astro quiz 3 ch 19-

Lecture 19-

planetary evolution

What three factors affect the evolution of surfaces of terrestrial planet

Impact cratering, volcanism, tectonics

What planets are shaped mostly by impacts and early volcanism

Mercury and Mars

What planets are primarily shaped by tectonics?

Venus and Earth

Planet cooling depends on what two factors

Size and temperature

(Hot/cold) planets cool faster than (hot/cool) planets

Hot, cool

(Large/small) planets cool slower than (large,small)

Large,small

what generates the earths magnetic field?

Rotating metal core and convection

The magnetic field helps the atmosphere _

Block charged particles from solar wind

Mercury’s atmosphere

Doesn’t exist

Venus’s atmosphere

Hot CO2

Earth’s atmosphere is

Warm wet N2 and O2

Mars’ atmosphere

Dry, thin, CO2

Volcanism and techtonics

Driven by internal structure of planet, needs hot interior

Shapes of small terrestrial planets are shaped by

Impacts and early volcanism

Impact cratering is most important during the _ of the solar system

first Gyr

Crustal shaping primary vs secondary

Primary: shaped by impacts

Secondary: volcanism

Surfaces of large terrestrial planets are (old/young), with active _ from plate tectonics

Young, tertiary crust

Earth-

Plate techtonics and lateral recycling

Venus-

One plate crust and vertical recycling

Vertical recycling types

Pancake domes, coronae

Pancake domes

magma upwelling pushing up the crust

Coronae

Magma down-welling collapsing the crust

First stage of planet evolution: _ (heat of formation)

differentiation; Dense molten metals sink into core, lighter silicate rocks float to crust

Second stage of planet evolution

Volcanism; mantle molten from residual internal heat + heating by radioactive decay and heavy impacts, magma rises to surface as volcanoes

Primary factor in whether a terrestrial planets cool slower has a hot interior and is geologically active on the surface?

radius

Cooling time of a terrestrial planet scales with _ of planet

Size/radius

Energy is lost via (heating/cooling) by _ from the surface

Cooling, radiation

Cooling time

Ratio of total energy to the loss rate

Hotter bodies lose energy (faster/slower) than colder bodies

Faster

Larger bodies lose energy (faster/slower) than small bodies

Slower

Currently, the small terrestrial planets have _ interiors than the large terrestrial planets

Cooler

Interiors of small terrestrial planets cooled rapidly and have mostly _

Solidified (ends techtonics)

Solid mantle means

Tectonic activity is ended

All small terrestrial planets have (thick/thin),(hot/cool),(smooth/rigid) crusts

Thick, cool, rigid

Large terrestrial planets cool more slowly and are still (hot/cool) from radioactive elements

Hot

How do large terrestrial planets stay hotter for longer?

Radioactive decay of elements

Convection motions in molten mangled drive _ and gives earth and venus active _ crusts

Tectonics, tertiary

_ of a planet is necessary for an atmosphere and habitability

Internal heat

Small planets (have/don’t have) internal heat so they (are/aren’t) geologically active

Don’t have, aren’t

No geological activity means

Planet unable to replenish atmosphere (volcanoes), no heat flow to center, no convection, no plate tectonics, no CO2 cycle, no magnetic field

Internal heat drives _

Convection

Convection drives _ _

Plate techtonics

CO2 cycle that regulates global climate requires

plate tectonics

Convection+rotation generate a planetary

Magnetic field

Magnetic fields protect atmospheres from damage by

Solar wind

Solar wind is made of

Charged particles (which cannot enter magnetic field lines)

What was the effect of solar wind of mars’ atmosphere

Accelerated the loss of it

Whats a phenomenon on earth thats caused by solar wind particals

Aurora borealis

Magnetic field protects earth from

Chipping away

Key to life (regulate climate, block radiation, liquid water)

Atmosphere

Mars has a thin atmosphere today as the result of (3)

Escape of gas particles due to low gravity, lack of magnetic field, lack of volcanoes to replenish the atmosphere

The atmospheres of the terrestrial planets all started out roughly _

The same

During formation, the terrestrial planets were _ from asteroid impacts and too (hot/cold) to hold atmospheres

Molten, hot

primary atmosphere formation

Formation gas at protoplanetary disk, H and He escaped quickly

Secondary atmosphere formation

Outgassing from volcanoes, comet and asteroid impacts deliver ice

Terrestrial planet atmospheres all started out with _, _, and _ atmospheres

CO2, N2, and H2O

Evolution of terrestrial planet atmosphere is driven by _ effects

3

Effect 1 (evolution of terrestrial planets)

