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