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![Page 1: Astrobiology in the Context of a Research University Dimitar D. Sasselov Center for Planetary Astrophysics & Department of Astronomy Harvard University.](https://reader035.fdocuments.in/reader035/viewer/2022070308/551beb6c550346b9588b6311/html5/thumbnails/1.jpg)
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Astrobiology in the Context of a Research University
Dimitar D. Sasselov
Center for Planetary Astrophysics &Department of Astronomy Harvard University
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One of Humankind’s Biggest Questions:
What is the path from Stars to Life ?
• One of the last remaining unresolved questions
• It has become tractable by modern science• Major emerging discipline - one could lead !
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The “Essence” of Life
• Resolving the “Chicken-&-Egg” problem of nucleic acids vs. proteins - too much complexity ?
• Solution: RNA-catalyzed RNA replication !
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The “Essence” of Life
• Find how Darwinian behavior can emerge from chemistry
• Develop synthetic self-replicating molecules
• Membranes & vesicles - cell division before cells !
RNA (red) adsorbed into clay, inside a vesicle (green) - Szostak lab (2004).
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The Ultimate Leap: Chemistry to Life
• Prebiotic chemistry: find a plausible route to “self-replicators”;
• Prebiotic chemistry: on mineral surfaces, inside atmospheric particles, and ice-eutectic reactions;
• Prebiotic chemistry: on the young Earth, other planets and in space ?
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Co-evolution of Planets and Life
• Life as a planetary phenomenon:
constraining the chemical pathways that led to life.
• Unearthing the evidence - how did it all begun on Earth ?
• The next big question - was Mars alive ?
A fossil cyanobacteriumin circa 1.5 Gyr old sedimentary rocks - (A. Knoll).
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distinct layers of sedimentary rocks
(A. Knoll,Sept. 2004)
Mars,Endurance Crater
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The Universe is the “stage”…
• Planets - cradles for life in a hostile Universe
• Search & exploration: by end of decade - know planets like Earth
• Formation & stability of planetary systems
Artist concept of a hot Jupiter
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The Planetary Perspective
• The initial condition: chemical makeup & isotopes;
• Precise timeline of early events.
A pre-solar SiC grain from theMurchison meteorite.
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
2 microns
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The Planetary Perspective
• Precise timeline of early events.
Jacobsen (2003)
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Planets Orbiting Other Stars
Number of planets discovered around stars like our Sun:
154 planets 14 multiple planet systems
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Transits: A New Method for Planet Discovery
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Venus in Front of the Sun
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
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Transit Measurements
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Evidence for Planet OGLE-TR-56b
Light Dimming
Doppler Shift
Konacki, Torres, Jha,
Sasselov, 2003, Nature
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Mass-Radius diagram:
Kon
acki
, Tor
res,
Sas
selo
v, J
ha (
2005
)
All knowntransitingextra-solarplanets
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HD 209458b: a Hot Jupiter
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The Next Step:Find Planets like Earth
Lynnette Cook
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KEPLER: Search for Earth Twins
GOAL: discover ~12 Earths in habitable zones; also - thousands of giant planets like Jupiter.
NASA Mission - launch in 2007
Transit Search: ~100,000 stars
Can detect planets like our Earth
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Why in a University ?
• A major emerging discipline.
• Education: a bridge b/n life & physical sciences– Undergraduate: e.g. Harvard Melton/Gross committee– Graduate: specialized courses; workshops– Public outreach: immense potential (lecture series, etc)
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Special thanks to team members:
S. Jacobsen, J. Szostak, A. Knoll, S. Martin, M. Shair
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Additional Slides
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The Other Known Transiting Extrasolar Planet
HD 209458b: Dimming of light due to transit, observed with HST.
Brown, Charbonneau, Gilliland, Noyes, Burrows (2001)
Tells usDIRECTLY:Planet radius,
INDIRECTLY:Planet densityPlanet composition
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Model: Seager & Sasselov 2000
Detection: Charbonneau et al 2002
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NASA’s Terrestrial Planet Finder
• Find and characterize Earth-like planets
• Reduce the glare of the parent star by one million to one billion
• Launch date 2015
• Observe stars within 50 light years
Alcatel Space Industries
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At Harvard NOW:
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NEXT:
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The Ultimate Leap: Chemistry to Life
RNA (r