Mars

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

3
Mars -- The God of War

• Shows color more strongly than other planets

4
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

5
Mars Facts

• Size 1/2 Earth size
• Orbit 1.5 AU
• Description red, dusty, thin atmosphere

6
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)

7
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

8
The Surface of Mars

• Red dust in atmosphere gives sky a pink tint
• Surface is covered with reddish soil and is rocky
  and broken

9
Temperature of Mars

• TM RS/(2 DS)½ TS
• 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

10
Marss Atmosphere

• Pressure 0.007 atmospheres
• Early Mars may have had a thicker CO2 and H2O
  atmosphere
• Mars has no plate tectonics to return the CO2 to
  the atmosphere

11
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

12
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)

13
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

14
Marss Interior

• Mars has a lower density than the other
  terrestrial planets (4000 compared to 5000 kg/m3)
• 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

15
Future Mars Exploration

• MAVEN (Mars Atmosphere and Volatile EvolutioN)
  orbiter planed for 2013
• Sample return?
• Manned mission?

16
A Possible History of Mars

• Mars forms
• Volcanism creates volcanoes and lava flows
• Mars losses internal heat, crust cools

• Atmosphere loses CO2, atmosphere cools
• Lava flows stop

17
Next Time

• Read Chapter 14.1 and 14.4
• Quiz 2 on Friday
• Same basic format as Quiz 1, plus some matching
  questions

18
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

19
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

20
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 CO2 greenhouse atmosphere gradually
  washed out by rainfall
• The temperature on Mars may change over time due
  to orbital variations