1. Mars Astronomy 311 Professor Lee Carkner Lecture 14

2. Which best describes the surface of the Moon? a)Uniformly covered with craters b)Rough on the near side and smooth on the far side c)Older terrain in the highlands and younger terrain in the Maria d)Covered with lava from volcanic eruptions e)Covered in iron-rich dust

3. What is one reason that we think the Moon was formed via impact? a)We find evidence of the impact crater under the Yucatan peninsula b)Moon rocks are similar to earth rocks c)The Maria must have been formed by a giant impact d)Only a giant impact could produce the Moon’s tidal locking e)The large amount of oxygen in lunar soil must be due to an impact

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

5. The Canals of Mars  In 1877 G. Schiaparelli thought that he saw intersecting straight lines on Mars   This was translated to English as “canals” implying that somebody built them   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:   Mars Odyssey (2001, orbiter)   Mars Reconnaissance Orbiter (2006, orbiter)   Spirit and Opportunity (2003, rover)

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  Mars is red due to iron oxide (rust) in the soil   Dust storms sometimes cover large fractions of the surface   Mars is cold   180 K at night (-135 F)  Mars has seasons due to the tilt of its axis

10. Your Weight on Mars  Three things effect how much you weigh:     Note that weight is a force  We can translate the force on you in pounds into your mass in kilograms, since we know the properties of the Earth

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. Water on Mars  Mars is now a very dry world   A pan of water left out on Mars would boil   It is possible that water exists underground

13. Was Mars Wet?  Surface features indicate that water once flowed freely on the Martian surface   Due to:  Global water (Many oceans, rivers, etc)?   Mars may have been warmer with a thicker atmosphere in the past   Where is the water now?    Mars may warm up periodically allowing water to form (Mars may now be in an ice age)

14. Life on Mars?  Mars shows evidence for liquid water and higher temperatures in the past   Could that life have survived?   If life was microscopic it might be hard to find

15. Traits of Psuedoscience  Certainty   Avoidance of Occam’s Razor   Paranoia  Any problems with the theory are someone else’s fault (e.g. government cover-ups)

16. 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

17. Future Mars Exploration  The Phoenix lander was launched August 2007   Mars Science Laboratory, a large, long- duration rover planned for 2009  Sample return?   Manned mission? 

18. A Possible History of Mars  Mars forms  Mars is cratered   CO 2 greenhouse keeps Mars warm, liquid water flows  Mars losses internal heat, crust cools    Atmosphere loses CO 2, atmosphere cools  Lava flows stop 

19. Next Time  Read Chapter 14.1 and 14.4  No class Friday  Quiz 2 next Monday  Observing Tomorrow (Tuesday) 8-9 pm  Only if you missed the last one

20. 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

21. 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

22. 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