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Flashcards in Lecture 6 Deck (29):

Percival Lowell's study of Mars

-good place to study earth
-light patches and dark patches on map that change shape during the year
-the poles also melt and come back throughout the year
-Lowell's map is based on the detailed images he saw through a telescope (1908)
-looked very closely and could see lines on the planet that he denoted as canals
-concluded that these were signs of intelligence on mars that made these systems of water to transport things and that the dark patches were signs of plant growth
-pretty widely accepted view into the 20th century


H.G. Wells

-Used Lowell's interpretation of the planet to write his book The War of the Worlds
-depicted the intelligent life as evil
-transformed into a radio show later that caused a panic because they took it more seriously than intended.


C.S. Lewis

-Out of the Silent Planet
-different view of Martians
-they're the good ones and humans are evil but can possibly be redeemed.
-creates a Martian ecology in writing this novel
-makes up names for all the topography, zoology, and the botany.


Different constructs of martians due to our fears and desires

1. Martian-invader: powerful and evil
2. Kindly ones: higher purpose for us
3. Ironic ones: Kurt Vonnegut's Sirens of Titan-->turns out to have manipulated all of Earth's history
4. Unimaginably different ones: Stanislaw Lem's Solaris-->Whole planet is alive that communicates with the scientists...?


NASA changed our view of Mars

-dark spots weren't vegetation, but craters
-word was slow to get out-->Quote by Vice President Dan Quayle as Chairman of the National Space Council


Valles Marineris

-Canyon in mars is largest canyon in the solar system-->much bigger than the grand canyon probably made by some plate tectonic event
-most craters from meteors


Mars and Earth's similar features

1. Both rocky (close together)
2. Active geologically
3. Have atmospheres (Mars is thinner)
4. Have water and surface effects of water
5. Both have potential for life to have evolved
6. Mars still has early Precambrian surface lost to erosion and geologic forces on Earth
-Mars is the closest possibility to see if life is unique to Earth


Dealing with mars is a little difficult

-small size and distance from Sun
-gravity is only 37% of Earth
-most of original atmospher-N2 and CO2 and Water have departed via solar wind (core has frozen...? ask about this)***
-dissociation of water by UV left lots of oxygen to oxidize the iron of the crust
-most remaining water is ice
-rovers and satellites seek (and find) geological evidence of surface water
-Phoenix Lander looked for subsoil ice directly-has remnants of glaciers
-rover being developed to look for life on planet


Mars isn't very lively now but ask if life existed when planet was young

1. How long did it have a dense atmosphere? Any free O2?
Was the temperature ever above freezing?
2. Did it have free flowing neutral water on the surface?
3. Were organic compounds related to life available?
4. Is there direct evidence of life?


Mars vs. Earth's timelines

-Mars preserves a record from 4.5 byr to 3.7 byr lost on earth because of out planets active geology


Opportunity at Victoria Crater

-one of the most interesting places the rover visited
-finds that there was flowing water in the deep past because of hematite "blueberries" which need water to form and water deposited strata in Martina crate wall


Gale crater

-hump in the center is because of all the wind and erosion that it excavated out some of the sediment that had been deposited by flowing water and wind.
-reconstruction shows that it was a major body of water
-Clay/Shale layer important because it shows that it has an environment that can support life if this rock can be formed


Water on Mars

-There was flowing water in the deep past! Unfortunately,
the surface at the Opportunity site represents a late stage
of free water on Mars, when high sulfate levels made the
water a highly acidic brine
-Other sites with older geology from before the drying out
of the planet were sought.
-The Curiosity rover mission was aimed at a site in a
crater that has signs of surface water and rock
deposits from an earlier time. Curiosity landed in Gale
Crater in 2012 to inspect the older geology.


Life under Earth's crust

-full of life under the crust some as much as 3 miles under the ground (diamond and gold mines in Africa)
-look into walls and they're full of bacteria-->as could be the case on mars


Gale crater geological section

-We don't have the rocks on Earth like those on Mars to make such a comparison. They existed at one point in time but we don't have access to them now.


Oxygen on Mars

-had oxygen in its atmosphere before 3.5 bya
-oxidation is what gave Mars its color
-likely that the planet was wet, warm and rusty billions of years before Earth's atmosphere became oxygen rich


Microbes and methane on Mars

-Seeing methane on mars doesn't mean that there are microbes making it, it just seems questionable
-When a meteor hits Mars the parts fly off into the atmosphere and into space so it could be possible that microbes from mars ended up on earth after traveling through the solar system and thus starting life on Earth. There is no way of knowing


Direct searches for life on Mars

-Viking 2 lab landed on Mars in 1976 with experiments to
search for metabolic events and organic carbon. Metabolic
experiments ambiguous. No organic carbon found.
-Phoenix lab 2008 at Mars North polar region. Found ice
and water, no organics detected yet. Peroxides on surface-destructive to organics.
-NASA 2009 - significant release of methane, not
reproducible in 2012. Organics in Mars-derived meteorites
are not of biotic origin.
-Curiosity has found organic compounds


Why life can currently be on Mars

-surfaces is cold, dry, oxidizing, and blasted with UV
-could have possibly existed but is now extinct


Why are the organic compounds detected all chlorinated?

-It is because present day Mars is so oxidized.Heating of organic samples in Mars rocks reacts with perchlorate to give the chlorinated forms.


How Doppler works

-Planet going around the star, the star doesn't stay still in the middle but is also moving (by a matter of a few feet) but is still observable.
-can see if some star is wobbling because of some unseen planet moving around it.


Transit Method

-can see the planet go across the face of the star which cuts the light the star is emitting but just a little bit which can be recorded.
-used by Kepler


Substances we believe need to be present to support life

-water: required by all life
-methane: implies organic molecules are being processed by chemistry
-free oxygen: process like photosynthesis that is breaking down CO2



-made by live algae
-go way back in the fossil record
-best chance of Curiosity spotting a fossil remain on mars would to be something like this.


Methods for finding extra-solar planets

-direct imaging


Formation of our solar system/planets

-4.6 bya
-early-->sun surrounded by disc of dust
-later planets condense from clumping of smaller particles
-Earth, Venus, Mars, Mercury are rocky planets formed by accretion of inner solar material, more rich in heavier elements


Birth of Earth

1. Accretion ca 4.6 bya
2. Collision of proto-Earth with a Mars-sized protoplanet
blows off a mass of Earth’s outer layers. That becomes
the Moon.
3. A period of impacts with objects of various sizes, some
large enough to melt the surface of the planet.
4. By about 4 bya, era of collisions ends (still see the scars
on the Moon). Atmosphere and oceans form. Much
water and organic compounds delivered by collisions
with comets.
5. Origin of life by about 3.7 bya.


Origins of organic compounds

Two sources -
1. Brought in by comets and meteors (the Murchison
meteor is 5% organic compounds, including several
amino acids).
2. Synthesis by energy sources acting on precursors in the
atmosphere and oceans.
3. Most common elements in the universe -
H, C, O, N. These are the main components of life.


Life left chemical fossils that reveal metabolsim

-First life on Earth was made up of bacteria and archaea
-The first 2 billion years of life Earth had no O2
-Life left fossils of large layered fossils of
microbial mats - stromatolites
-Early life left fossils of individual cells