1 / 25

Early Earth and the Origins of Life Why do we care? How old do you think Life is?

Early Earth and the Origins of Life Why do we care? How old do you think Life is?. Early Earth and the Origins of Life August 26, 2011. Lecture overview : formation of the solar system and Earth conditions on early Earth theories concerning the origin of life on Earth

vachel
Download Presentation

Early Earth and the Origins of Life Why do we care? How old do you think Life is?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Early Earth and the Origins of Life Why do we care? How old do you think Life is?

  2. Early Earth and the Origins of Life August 26, 2011 • Lecture overview: • formation of the solar system and Earth • conditions on early Earth • theories concerning the origin of life on Earth • geologic evidence for earliest life on Earth

  3. The Geologic Timescale LIFE Life!?!

  4. Planetary disk with thanks to L. T. Elkins-Tanton, JPL NASA/JPL

  5. Ca-Al inclusions in carbonaceous chondrites: 4.5672±0.0006 Ga (billion years ago)

  6. Elkins-Tanton Linked solidification and cooling processes magma oceans at first…

  7. Formation of the Moon: 4.53Ga Moon forms from debris of a collision between a Mars-sized body and Earth Animation of moon formation, courtesy of Joe Tucciarone

  8. The Archean Earth System Archean: 4.03 to 2.5 Ga (Ga=billion years ago) • Late Heavy Bombardment (4.1 to 3.8 Ga) • Atmosphere: hardly any molecular oxygen (O2); appears at ~2Ga  earliest life probably anearobic! • UV radiation (no ozone shield)  earliest life probably underwater! • CO2 and CH4 -rich atmosphere • Likely warm surface conditions (80o to 45oC) • High rate of heat transfer from core to surface, possible thin crust, plate tectonics just being established w/ thanks to Stanley M. Awramik, UCSB

  9. Steps towards Life • synthesize biomolecules (organic C, amino acids) • organize them into macromolecular systems • emergence of self-replicating codes of molecules (RNA) • emergence of molecular evolution via natural selection after Hazen, 2006

  10. The Miller/Urey Experiment • Stanley Miller and Harold Urey (1953) • ran experiment for one week • observed 10% of C in organic form • 2% of C in amino acid form • but: • too high-energy environment • (lightning not continuous) • -early Earth contained appreciable • CO2 (in addition to CH4) • on the other hand… • -meteorites contain appreciable • amino acids

  11. A modern-day Miller/Urey experiment Jeff Bada, Scripps Inst. of Oceanography • redid the Miller/Urey experiment in 2007 • found 22 amino acids (more than M/U!) • also analyzed the original M/U vials • using modern-day analytical techniques Johnson et al., Science, 2008

  12. “Hot volcanoe” and “cold soup” models regarding the origin of Life on Earth -organic molecules and amino acids can be organized by mineral lattices as templates Hazen, 2006 What about combining the two? hydrothermal vents

  13. A schematic of evolution of life on Earth Modified from Awramik and McNamara, in press

  14. Stromatolites: biofilms of cyanobacteria capture and bind sediment Pre-Cambrian? Today, at Shark’s Bay, Australia

  15. An Opinion • “…true consensus for life’s existence seems to be reached only with the bacterial fossils of the 1.9-billion-year-old Gunflint Formation…” Moorbath, S., 2005. Nature, 434, p. 155): Tyler & Barghoorn, Science, 1954 .

  16. Candidates for Early Archean Fossils

  17. 3.85Ga rock apatite (Ca-PO4) grain in rock Nature, 1996 “carbonaceous” remnant material after apatite dissolved with acid And the controversy continues….

  18. A primer for Schopf et al., 2002 • ion microprobe • -instrument that focuses a beam of charged ions onto the surface of a sample • charged ions generate ions for mass spectrometric analysis (separation by mass) • in this case, used to look at different “isotopes” of carbon

  19. Carbon isotopes -C has two stable isotopes (12 protons, different # neutrons): 12C (99%) and 13C (1%) -for the most part, they behave identically -however, there is a slight difference in their “reactivity” (12C > 13C) -photosynthesis: 12C is preferentially incorporated into biological materials (low 13C values) cross-section of a leaf Mojzsis, 1996

  20. Raman spectroscopy -instrument detects extremely small changes in energy of light/laser/IR radiation -in Schopf 2002, a laser is used to excite the sample molecules into a higher energy state; they report “Raman shifts” that denote changes in laser wavelength -shifts denote presence of specific chemical bonds and their relative orientations

  21. kerogen -concentrated, high-molecular-weight organic compounds occuring in sedimentary rocks -precursor to fossil fuels (formed upon heating of kerogen) an oil shale carbonate (containing CO3) -most commonly CaCO3, the mineral in limestone -many marine organisms form carbonate shells (corals, foraminifera) limestone cliffs

  22. trichome -any small outgrowth or appendage on certain plants and algae trichomes on a cannabis plant chert -finely-grained, silica-rich, microcrystalline rock -is a product of high-T chemical alteration of rocks

  23. greenschist -metamorphic rocks resulting from low-T, moderate pressure environments -typically somewhat green in color

More Related