Atmospheres

Question 1

What is an atmosphere?

Answer 1

•layer of gas surrounding a planet
•generally thin around terrestrial planets
•causes weather

Question 2

What state do planetary atmospheres exist in?

Answer 2

Hydrostatic equilibrium

Question 3

Describe hydrostatic equilibrium

Answer 3

•held down by gravity
•held up by thermal motion of molecules

Question 4

Why are atmospheres critical to life?

Answer 4

•water is liquid owing to atmosphere pressure and temperature (mild greenhouse effect makes habitable)
•absorbs and scatters light( mainly blue)
•protects us from harmful UV radiation (ozone)
•protects us from cosmic rays and micro-meteorites
•oxygen for us to breathe, co2 for plants
•creates wind and weather

Question 5

Explain greenhouse effect

Answer 5

•radiation absorbed by planets surface, remit infrared slows rate of energy loss
•greenhouse gases optically thick in infrared

Question 6

How much does earths greenhouse effect increase average temperature?

Answer 6

31 degrees critical to raise it above freezing point

Question 7

What is the troposphere?

Answer 7

•lowest layer
•greenhouse effect and convection important
•temp drops with altitude

Question 8

What is stratosphere?

Answer 8

•begins when temp starts rising
•heated by Uv radiation

Question 9

What is thermosphere?

Answer 9

•high altitude temp rises again
•x rays and uv heat gas

Question 10

What is exosphere?

Answer 10

•atmosphere fades into space

Question 11

What are some sources of atmospheric gases?

Answer 11

•volcanic out-gassing (water and gases trapped in the interior during formation)
•evaporation or sublimation of surface liquids and ices
•micrometeorites and high energy particles (planets with significant atmospheres)

Question 12

Different losses of atmospheric gases

Answer 12

•condensation:gases condense to form surface liquids and solids
•chemical reactions:gases incorporated into surface metals or rocks
•impacts:atmospheric gases ejected into space
•solar wind:breaks molecules down into light elements
•thermal escape:gas has enough energy to escape into space

Question 13

Describe Mars atmosphere

Answer 13

•low atmospheric pressure( liquid water unstable)
•atmosphere could have been much denser in the past( many ancient volcanoes)
•primarily co2(lighter elements escaped)
•water and co2 trapped in ice caps and underground

Question 14

Why did Mars lose its atmosphere?

Answer 14

•no magnetic field, so no protective magnetosphere
•as it cooled molten core solidified ending convection that generates magnetic fields
•solar wind strips atmosphere, breaking apart molecules

Question 15

Does Mars have seasons?

Answer 15

Yes

Question 16

Why does Mars have more extreme seasons in southern hemisphere?

Answer 16

It’s elliptical orbit means it’s closer to sun during southern summer

Question 17

What happens to co2 on either Mars poles?

Answer 17

•freezes to dry ice at winter pole, and evaporates at summer pole
•strong pole to pole winds so extreme dust storms

Question 18

What was Venus’s original atmosphere similar to?

Answer 18

Earth’s

Question 19

What is Venus’s current atmosphere?

Answer 19

•high surface pressure
•very high temperature
•almost entirely co2
•extremely dense near surface
•scatters almost all blue light

Question 20

What happened to Venus’s atmosphere?

Answer 20

Runaway greenhouse effect