Mars Astronomy 311 Professor Lee Carkner Lecture 14

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

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

Which of the following is not true about basalt and anorthosite? a)Basalt is found in the Maria b)Anorthosite is older than basalt c)Anorthosite is darker than basalt d)Basalt is similar to lava e)Basalt has more heavy elements

What best describes the Moon’s core? a)Large, solid, rocky b)Small, liquid, rocky c)Large, liquid, iron d)Small, liquid, iron e)Small, solid, iron

Mars Impactor Exercise  My data:  height = 50 cm = 0.5 m  crater diameter = 7 cm  mass of marble = 22.4 g = 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 = J/cm  for every J of energy in your impact the crater size increases by 1 cm

Mars -- The God of War  The red color of Mars led the Greeks and Romans to name it after the god of war 

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

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

Spacecraft to Mars  Mariner 4 was the first spacecraft to visit Mars in 1964   first high quality maps and surface images  Recent missions:   Spirit and Opportunity (2003, rover)  Phoenix (2008, lander)

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

The Surface of Mars  Mars is red due to iron oxide (rust) in the soil    Surface is covered with reddish soil and is rocky and broken

Temperature of Mars  We can estimate the average temperature of Mars from energy balance T M = [R S /(2 D S )] ½ T S   Mars is cold    Mars has seasons due to the tilt of its axis

Mars’s Atmosphere  Composition: 95% CO 2, 3% N 2, trace amounts of water vapor and oxygen  Pressure: 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

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  Frozen CO 2 also make up ice caps

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 could the water be now?    Mars may warm up periodically allowing water to form (Mars may now be in an ice age)

Dried-up River Bed

Past Water Erosion on Mars

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

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

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

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 

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

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

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

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