1. Mars Astronomy 311 Professor Lee Carkner Lecture 14

2. Moon Impactor Exercise  My data:  height = 50 cm = 0.5 m  crater diameter = 7 cm  mass of marble = 22.4 g = 0.0224 kg  Energy  PE = mgh = (0.0224)(9.8)(0.5) = 0.11 J  Velocity  v = (2gh) ½ = [(2)(9.8)(0.5)] ½ = 3.13 m/s  Energy-crater size relationship  energy/crater size = 0.11 J / 7 cm = 0.016 J/cm  for every 0.016 J of energy in your impact the crater size increases by 1 cm  Does not seem to hold for any height

3. Quiz #2 on Friday  Quiz 2 similar format as Quiz 1  ~20 multiple choice/matching  ~4 short answer  Covers lectures 9-15  bring pencil and calculator  Study guide on web page  Jupiter observations due Wednesday

4. Mars -- The God of War   Shows color more strongly than other planets

5. The Canals of Mars   He called them canali, Italian for “channels”   Percival Lowell built an observatory near Flagstaff, AZ and published elaborate maps of a network of canals and oasis on Mars  Mars was thought to be very dry, so naturally the inhabitants needed to carefully manage water

6. Mars Facts  Size: ~1/2 Earth size   Orbit: 1.5 AU   Description: red, dusty, thin atmosphere

7. Spacecraft to Mars   Viking 1 and 2 (1975) extensively imaged Mars and also sent landers to the surface   Recent missions:   Spirit and Opportunity (2003, rover)  Phoenix (2008, lander)

8. Surface Features  Volcanoes -- Mars has many shield volcanoes, but they are not active today   Canyons -- Mars shows deep canyons, the result of volcanic activity stressing the crust   Craters --The northern hemisphere is less heavily cratered than the southern  Why?    Dust storms alter the Martian craters

9. The Surface of Mars   Red dust in atmosphere gives sky a pink tint   Surface is covered with reddish soil and is rocky and broken

10. Temperature of Mars  T M = [R S /(2 D S )] ½ T S  Assumes that Mars absorbs all sunlight incident upon it and then radiates the energy freely back into space  Mars is cold    Mars has seasons due to the tilt of its axis

11. Mars’s Atmosphere   Pressure: 0.007 atmospheres   Early Mars may have had a thicker CO 2 and H 2 O atmosphere   Mars has no plate tectonics to return the CO 2 to the atmosphere

12. Volatiles on Mars  Water cannot exist on the surface of Mars as liquid   Even though it is very cold, the low atmospheric pressure makes it easy for water to “escape” the liquid form into a gas   Carbon dioxide frost 

13. Was Mars Wet?  Surface features indicate that water once flowed freely on the Martian surface   Due to:   Spot flooding (water frozen underground and sometimes comes to the surface)?   Most likely due to a greenhouse effect  Where could the water be now?   In the polar caps  Mars may warm up periodically allowing water to form (Mars may now be in an ice age)

14. Life on Mars?   Could life have formed on Mars when it was wetter?  Could that life have survived?   If life was microscopic it might be hard to find

15. Mars’s Interior  Mars has a lower density than the other terrestrial planets (4000 compared to 5000 kg/m 3 )   No evidence for plate tectonics   There are no seismometers on Mars  Mars may have only a small solid iron core or no iron core at all

16. Future Mars Exploration   large, long-duration rover   MAVEN (Mars Atmosphere and Volatile EvolutioN) orbiter planed for 2013  Sample return?   Manned mission? 

17. A Possible History of Mars  Mars forms   Volcanism creates volcanoes and lava flows   Mars losses internal heat, crust cools    Atmosphere loses CO 2, atmosphere cools  Lava flows stop 

18. Next Time  Read Chapter 14.1 and 14.4

19. Summary  Red, dusty, thin atmosphere  Mars is a medium-sized world allowing it to retain an atmosphere (unlike Mercury and the Moon), but not a thick atmosphere (like Venus and Earth)  Mars shows signs of being habitable in the past, but no good evidence of life has been found

20. Summary: Surface  Mars has a red surface composed of dust, soil and rocks  Mars has large volcanoes and deep chasms  Dust storms often cover the surface  Mars has a low density and may not have an iron core

21. Summary: Climate  Mars has a very thin atmosphere and is cold  Low temperature and pressure prevent liquid water on the surface  Mars may have had a thicker, warmer atmosphere in the past since there is substantial evidence for water flows  Early thicker CO 2 greenhouse atmosphere gradually washed out by rainfall  The temperature on Mars may change over time due to orbital variations