ast final chapter 9

primary atmosphere

New planets formed primary atmospheres by sweeping up gas in the accretion disk. All terrestrial bodies lost their primary atmospheres because their gravity wasn't strong enough. Gases can escape relatively easily from a planet (their mean velocities are greater than the escape velocity) -The planets formed with thick primary atmospheres of H and He.

Which planets still have a primary atmosphere?

Only the outer gas planets.

mars atmosphere

Polar caps of ice and CO2, vast red deserts with craters and dunes, canyons, and dry river beds, ancient volcanoes, thin CO2 atmosphere

Where did the atmospheres of Earth, Mars, and Venus come from?

Secondary atmospheres were acquired later by: Volcanism (releasing the gas from the interior), Comet impact, Life! (on Earth)

tropopause

Temperature stops declining with altitude.

secondary atmospheres

atmospheres were acquired later by: -Accretion (but locked in the interior) -Volcanism (releasing the gas from the interior) -Comet impacts

Mercury and the Moon have

basically no atmosphere bc they are Small in mass, less gravity, could not retain atmosphere

what is climate change?Why are we worried about it here on Earth?

- in particular a change apparent from the mid to late 20th century onwards and attributed largely to the increased levels of atmospheric carbon dioxide produced by the use of fossil fuels. -The re-introduction of CO2 into the atmosphere could significantly affect the future of Earth's climate -The rise of CO2 , CH4 ,and other greenhouse gases is correlated with global temperature increase. ▪ The vast majority of climatologists accept the computer models suggesting the beginning of a longterm change in the temperature of Earth's climate. -raising sea levels - effected habitats of animals like seals and polar bears

stratosphere

-Temperature riseswith altitude. -Ozone absorbs UV light, heats stratosphere.

the moon and mercury are

-Almost totally airless. -Combination of high temperatures and low escape velocity means any atmosphere is lost. -No erosion from wind or other weathering, so the old and cratered surfaces are retained.

The Atmospheres Evolved Differently

-Mars and Venus both have mainly CO2 atmospheres. -Mars' atmosphere is much less dense than Venus', so no greenhouse effect on Mars. -Venus: larger planet, more volcanoes, bigger atmosphere, more greenhouse effect, higher escape velocity.

mesosphere

-No ozone, temperaturedeclines with altitude. -Upper mesosphere is coldest part of atmosphere.

troposphere

-Temperature and pressure decline with altitude. -Water vapor mainly here. -All the weather patterns that we experience happen here (due to convection)

If the planets started with the same atmosphere, why are they so different today?

-These planets differ in an important way: their gravity. -Venus and Earth were able to keep more gasses than Mars. -Venus has 2,500 times more atmospheric mass than Mars.

thermosphere

-Top of the thermosphere is called the ionosphere. -Ultraviolet radiation and solar wind can ionize atoms, causing the temperature to increase. -Solar wind = flow of particles from the Sun.

what is greenhouse gas

-is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. 96.5% CO2 (a Greenhouse gas). -primary greenhouse gases in Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone.

runaway greenhouse effect

-is a process in which a net positive feedback between surface temperature and atmospheric opacity increases the strength of the greenhouse effect on a planet until its oceans boil away. A • As on Earth, on Venus the early oceans kept the CO2 content down. • Once all the oceans were evaporated, CO2 accumulated in the atmosphere. • And the CO2 gas assisted in the runaway greenhouse effect.

Atmospheres of the Terrestrial Planets

All three were at some point volcanically active, and should have been hit by comets. The resulting secondary atmospheres are very different. These planets differ in their surface gravity.

venus atmosphere

Covered with deep sulfuric acid clouds in a dense CO2 atmosphere, hottest planet, immense volcanic peaks tower over desolate plains

Greenhouse Effect

Incoming sun heats the planet, outgoing infrared radiation cools the planet, some gases (especially CO2 and water vapor) block some infrared radiation, preventing the planet from cooling.

Why does Mercury have so little gas in its atmosphere?

It has a high temperature. It is close to the Sun. Its escape velocity is low. Its mass is small.

The main greenhouse gases in the atmospheres of the terrestrial planets are

carbon dioxide and water vapor

Venus and Earth were able to keep more ___ than Mars.

gases

Rank the layers of the atmosphere in order of height above the surface. highest first

ionsphere,thermosphere,mesosphere,stratosphere,troposphere

escape velocity

is the minimum speed needed for an object to escape from the gravitational influence of a massive body.

Arrange these four layers in ascending order, based on the temperature at the upper boundary of each. lowest first

mesosphere,troposphere,stratosphere,thermosphe

How does life impact the atmosphere of a planet?

on earth life further removed CO2 -Life is responsible for the oxygen in Earth's atmosphere

Terrestrial planets lost these

primaryatmospheres due to (1) being too small (not enough mass, less gravity) and too close to the Sun (too hot).

Venus, Earth, and Mars were able

to obtain and hold onto significant secondary atmospheres.

In what part of the atmosphere does weather occur in

troposphere

icehouse effect

• The amount of COAtmospheres of Earth & Mars 2 in the Earth's atmosphere is sustained by plate tectonics (volcanic eruptions). • When plate tectonics stopped on Mars, the volcanic source of CO2 shut down and rain would have removed O2 from the atmosphere. • As the amount of CO2 reduced, the temperature dropped and this caused more water vapor to condense and fall on to the surface taking some more CO2 , and further cooling Mars.