Terrestrial Planets Flashcards

Terms Definitions
mars day
24hrs 40minutes
Venus is dominated by what?
plate tectonics
unifying geological theory which explains almost all geological processes by the interaction of lithospheric plates driven by convection currents in the mantle which are in turn driven by the heat flow from the Earth's still hot interior; in effect the Earth's surface in recycled over geologic time periods, especially the ocean crust which is generally less than 200 million years old
Present-day atmospheres
Very diverse, despite primordial atmospheres
venus' atmosphere
the average surface temperature was too hot for water to condense and the water vapor and CO2 caused a "runaway" greenhouse effect with surface temperatures soaring higher than even the present 740K average temperature; the water vapor was disassociated ("broken apart") into oxygen which chemically combined with surface rocks and hydrogen which was lost by the process of thermal escape leaving a massive, mostly CO2 atmosphere with a surface pressure of 90 bar (1 bar = surface presure on Earth) and an intense greenhouse effect giving Venus the hottest surface temperature in the solar system
evidence of water by drainage patters similar to those made by streams
Surface Features: Venus
basaltic volcanism and tectonic activity shape venus's surface. based on the low density of impact craters, these forces must have been very active during the recent geologic past.
Has the right temperature for liquid water, its gravity is strong enough to retain its atmosphere
**atmospheric circulation difference due to rotation speed (Earth vs. Venus)
Earth- rapid rotation= circulation patterns are broken into smaller cyclonic disturbances Venus- slow rotation=circulation isnt broken up but instead is organized as a planetwide wind pattern
Describe the general interior structure of a terrestrial planet. (Use Earth's structure as the example.) Talk about chemical layering and physical layering. How does the surface to volume ratio affect the interior structure?
1. general structure:
a. chemical layering
i. dense nickle-iron core
ii. mantle of dense rock
iii. thin crust of low density rock
b. physical layering, details depend on planet
i. rigid upper mantle and crust: lithosphere
ii. "plastic" layer of mantle beneath lithosphere: asthenosphere
iii. molten outer core (Earth only?)
c. surface/volume ratio higher for small worlds (goes as 1/radius)-> small worlds have lower heat capacities and lose heat at a faster rate, larger worlds retain the heat of accretion and radio-active decay longer
Surface Features : Mercury
mercury has cratered highlands like the ones on the moon, mercury is very dense, it has scarps (deep slopes)
shield volcano
formed by highly fluid lava that flows easily and creates low-profile volcanoes
Describe the specific characteristics of the surface of Mars and compare them with Earth's surface features. What can we say about plate tectonics on Mars?
ne hemisphere heavily cratered with maria similar the Moon, the other hemisphere boasts the largest shield volcano and rift valley in the entire solar system; indicates arrested development of plate tectonics, planet cooled quickly which resulted in a thick lithosphere which could not be broken up into plates by the residual heat
the martian atmosphere
the atmosphere of mars is very thin. extensive dust storms occur and cause color changes observed from Earth. Hurricane force winds up to 270 km/hr can go on for weeks.
Which gas is most abundant in the atmospheres of Venus and Mars?
Carbon dioxide (CO2)
Interiors of the small terrestrial planets
Cooled rapidly and have solidifiedmercury & mars have thick, rigid crusts; no plate tectonicsmercury has signs of ancient volcanic vents
Where did Venus' water go?
It was broken up by ultraviolet radiation from the sun.
Describe the atmospheric layers in the Earth's atmosphere
a. Troposphere: greenhouse gases trap IR radiation; heated from below by surface warmth, temperatures decrease with height, convection causes "weather"
b. Stratosphere: heated by UV light (Earth's ozone layer) temperature constant or rise with height eliminating convection (no convection); no UV absorbing molecules = no stratosphere
c. Thermosphere and Ionosphere: X rays heat and ionize gases causing increasing temperature with height
d. Exosphere: heated by solar UV and X rays, high speeds and long free paths (due to very low density) make this the region of greatest thermal escape; Moon, Mercury with no real atmospheres (some atoms due to radiation bombardment of surface and capture of solar wind particles) have only exospheres
venus' lack of protection from solar winds is caused by
the lack of a magnetic field
What does mercurys surface look like?
looks somewhat similar to the far side of Earth's moon.
how does water vapor disapear on venus?
it was broken up by ultraviolet radiation until it disapeared
How are seismic waves used to determine detailed structure of a planet? What planets have we studied using seismic waves?
only used on Earth and Moon, can provide detailed knowledge of internal structure
What was the 1st atmosphere made up of and where did this gas come from?
