2011, goals include investigations of climate, geology, assessment of habitability of past and present Mars
Atmosphere of Mars
- Avg surface pressure of only 0.007 bar
- CO2 (95%), N2 (3%), Argon (2%)
- Winds can reach high speeds but exert much less force than wind on Earth b/c thin atmosphere
Runaway Refrigerator Effect
Mars is smaller planet, lower gravity, more and more atmosphere escaped into atmosphere – Mars became cold most of water froze out – further reduced ability to retain heat