Greenhouse: solar heating/cooling balance, determines state of water

Effect 2 (evolution of terrestrial planets)

Planetary gravity: ability to retain atoms and molecules in its atmosphere

Effect 3 (evolution of terrestrial planets)

Chemistry of H2O and CO2: CO2 is easily dissolved in liquid H2O, carbon cycle regulates atmospheric CO2 and its contribution to greenhouse warming

Mercury started

Badly, low mass, close to sun, gravity too weak to keep atmosphere, now has no volcanoes and few impacts and no atmosphere today

The greenhouse effect makes a planet’s surface (warmer/cooler) than it would be if it had no atmosphere

Warmer

Warmer air = _ evaporation, warm air holds (more/less) water vapor

More, more

Water water vapor = (stronger/weaker) greenhouse effect = (warmer/cooler) air temp

Stronger, warmer

why did venus experience a runaway greenhouse effect

No CO2 cycle to regulate climate

The ability of a planet to retain atmospheric gases depends on the planets _ and _

Mass, temperature

Temperature determines how _ particles are moving. Higher temperature equals _ particles

Fast, faster

Fast particles are capable of escaping the planet if _

temperature is hot enough

Why can’t mercury retain an atmosphere?

It’s too hot and it’s gravity is too weak (too small)

What kind of atmosphere can mercury have sometimes (but cannot hold onto long term)?

Primordial due to H and He captured from protoplanetary disc

Today mercury has _ volcanoes, and _ impacts

No, few

Venus started too _ for liquid water

Hot

Venus’ oceans _ as sun became more luminous, what was the result?

evaporated, all water dissociated, H2 escaped into space, O reacted with other gasses —> runaway greenhouse effect, result in a dry hot heavy CO2 atmosphere

Earth started warm enough for _ and massive enough to keep a _

Liquid water, atmosphere

Mars was/wasnt warm enough for liquid water for first Gry

Was

Mars’ geological activity shut down as it cooled. Effects:

The atmosphere thinned, now has cold dry thin CO2 atmosphere (may have been hospitable in the past)

If mars was more _ it would be habitable today

Massive

Present day earth atmospheric element levels and temp

N2=77%

O2=21%

H2O=1%

Temp: 287°K

Present day venus atmospheric element levels

CO2: 96%

N2: 3.5%

Temp: 750°K

Present day Mars atmospheric element levels

CO2: 95%

N²: 2.7%

Ar: 1.6%

Temp: 220%

Ch 20!

Habitability in the solar system

Assume _ is required for life in the solar system — meaning needs to be perfect distance from sun and perfect size to have geological activity for an atmosphere

A liquid solvent (water)

Equilibrium surface temperature is set by

Distance from sun, albedo, atmosphere (greenhouse gasses trap heat and make surface warmer)

Best places to look for life in the solar system

Mars and Jovian moons: Titan, Europa and Enceladus

Albedo

Reflective surfaces that absorb less sunlight — colder

Basic requirements of life

1) source of energy, elements heavier than H and He (like Carbon) to build complex molecules, a liquid solvent medium for complex chemistry to occur, protection from UV

Largest source if energy in the solar system

Fusion in the sun

Amount of energy from the sun depends on

distance

If planets had the same reflectivity, planets closer to the sun will have (greater/smaller) equilibrium temperatures than those farther away

Greater

More distant objects are

cooler

Reflective objects are (hotter/cooler)

Cooler

Albedo (Ab) near 0 means

Not shiny/reflective

Albedo (Ab) near 1 means

Super shiny/reflective

If the moon had an atmosphere its surface temp would _ relative to its current surface

Increace

What life (Extremophiles) on earth remind us that sunlight isnt the only energy source

Hot life (energy from heat) and dark life (energy from reactions)

The temperature from solar heating depends on objects _ from the sun and how _ it is

Distance, reflective

What part of a planet is necessary for habitability? (Planet must be geologically active)

Internal heat

Why is water the ideal solvent for the chemistry of life?

Abundance, most organics dissolve in water, large heat capacity, floats when frozen, high surface tension, large range for being liquid

a small hot planet’s atmosphere

Gravity is too weak to hold onto atmosphere (must be very cold)