Mars
Astronomy 311Professor Lee
CarknerLecture 14
Mars -- The God of War
The Canals of Mars In 1877 G. Schiaparelli thought that he
saw intersecting straight lines on Mars
Percival Lowell built an observatory near Flagstaff, AZ and published elaborate maps of a network of canals and oasis on Mars
Mars Facts
Size: ~1/2 Earth size
Orbit: 1.5 AU
Description:
Celestial Motions of Mars
Mars rotates on its axis with a period of 24 1/2 hours
Mars has an orbital period of 23 months
Mars is tilted on its axis
Spacecraft to Mars Mariner 4 was the first spacecraft to
visit Mars in 1964
Recent missions: Mars Express (2003, orbiter) Mars Reconnaissance Orbiter (2006, orbiter) Spirit and Opportunity (2003, rover)
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
Dust storms alter the Martian craters
Tharsis Rise
Olympus Mons
Valles Marineris
Cratering on Mars
Mars Topological Map
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
Mars is cold Mars has seasons due to the tilt of its axis
Standing on Mars
Mars’s Atmosphere Composition: 95% CO2, 3% N2, trace
amounts of water vapor and oxygen Pressure: 0.007 atmospheres
Early Mars may have had a thicker
CO2 and H2O atmosphere
Water on Mars Mars is now a very dry world
Water ice may be present in the polar ice caps (along with frozen CO2)
It is possible that water exists
underground
Frost on Mars
Polar Ice Cap
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)
Dried-up River Bed
Past Water Erosion on Mars
Life on Mars? Mars shows evidence for liquid water and higher
temperatures in the past
Viking tested soil samples but the results were inconclusive
We do have a few meteors that were blasted off the surface of Mars
AH84001 shows some features that look a little like the remains of life-forms, but evidence is not very strong
Viking’s Soil Scoop
Fossil Life in Martian Meteorite?
Cydonia “Face” on Mars
Traits of Psuedoscience
Certainty
Avoidance of Occam’s Razor
Paranoia
Mars’s Interior Mars has a lower density than the other
terrestrial planets (4000 compared to 5000 kg/m3)
No evidence for plate tectonics We have very little other data on Mars’s
interior
Continuing Mars Exploration
Phoenix, a small “scout” lander mission, to be launched 2007
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 CO2, atmosphere cools
Water freezes
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 must 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