Theme 11– Mars: Early Studies ASTR 101 Prof. Dave Hanes

Mars and Its Tiny Moons

Mars vs Earth Mars has 11% of the mass of the Earth and 53% of its radius, so is similar in density (rocky) but has only 38% as strong gravity. It has thus retained only a very thin CO 2 atmosphere. It is 50% farther from the Sun, so is cooler and has a longer orbital period (1.88 Earth years). It spins on its axis once every 24 h 37 m The polar caps contain frozen water and CO 2 (dry ice).

Martians: Benign or Aggressive?

Is There Life on Mars? Historically, lots of room for optimism: generally ‘Earth-like’ seasonal variations in colour (vegetation?) seasonal variations in colour (vegetation?) climate climate polar caps (water?) polar caps (water?) atmosphere (albeit thin) atmosphere (albeit thin)

Canals! Canals!

Canali! Schiaparelli, 1877 opposition “We are inclined to believe them to be produced by an evolution of the planet, just as on the Earth we have the English Channel and the Channel of Mozambique…”

Meet Percival Lowell

The Benign Interpretation

Problems A structure equivalent to the Suez Canal would be unobservable from Earth [PL: but what if it were flanked by vast tracts of irrigated land?] A structure equivalent to the Suez Canal would be unobservable from Earth [PL: but what if it were flanked by vast tracts of irrigated land?] No one else could see them! [PL: not as good a telescope, site, or observer!] No one else could see them! [PL: not as good a telescope, site, or observer!] Bodies of open water would simply evaporate Bodies of open water would simply evaporate

The Red Planet (Heinlein) Meet Willis

H.G. Wells (1898) War of the Worlds Preamble: (This excerpt comes, incredibly enough, from a 1978 ‘rock opera’ version of this story produced by Jeff Wayne)

Our First Glimpse

The War, and Our Victory

The Hallowe’en Hoax (1938) (a different Welles)

Worth Pondering A lesson for our time: infection, etc. A lesson for our time: infection, etc. (Think about the First Nations experience in North America after the arrival of Europeans carrying smallpox and other diseases.) Is inter-species infection a realistic worry? Is inter-species infection a realistic worry? Read Michael Crichton’s ‘Andromeda Strain’ Read Michael Crichton’s ‘Andromeda Strain’ Do we have a right to enter new biospheres? Do we have a right to enter new biospheres?

Welcome Back From the Moon

Modern Explorations of Mars: Progress in Our Capabilities 1. remote sensing (telescopes, etc) 2. fly-by missions (quick snapshots) ~1960’s 3. orbiters (more detailed, better coverage) landers (sample the surface directly) 1976

Telescopic Too little detail of surface seen Atmospheric nature not well determined: “Blinking out” of stars  thin atmosphere - could be thin, pure CO 2 - could be thin, pure CO 2 - could be somewhat thicker, lots of N 2 - could be somewhat thicker, lots of N 2

Fly-by Missions (mid 60’s)

Hopes Dashed Atmosphere very thin! (no Nitrogen) No liquid water possible Barren, lunar landscape

Mariner 9 (1971) The first spacecraft to orbit another planet Arrived during a global dust storm; fortunately, the control gases lasted long enough! Photos of the moons of Mars: Phobos and Deimos Waiting patiently until…

First Discovery: Olympus Mons

Valles Marineris

Ancient Riverbeds?

Sand Dunes

Polar Caps

Faces on Mars?

Optimism Rekindled! Volcanoes  outgassing, and a once-thicker atmosphere? Incipient plate tectonics (Valles Marineris: a rift)  geophysical activity Ancient riverbeds? Perhaps copious water at one time?

So: Search for Life! The Viking Landers (1976) Experiment limited to ~1 cubic foot (a ‘milk crate’), limited in mass and technology Assume “Life As We Know It” (LAWKI): - carbon-based - needing water as a solvent - more likely to be small than large

Two Sites at Low Elevation

Five Tests for Life 1. Take a picture!

Seurat

2. Habeas Corpus (find the body) Search for organic material in the soil using GCMS (Gas Chromatograph / Mass Spectrometer). On Earth, we find such material everywhere! (even Antarctic ice cap)

Tests 3-5: Encourage enhanced bio-activity in (possibly dormant) life forms. (“Revive the mouse.”)

Revive the Mouse! (i.e. microbes in soil samples) Give it air, water, food, warmth! Look for signs of metabolism. What air? CO 2 Why water? LAWKI What food? Basic amino acids, sugars,… What would the mouse do (on Earth)? Breathe in oxygen, breathe out carbon dioxide. Consume simple foods and convert them to other organic ‘waste products’

The Apparatus

Three Martian Metabolic Experiments (add air, water, warmth, nutrients) 3. GX (gas exchange) – CO 2 in, what out? 4. LR (labelled release) – use a bit of radioactive carbon in the ‘food’ to see if it reappears in some other form (metabolic products) 5. PR (pyrolytic release) – after the experiment, heat the sample to drive off and search for any new compounds (metabolic products)

Results of All Five Experiments 1. Pictures: negative! (but no surprise) 2. GCMS – negative. No organic material AT ALL found in the soil. Very discouraging. Tests 3,4,5 all gave positive results Tests 3,4,5 all gave positive results - but with some surprising inconsistencies!

Example: LR Why do increased nutrients lead to a fall-off of ‘metabolic’ behaviour?

The Present Interpretation [still some controversy] We were probably seeing purely chemical reactions, not metabolic behaviour The Martian surface is strongly ‘bleached’ by solar ultraviolet light (the planet has no protective ozone layer). Hence the lack of organic material. The soil is also apparently rich in hydrogen peroxide, explaining some of the chemistry