Welcome to Geosc 40, January 14th (Lecture 2)
The Nature of Scientific Inquiry and
The Origin of Water on Earth
Ocean Man;
Ween
Somewhere Beyond
the Sea, Robbie
Williams
Under the SeaThe Little Mermaid
Skizzy Mars Crash ft. Pell
Thanks to: Rachel B., Spencer C.,
Stephanie L., Noah K.
Geosciences 40: The Sea Around Us
Course Web Page: www3.geosc.psu.edu/geosc040
Geosciences 40: The Sea Around Us
Course Web Page: www3.geosc.psu.edu/geosc040
How is the class going to work?
What should I study?
The Nature of Scientific Inquiry and
The Origin of Water on Earth
Can the North Brazil Current Help Us Understand
Atlantic Water Flow?
Why the Sea is Salty
Seawater is essentially an NaCl solution
Average seawater salinity is 35 ppt (35 g/kg), but it varies
from place to place
30 ppt
Surface water salinity
37 ppt
Water reservoirs
The oceans contain nearly all
of Earth's surface water (>97%)
• lakes & rivers = 0.01% of available water
• ice (glaciers and ice caps) & groundwater = 2.5%
• atmosphere (water vapor) = <0.001%
Ah, but the oceans contain only a small portion of Earth’s total water -most of Earth’s water is in its interior!
Origin of Water in the Oceans
How Science Gets Done
And How Concepts Evolve
The Scientific Method is Based
on Empirical Observations,
Skepticism and Repeated
Measurements
Belief-Based vs. Empirical
• Truth is based on authority (of texts, selfproclaimed or selected leaders, legends,
etc.) and is generally inviolable.
• Truth is based on application of a
standardized method and repeated tests to
confirm a result, and is subject to change as
new methods are developed and new results
discovered.
In other words, theories evolve…
Belief-based vs. empirical approaches to knowledge
Belief
system
The Source Of
Authority?
Definitions are simply decrees.
They are not based on Science
The Theory of Evolution is Based on
The Scientific Method
A theory based on
scientific principles
and rigorously tested
by skeptical scientists
for over a century and
a half!
Marone’s Theory of
Learning and Grades
• Come to class
• Read the
materials on the
course web site
• Be curious
• Ask questions
you’ll get an A in this
course and live
happily ever after…
Empirical* system:
Parameter “Y”
Measurements
Observations
Hypotheses
Theories
Parameter “X”
Scientific Method
“Correlations”
*empirical means “experiential” or “searching for interrelationships”
Scientific method: definitions
FACT : observation repeatedly confirmed
HYPOTHESIS: testable statement about the natural world
(a working model)
THEORY: a set of verified hypotheses that explain how
things work. A theory explains most or perhaps all of the
observations, but ‘the jury is still out,’ for one reason or
another.
LAW: generalization of how some aspect of natural
world behaves under stated circumstances;
repeatedly-verified explanation of some
aspect of the natural world
1. Initial observation of
materials/phenomena/behavior
THE SCIENTIFIC
METHOD
2. Development of questions/establishment
of constraints
3. Formulation of models to explain your
observations
MULTIPLE WORKING HYPOTHESES
4. Testing of hypotheses through
observation/experiment;
COLLECTION OF DATA (MEASUREMENTS)
5. Analysis of data, evaluation/interpretation
of results (ELIMINATE HYPOTHESES)
6. Formulate conclusions.
Scientific Method

Hypotheses and Theories must be falsifiable.

That is, we can never “prove” a hypothesis, we can
only disprove it

We must accept some uncertainty until substantial
observations and tests have been conducted.

Some problems do not yield easily and answers are
complex (for example--the origin of water on Earth;
the carbon cycle; global climate, earthquake
prediction
Chat with at least 3 people around you. Can
you set up a time to go over course
materials, study for exams or otherwise talk
about the materials in this course?
Does the person on your right live
A) On campus
B) Off campus
The Habitable Zone
Where did Earth’s Water Come
From? And Why is it Still Here?
Seawater Origin and Evolution
Where’s Pluto?
Earth: The Third Stone from the Sun (Jimi is not dead!)
• The chemical evolution of Earth’s ocean and atmosphere
is intimately related to the processes that formed the
Earth--the water planet.
• Why does Earth have liquid water whereas the other
planets do not at present? Or do they?
The “Goldilocks Principle”
http://www3.geosc.psu.edu/geosc040/40.lecture_files/
Planetary mass
Distance from sun
SURFACE
TEMPERATURE
ATMOSPHERIC
COMPOSITION
Boiling breaks
chem bonds
(°C)
100°
High gravity retains
light volatile gases =
thick atmosphere
Low gravity loses
all atmospheric
gases
0°
LIFE ZONE
*
Freezing stops
all biochem rxns
INTERNAL COMPOSITION
Because of a generous portion of radioactive elements the Earth retains a liquid outer
core (within Earth’s interior) of iron and nickel that provides a mechanism for generating
a protective magnetic field that shields the surface from harmful solar radiation.
WATER on MARS 4 BILLION YEARS AGO?
3000 km
The Grand Canyon of Mars - Valles Marineris
Water-formed gullies in crater
Photos and mosaic JPL/ NASA
NASA “Global Surveyor”
mission map of ancient oceans
on Mars (orbiter, 1997)
The Origin of Water on Earth
• Was it always here?
• What about in the earliest
stages of Earth’s history
• Have we always had the
same amount of water?
• Have the oceans always
been the same size?
• Has ocean water always
tasted the same?
• There’s a lot of water out there….
• Where did it come from?
Two Major Hypotheses
Earth Belch –degassing of volatile chemical species (water,
C02, etc. Substances easily driven off by heat
Volcanic Eruptions, Hot Springs, Seafloor Vents
E.T ? Comets and meteorites. Impacts big and small
Seawater Origin and Evolution
Is it a planet ?!
ET? Comet,
meteorite impact
So, Where Did the Oceans Come
From?
So, Where Did the Oceans Come
From?
So, Where Did the Oceans Come
From?
So, Where Did the Oceans Come
From?
So, Where Did the Oceans Come
From?
Summary: Origin of Water on Earth
and in the Oceans
Two Major Hypotheses
Earth Belch –degassing of volatile chemical species (water,
C02, etc. Substances easily driven off by heat
Volcanic Eruptions, Hot Springs, Seafloor Vents
E.T ? Comets and meteorites. Impacts big and small
The “Goldilocks Principle”
http://www3.geosc.psu.edu/geosc040/40.lecture_files/
Planetary mass
Distance from sun
SURFACE
TEMPERATURE
ATMOSPHERIC
COMPOSITION
Boiling breaks
chem bonds
(°C)
100°
High gravity retains
light volatile gases =
thick atmosphere
Low gravity loses
all atmospheric
gases
0°
LIFE ZONE
*
Freezing stops
all biochem rxns
INTERNAL COMPOSITION
Because of a generous portion of radioactive elements the Earth retains a liquid outer
core (within Earth’s interior) of iron and nickel that provides a mechanism for generating
a protective magnetic field that shields the surface from harmful solar radiation.
But…..
Remember, Theories Evolve…
NASA’s LCROSS mission in 2010
discovered “significant water on
the moon.”
•And, according to a paper just
published in Nature Geoscience,
Moon Water Differs from Earth
Water
•Moon rocks show that lunar water
has more heavy hydrogen than does
terrestrial water, indicating a
cometary origin.
•Could some of Earth’s water have “Houston, we have a problem”
originated from comet
bombardment?