1st marginal atmospheres may have been H2 from solar nebula, but the 1st robust atmospheres were derived from volcanic out-gassing and icy planetesimal impacts (sometimes called the secondary atmospheres), these so called secondary atmospheres are thought to have had the same composition for all terrestrial planets: ~½ water vapor, ~½ carbon dioxide, lesser amounts of nitrogen and other volatiles; modification of this original atmospheric composition through several loss processes has produced the present atmospheres of the terrestrial planet
What evidence do we have that the Martian atmosphere was denser in the past than it is today?
The abundance of Argon by mass is 1.6% + we have observed dry streambeds and outflow channels.
valles marineris
radar pulses
Venus topography mapped using
rock content on venus is
Same as the moon in size
Mars' atmosphere
the average surface temperature was warm enough with the greenhouse effect caused by the water vapor and CO2 for water to condense (perhaps into ocean sized regions?); as the CO2 was absorbed (dissolved) into the oceans where it was precipitated out of solution by chemical (and life?) processes and was being locked into carbonate rock the greenhouse effect was reduced, also as Mars cooled internally its nickel-iron core solidified and the planet lost its protective magnetosphere - allowing the solar wind to directly interact with the upper atmosphere slowly stripping the gas away by "bombardment", both these processes continued to reduce the greenhouse effect until the average temperature dropped below the freezing point of water; the atmospheric pressure also dropped to the point that liquid water could not exist and the water vapor left in the atmosphere was disassociated into oxygen which chemically combined with surface rocks (hence the "red" surface rocks of Mars) and hydrogen which was lost by the process of thermal escape leaving a thin, mostly CO2 atmosphere, a portion of which seasonally "freezes out" to form the "dry ice" polar caps over top of the permanent water ice polar caps. Evidence from the Mars Exploration Rovers have confirmed that Mars once had bodies of liquid water on its surface.
Which one has a "runaway greenhouse effect"?
Surface temperature: Venus
atmosphere is 97% carbon dioxide.
composite volcanoes
volcanoes form above subduction zones where the descending crust melts and the magma rises to the surface. This forms subduction zones. (steep slopes) often burst
Moon's atmosphere
the warm surface temperature and very low surface gravity combined with (perhaps) its giant impact origin which denuded the bulk material of the Moon of all of its volatiles causing it to lose any atmosphere it had (or acquired later by bombardment of icy planetesimals) due to thermal escape, leaving virtually no atmosphere
named for the goddess of love and beauty
mean density
average mass density of the planet = (mass of planet)/(volume of planet); combined with assumption that all differentiated terrestrial planets have the same general structure, the relative sizes of the core, mantle, and crust can be estimated using mean density
size, density, mass, location
Venus is the Earth twin because
axis degree of mars
23.5 degrees (so it has seasons)
specific characteristics of the interior structure of Earth.
Earth: most detailed knowledge from analysis of seismic waves, outer core molten (S wave shadow zones, strong planetary magnetic field), residual heat flows from core to surface by convection currents in outer core, mantle and asthenosphere (plastic part of mantle) driving the interaction of many rigid lithospheric plates at the surface
Which is something about Venus and Earth that is different (3)
surface temperature, atmospheric pressure, atmospheric composition
two types of seismic waves
i. P waves = primary-fastest wave speed, longitudinal waves, propagates through solid or fluid
ii. S waves = secondary-slower wave speed, transverse waves, does not propagate through fluid
slippage of material along huge faults in the crustal layer
Canyons on mars formed by?
Interiors of large terrestrial planets
Cool more slowly and are still partially liquidvenus & Earth are kept warm by energy
Where did Mars' water come from?
Volcanic degassing is known to release water vapor.
two other methods or measurements that can be used to determine more details about a planet's interior structure.
c. spacecraft flybys: some details of the internal structure may be inferred by analysis of trajectory perturbations
d. planetary magnetic field strength: planetary magnetic fields generated by rapid rotation, combined with a molten, electrically conducting core - some conditions within core may be inferred by presence/absence, strength of planetary magnetic field
Why might Venus have the slow retrograde rotation?
1)A large off-center impact may have set Venus spinning backwards 2)the long-term effect of solar tides on its dense atmosphere may be responsible.
The ability of a planet to retain an atmosphere depends on:
Its mass and temperature-massive planets have a high escape speed; cold planets have slow-moving atmospheric molecules
How do we know what the surface of Venus looks like?
Radar mapping at radio wavelengths allows us to determine surface elevations.
how could the abundance of deuterium develop on venus?
b/c venus has no ozone layer to absorb the ultraviolet radiation in sunlight
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