Download Mars: Early Studies (PowerPoint)

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 CO2 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 24h 37m
The polar caps contain frozen water and CO2 (dry ice).
Martians: Benign or Aggressive?
Is There Life on Mars?
Historically, lots of room for optimism:
generally ‘Earth-like’
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seasonal variations in colour (vegetation?)
climate
polar caps (water?)
atmosphere (albeit thin)
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
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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!]
Bodies of open water would simply
evaporate
The Red Planet
(Heinlein)
Meet Willis
H.G. Wells (1898)
War of the Worlds
Preamble:
http://www.astro.queensu.ca/~hanes/ASTR101-Fall2015/ANIMS/WoW-Intro.mp4
(This excerpt comes, incredibly enough,
from a 1978 ‘rock opera’ version of this
story produced by Jeff Wayne)
Our First Glimpse
http://www.astro.queensu.ca/~hanes/ASTR101-Fall2015/ANIMS/WoW-Seen.mp4
The War, and Our Victory
http://www.astro.queensu.ca/~hanes/ASTR101-Fall2015/ANIMS/WoW-Win.mp4
The Hallowe’en Hoax (1938)
(a different Welles)
Worth Pondering
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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.)
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Is inter-species infection a realistic worry?
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Read Michael Crichton’s ‘Andromeda Strain’
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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) 1971
1.
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 CO2
- could be somewhat thicker, lots of N2
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?
http://mars.jpl.nasa.gov/mgs/msss/camera/images/index.html
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? CO2
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.
4.
5.
GX (gas exchange) – CO2 in, what out?
LR (labelled release) – use a bit of radioactive
carbon in the ‘food’ to see if it reappears in
some other form (metabolic products)
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.
2.
Pictures: negative! (but no surprise)
GCMS – negative. No organic material AT ALL
found in the soil. Very discouraging.
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