Conversations with the Earth Tom Burbine [e-mail]

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Conversations with the EarthTom
Burbinetburbine_at_framingham.edu
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Quiz on Thursday

• Moon
• Mars

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Need to account for these things when you form
the Moon

• The Moon's low density (3.3 g/cm3) shows that it
  does not have a substantial iron core like the
  Earth does.
• Moon rocks contain few volatile substances (e.g.
  water), which implies extra baking of the lunar
  surface relative to that of Earth.
• The relative abundance of oxygen isotopes on
  Earth and on the Moon are identical, which
  suggests that the Earth and Moon formed at the
  same distance from the Sun.

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Oxygen Isotopes

• There are three stable isotopes of oxygen
• They have masses of 16, 17, and 18 atomic mass
  units
• 16O 99.762
• 17O 0.038
• 18O 0.200
• The oxygen isotopic ratios (17O /16O and 18O/16O
  of silicate rocks from the Earth and Moon are the
  same and are different from most meteorites and
  Mars

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Geologic Time Scale

• A scheme to relate stratigraphy to time

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Why is there such a large age difference between
the beginning and end of the Cambrian?
Ma million years
http//geomaps.wr.usgs.gov/socal/geology/geologic_
history/images/geologic_time_scale.jpg
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• Cambrian is the earliest period where rocks are
  found with numerous large multicellular organisms
  that could be found as fossils

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http//pubs.usgs.gov/gip/geotime/fossils.html
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http//creationwiki.org/pool/images/thumb/c/c5/Evo
lution_timeline.jpg/400px-Evolution_timeline.jpg
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http//www.cityastronomy.com/geologic-earth-moon-g
raphic.bmp
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http//www.psrd.hawaii.edu/WebImg/LunarTimeScale.g
if
http//www.etsu.edu/physics/etsuobs/starprty/21200
mwc/moonmap.jpg
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Mars
http//www.daviddarling.info/images/Mars_large.jpg
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Mars

• Names after Mars, Roman God of War
• Mars has two tiny natural moons, Phobos and
  Deimos, which orbit very close to the planet and
  are thought to be captured asteroids.
• Both satellites were discovered in 1877 by Asaph
  Hall, and are named after the characters Phobos
  (panic/fear) and Deimos (terror/dread) who, in
  Greek mythology, accompanied their father Ares,
  God of War

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Percival Lowell (1855-1916)

• Lowell produced intricate drawings of the Red
  Planet
• Finding hundreds of straight lines (termed
  "canals")

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He thought

• Lowell concluded that the bright areas were
  deserts and the dark were patches of vegetation
• Lowell thought the canals were constructed by
  intelligent beings who once flourished on Mars.

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For years

• People thought life could exist on Mars and
  Venus, the closest planets to Earth

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However,

• Venus is extremely hot (700-800 K)
• Atmospheric pressure is 90 times that of Earth

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What happened on October 30, 1938?
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What happened on October 30, 1938?

• http//sounds.mercurytheatre.info/mercury/381030.m
  p3

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Mars

• The average recorded temperature on Mars is
  -63 C with a maximum temperature of 20 C and a
  minimum of -140 C
• Atmospheric pressure is 1/100 of Earths
• Mars is often enveloped by planet-wide dust
  storms

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Dust Devils

• http//en.wikipedia.org/wiki/ImageMarsdustdevil2.
  gif

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Dust Devils

• Dust devils are smaller and weaker than tornadoes
• They are caused by convection on hot, calm summer
  days.
• Air near the surface becomes much warmer than the
  air above, creating an updraft.

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Key to Life

• All life on Earth depends on water
• So if you find water, you may find life

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Habitable Zone

• The region around a star in which planets could
  potentially have surface temperatures which
  liquid water could exist

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In the past

• Mars appeared to be warmer and wetter

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Atmospheres

• Layer of gases that surround a body with
  sufficient mass
• Gravity keeps the gases around the body

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Atmospheric Pressure

• Pressure due to the weight of air above the
  measurement point
• Pressure is force per unit area
• Standard atmosphere is defined as being precisely
  equal to 101,325 Pascals where a Pascal is 1 N/m2
• 1 bar 100,000 pascals
• Pressure in the solar nebula was 10-4-10-8 bars

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Phase Diagram
http//img.search.com/thumb/d/dc/Phase-diag.png/30
0px-Phase-diag.png
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Mars
http//science.nasa.gov/headlines/y2000/ast29jun_1
m.htm
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http//images.encarta.msn.com/xrefmedia/aencmed/ta
rgets/illus/cha/T073590A.gif
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Pressure
Temperature
http//www.splung.com/heat/images/phases/phasediag
ram.png
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Any Questions?