1. Weather and Climate These are Earth’s global wind patterns or circulation - local weather systems move along with them -weather moves from W to E at mid- latitudes in N hemisphere Two factors cause these patterns - atmospheric heating - planetary rotation weather – short-term changes in wind, clouds, temperature, and pressure in an atmosphere at a given location climate – long-term average of the weather at a given location

2. Global Wind Patterns air heated more at equator - warm air rises at equator; heads for poles - cold air moves towards equator along the surface two circulation cells are created in each hemisphere cells do not go directly from pole to equator; air circulation is diverted by the Coriolis effect - moving objects veer right on a surface rotating counterclockwise - moving objects veer left on a surface rotating clockwise

3. Coriolis Force on Earth Animation Coriolis Force and Merry-go-Round Animation

5. Four Major Factors Which Affect Long-Term Climate Change

6. Gain/Loss Processes of Atmospheric Gas Unlike the Jovian planets, the terrestrials were too small to capture significant gas from the Solar nebula. - what gas they did capture was H and He, and it escaped -present-day atmospheres must have formed at a later time Sources of atmospheric gas: - outgassing – release of gas trapped in interior rock by volcanism - evaporation/sublimation – surface liquids or ices turn to gas when heated - bombardment – micrometeorites, Solar wind particles, or high-energy photons blast atoms/molecules out of surface rock - occurs only if the planet has no substantial atmosphere already

7. Gain/Loss Processes of Atmospheric Gas Ways to lose atmospheric gas: - condensation – gas turns into liquids or ices on the surface when cooled - chemical reactions – gas is bound into surface rocks or liquids - stripping – gas is knocked out of the upper atmosphere by Solar wind particles - impacts – a comet/asteroid collision with a planet can blast atmospheric gas into space - thermal escape – lightweight gas molecules are lost to space when they achieve escape velocity gas is lost forever!

9. Origin of the Terrestrial Atmospheres Venus, Earth, and Mars received their atmospheres through outgassing. - most common gases: H 2 O, CO 2, N 2, H 2 S, SO 2 Chemical reactions caused CO 2 on Earth to dissolve in oceans and go into carbonate rocks (like limestone.) - this occurred because H 2 O could exist in liquid state - N 2 was left as the dominant gas; O 2 was exhaled by plant life - as the dominant gas on Venus, CO 2 caused strong greenhouse effect Mars lost much of its atmosphere through impacts - less massive planet, lower escape velocity

10. Origin of the Terrestrial Atmospheres Lack of magnetospheres on Venus and Mars made stripping by the Solar wind significant. - further loss of atmosphere on Mars - dissociation of H 2 O, H 2 thermally escapes on Venus Gas and liquid/ice exchange occurs through condensation and evaporation/sublimation: - on Earth with H 2 O - on Mars with CO 2 Since Mercury and the Moon have no substantial atmosphere, fast particles and high- energy photons reach their surfaces -bombardment creates a rarified exosphere Ice recently discovered on Moon in craters near the poles - perpetually in shadow and frozen - probably came from impacts of ice-rich comets - possibly on Mercury too

11. Martian Weather Today Seasons on Mars are more extreme than on Earth -Mars’ orbit is more elliptical CO 2 condenses and sublimes at opposite poles - changes in atmospheric pressure drive pole-to-pole winds - sometimes cause huge dust storms

12. Martian Weather: N Polar Ice Cap and Dust Storm

13. Climate History of Mars More than 3 billion years ago, Mars must have had a thick CO 2 atmosphere and a strong greenhouse effect. - the so-called “warm and wet period” Eventually CO 2 was lost to space. - some gas was lost to impacts - cooling interior meant loss of magnetic field - Solar wind stripping removed gas Greenhouse effect weakened until Mars froze.

14. Venusian Weather Today Venus has no seasons to speak of. - rotation axis is nearly 90º to the ecliptic plane Venus has little wind at its surface - rotates very slowly, so there is no Coriolis effect The surface temperature stays constant all over Venus. - thick atmosphere distributes heat via two large circulation cells There is no rain on the surface. - it is too hot and Venus has almost no H 2 O Venusian clouds contain sulfuric acid! - implies recent volcanic outgassing?

15. Climate History of Venus Venus should have outgassed as much H 2 O as Earth. -Early on, when the Sun was dimmer, Venus may have had oceans of water Venus’ proximity to the Sun caused all H 2 O to evaporate. - H 2 O caused runaway greenhouse effect - surface heated to extreme temperature - UV photons from Sun dissociate H 2 O; H 2 escapes, O is stripped

16. If Earth Moved to Venus’ Orbit Today

17. Shaping Planetary Surfaces Four major geological processes that shape planetary surfaces: - impact cratering: excavation of surface by asteroids or comets striking the planet - volcanism: eruption of lava from interior - tectonics: disruption of lithosphere by internal stresses - erosion: wearing down by wind, water, ice

18. Terrestrial Planet Surfaces

19. Comparison of Planetary Surfaces Mercury & the Moon - heavily cratered {scars from the heavy bombardment} - some volcanic plains Venus - volcanoes and bizarre bulges Mars - volcanoes and canyons - apparently dry riverbeds {evidence for running water?} Earth - all of the above plus liquid water and life

20. Inside the Terrestrial Worlds After they formed, the molten planets differentiated into three zones: - core - made of metals - mantle - made of dense rock - crust - made of less dense rock Most of Earth’s interior is rock - only narrow region of upper mantle is molten rock - where lava comes from Interior layers also categorized by strength of rock which depends on composition, temperature, and surrounding pressure. Weaker rock can slowly deform and flow over millions of years. Why asteroids are irregularly shaped - weak gravity unable to overcome rigidity of rock. Gravity of larger world can overcome strength of solid rock, shaping it into a sphere - will shape anything over about 500 km in diameter into a sphere in about 1 billion years Lithosphere - the rigid, outer layer of crust and part of the mantle which does not deform easily - “floats” on softer rock beneath.

21. Inside the Terrestrial Worlds

22. Comparison of Terrestrial World Interiors active geology- Earth and Venus(?) still have molten cores inactive geology - the cores of Mercury, mars and the Moon have long since cooled and solidified

23. objects hit planet at 10 – 70 km/s (30,000 - 250,000 km/hr) - solid rock is vaporized - a crater about 10 times the size of the object and one to two times as deep is excavated Impact Cratering

24. matter is ejected in all directions - craters are circular -large craters have a central peak - like the way water rebounds in the center when you drop a pebble in it

25. Production of a Crater Animation

27. Counting Craters to find Surface Age Lunar highlands - crowded areas of cratering - rocks date to 4.4 billion years Lunar maria - huge impact basins filled in by lava flow - relatively few craters - rocks date to 3 - 3.9 billion years Heavy bombardment must have subsided very early in solar system history Cratering rate decreased as Solar Systems aged. The older the surface, the more craters are present.

28. History of Cratering Animation