AST101 Lecture 17

Barsoom There are 4 Terrestrial Planets

• • • Earth • Mercury

From the Messenger Orbiter, March 2011.

Rayed crater: Debussy Venus

From the Venus Express, 2007.

H2SO4 clouds Earth (Terra)

Apollo 17 Mars

Hubble Space Telescope Barsoom

A world like our own? Populated by aliens? Telescopic Observations

Mars is dynamic • Polar caps wax and wane • Surface features change shape regularly • Clouds obscure the surface

Giovanni Schiaparelli Published a map of Mars in 1877 Identified surface features he called “canali” Schiaparelli’s Mars Percival

Mistranslated “canali” (channels) as canals Established Lowell Observatory on Mars Hill, Flagstaff AZ Lowell’s map of Mars (excerpt) Lowell’s Mars

Canals imply • intelligent life, and • deliberate construction

Lowell created a Mars that is • a dying planet, • whose intelligent denizens built canals – to collect the melting polar ice, and – to distribute the water among the oases (1884) Chesley Bonestell: Surface of Mars © Bonestell Space Art No one would have believed in the last years of the nineteenth century that this world was being watched keenly and closely by intelligences greater than man's and yet as mortal as his own; that as men busied themselves about their various concerns they were scrutinised and studied, perhaps almost as narrowly as a man with a microscope might scrutinise the transient creatures that swarm and multiply in a drop of water. H. G. Illusions of Mars. I.

This mythos arose from two optical illusions.

1. The human brain tends to connect the dots, which results in apparent linear features. 2. Dark grey, when viewed next to red, appears .

Mars is not a red planet with green vegetation outlining water canals. Mars is a red planet with dark grey regions.

The Dream is Smashed

Mariner 4, 1965 6, 1967 Mariner 9, 1969 Meridiani Sinus and Rilles in Mare Deucalionis Regio Sirenum Mars Today

Valles Marineris and the Ridge Schiaparelli Hemisphere

Hellas Basin Northern Polar Cap in Spring Weather Severe Weather

A Dust Devil A Frosty Morning In July 1976

Viking 2 Roaming on the Surface

Dried Riverbeds

Snow on Mars Phoenix

May 25 2008: Landing on a patch of ice. Sedimentation? Sedi- mentary Rocks Crater Hematite Concretions Fossil Icebergs? Curiosity on Mars

Gale Crater

Wall of Crater

Science Highlights

• NASA Rover Finds Conditions Once Suited for Ancient • NASA Rover Finds Old Streambed on Surface • NASA Rover Finds Clues to Changes in Mars' Atmosphere Illusions of Mars. II. A Face on Mars? The Face on Mars

More recent images with better cameras (MGO) More Illusions of Mars Life on Mars today?

• There is no macroscopic life • There is no permanently running water • The atmosphere is about 0.001 bar

• Mars today is old, cold, and dry Methane on Mars Methane on Mars Meteorites from Mars Are We the ?

• Mars was more hospitable to life early on • Mars had a significant atmosphere and surface water • Earth took longer to develop a solid surface

• How did microbial life evolve on Earth a mere 200 million years after the Earth's surface solidified? • Perhaps life evolved on Mars, and was carried to Earth on meteorites