Transcript Ddddddd

ASTR/GEOL-2040: Search for life
in the Universe, Lecture 1
What happened since 1976?
• Public lost interest after Viking 1 & 2 returned negative results
• NASA funded Astrobiology Institute in 1998 (also ALH84001)
• New insights & paradigm shifts in just the last 10-20 yr
2
The 4 cornerstones of astrobiology
>2001
4.6Gyr
>1996
Proxima Cen (red dot)
>2003
Exoplanets since 1995
3
 10 in habitable zone
Syllabus
• Weeks 1-4: Origin of life studies
– Bottom up (chemistry)
– Top down (biology)
• Weeks 5-7: Origin on Earth
– Habitable zones (astronomy)
– Geol. record (geology), extremoph (bio)
• Weeks 8-12: Mars, Europa, etc
– Planetology, geology, chemistry
• Weeks 13+14: exoplanets, SETI
4
Books
5
Grading
• 6 homeworks, best 5 will be graded
• Midterm exam , 2 quizzes
• In-class engagement, clicker grades
6
General remarks
• Office hours in 240D
• Tue+Thu 4:45-6:00, time OK?
A. Yes
B. Yes, but barely so
C. No, not at all
• This week: let me know about special
accommodations etc (email or talk to me)
– Notetaker (Kaitlin E): for the 3 w/ accomm.
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Alternative office hours
• For those where TTH 4:45 does not
work, which of the following works
A.
B.
C.
D.
E.
Mondays 12-1
Wednesdays 9-10:30
Wednesdays 10:30-12
Fridays 1-2
None of the above
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syllabus2
9
syllabus3
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Other remarks
• Teaching assistant:
– Daniel Everding
• Broad background in class
– astro, engl, anthrop, marketing, busin,
chem&bio eng, archit, aerosp, ling, phil,
phys, geol, evol bio, psych, hist, journ, …
• Cell-phones/laptop use distracts others
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About myself
• Why I’m here as 3-yr visiting professor
•
•
•
•
Why I’m interested in Space & the Sun
What else I did
…..
Sorry, what did you just say?
Sept 16, 1975
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14
15
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…then, what did I do?
Where
Age
New things
School
7-19
Age 14-16 rockets, electronics, 14-18 astronomy
Alternate service
19-21
astrophotography
Hamburg University
21-27
Convection, linear theory, interest in aurora
Helsinki University
27-31
PhD, magnetic fields, 3-D simulations
Nordita in Copenhagen
31-33
Accretion discs, supervised student
Newton Institute Camb.
33
In-depth exposure to many scientists
NCAR, Boulder, Colorado 33-35
Galactic magnetic fields, turbulence
Nordita, (assistant prof)
35-37
Early Universe, organized school, …
Newcastle (professor)
37-41
Teaching courses, project + PhD students
Nordita (professor)
41-47
Astrobiology, Pencil Code
Nordita (Stockholm)
47-56
Big European grant, own group, visitors
CU Boulder (vis faculty)
56-59
Solar physics, more astrobio, meteorology
Astrobiology nowadays
• microbial life should exist elsewhere
– we just have to find examples
– it could be in unimaginable places
• independent genesis  deeper
understanding about ourselves
• exobiology  astrobiology
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Science fiction  science hypothesis
• xx
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1865
1951
2000
Transition to life spontaneous?
• Prior to Louis Pasteur (1822-1895)
– Flies & maggots from rotting meat
– Lice from sweat
– Eels & fish from sea mud…
• Disproven by Pasteur
– All life from existing life
– First life: from non-living matter?
• Need a strategy
RGS p.2, Lon p.157, BS p.154+164-165
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What is life?
Life elsewhere might be different
Need to look for general properties
• Example: cat versus car
– get energy, can move, produce waste
– what’s different?
• Reproduces itself
RGS p.2, Lon p.157, BS p.154+164-165
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Properties of life?
1.
2.
3.
4.
5.
6.
…
….
…..
……
……..
……….
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Properties of life?
1.
2.
3.
4.
5.
6.
Order
Reproduction
Growth & development
Energy utilization
Response to environment
Evolutionary adaptation
RGS p.2, Lon p.157, BS p.154+164-165
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Thermodynamically ok?
• 1st law of TD: energy is conserved
– can be transferred between different
reservoirs (thermal, kinetic, chemical)
• 2nd law of TD: each time energy is
transferred, disorder of Universe incr.
 Life creates order & messes up surroundings
Lon p.161-163, BS p.157
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Darwinian evolution
•
•
•
•
More individuals produced than survive
Struggle for existence (limited resources)
Individuals show variation (often subtle)
Individuals produce similar offspring
Works also/especially at the molecular level:
RNA can replicate itself  RNA world
RGS p.2, Lon p.168, BS p.164,181
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Natural selection is
A. the occasional mutations that occur in DNA;
B. the mechanism by which advantageous traits are
preferentially passed on from parents to offspring;
C. the idea that organisms can develop new
characteristics during their lives and then pass
these on to their offspring.
BS p.195
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Natural selection is
A. the occasional mutations that occur in DNA;
B. the mechanism by which advantageous traits are
preferentially passed on from parents to offspring;
C. the idea that organisms can develop new
characteristics during their lives and then pass
these on to their offspring.
BS p.182
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Again: What is life?
automatically implies
input of matter & energy
• Replicate &
• Evolve through natural selection
Still unclear how life got started
Chemical vs biological evolution
Where exactly is the threshold?
Any definition may be challenged
as we have new observations
RGS p.2, BS p.164-165
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Which of the following is
not a key property of life?
A. The maintenance of order in
living cells
B. The ability to evolve over time
C. The ability to violate the second
law of thermodynamics?
RGS p.3, Lon p.171, BS p.166-167
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Which of the following is
not a key property of life?
A. The maintenance of order in
living cells
B. The ability to evolve over time
C. The ability to violate the second
law of thermodynamics?
RGS p.3, Lon p.171, BS p.166-167
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Why carbon
• Versatile, because it can bond with
a large range of different atoms
• Carbon compounds can readily
dissolve in water
RGS p.3, BS p.164-165
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Why not silicon?
• Si is larger, so bonds are weaker
• Si does not form double or triple
bonds as easily
• SiO2 is solid, not mobile like CO2
• In Earth’s crust, Si is 1000x more
abundant than C, but C won
RGS p.3, Lon p.171, BS p.166-167
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How is your chemistry?
What is ammonia?
A.
B.
C.
D.
E.
N2O
HCN
NH4Cl
NH3
HCOOH
RGS p.3, Lon p.171, BS p.166-167
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How is your chemistry?
A.
B.
C.
D.
E.
N2O
HCN
NH4Cl
NH3
HCOOH
 nitrous oxide
 hydrogen cyanide
 ammonium chloride
 ammonia
 formic acid
RGS p.3, Lon p.171, BS p.166-167
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Why water?
• To dissolve & transport organic
molecules,  available for reactions
• Is liquid over wide T range
• Alternatives; lower T, reactions slow
RGS p.4, Lon p.171-173, BS p.246-248
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Other reasons
• Ice floats & insulates deeper layers
• Water is a highly polar molecule
 hydrogen bonds (very stable)
• Dissolves other polar molecules
– Like dissolves like
• Does not dissolve apolar molecules
 critical for existence of cells
RGS p.5, Lon p.172-173, BS p.248
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What we talked about
• Definition of life
– Darwinian evolution, natural selection
– & self-replication
• Carbon, not silicon-based
• Water, a polar molecule, allows cells
made of lipids
• Next time: building blocks of life
– pp. 8-12, Sect. 1.2.4
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