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Life in the Universe

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Life in the Universe Northeastern Illinois University Life in the Universe Greg Anderson Department of Physics & Astronomy Northeastern Illinois University Winter-Spring 2020 c 2012-2020 G. Anderson Introduction to Astronomy – slide 1 / 92 Northeastern Illinois Overview University Daing Rocks Life on Earth How Did Life Arise? Life in the Solar System Life Around Other Stars Interstellar Travel SETI Review c 2012-2020 G. Anderson Introduction to Astronomy – slide 2 / 92 Northeastern Illinois University Daing Rocks Zircon Dating Sedimentary Grand Canyon Life on Earth How Did Life Arise? Life in the Solar System Life Around Daing Rocks Other Stars Interstellar Travel SETI Review c 2012-2020 G. Anderson Introduction to Astronomy – slide 3 / 92 Northeastern Illinois Zircon Dating University Zircon, (ZrSiO4), minerals incorporate trace amounts of uranium but reject lead. Naturally occuring uranium: • U-238: 99.27% • U-235: 0.72% Decay chains: • 238U −→ 206Pb, τ =4.47 Gyrs. • 235U −→ 207Pb, τ = 704 Myrs. 1956, Clair Camron Patterson dated the Canyon Diablo meteorite: τ =4.55 Gyrs. c 2012-2020 G. Anderson Introduction to Astronomy – slide 4 / 92 Northeastern Illinois Dating Sedimentary Rocks University • Relative ages: Deeper layers were deposited earlier • Absolute ages: Decay of radioactive isotopes old (deposited last) oldest (depositedolder first) c 2012-2020 G. Anderson Introduction to Astronomy – slide 5 / 92 Grand Canyon: Earth History from 200 million - 2 billion yrs ago. Northeastern Illinois University Daing Rocks Life on Earth Earth History Timeline Late Heavy Bombardment Hadean Greenland Shark Bay Stromatolites Cyanobacteria Life on Earth Q: Earliest Fossils? O2 History Q: Life on Earth How Did Life Arise? Life in the Solar System Life Around Other Stars Interstellar Travel SETI Review c 2012-2020 G. Anderson Introduction to Astronomy – slide 7 / 92 Northeastern Illinois Earth History University Earth Forms (4.6 Ga) Oxygen in Atmosphere Impact Forms Moon (4.5 Ga) Late Heavy Bombardment Isotopic Evidence (3.8 Ga) Stromatolites (3.45 Ga) Hadean Archean Proterozoic Phanerozoic 5 4 3 2 1 0 Billions of years ago c 2012-2020 G. Anderson Introduction to Astronomy – slide 8 / 92 Northeastern Illinois Earth History University Earth Forms (4.6 Ga) Oxygen in Atmosphere Impact Forms Moon (4.5 Ga) Late Heavy Bombardment Isotopic Evidence (3.8 Ga) Stromatolites (3.45 Ga) Hadean Archean Proterozoic Phanerozoic 5 4 3 2 1 0 Billions of years ago Paleozoic Mesozoic Cenozoic c OSD C P TR J K Pg N 550 450 350 250 150 50 Millions of years ago c 2012-2020 G. Anderson Introduction to Astronomy – slide 8 / 92 Northeastern Illinois Timeline for Early Life on Earth University Life arose on Earth soon after the end of late heavy bombardment. • 4.6 billion years ago (Ga) - earth forms • 4.2, 4.4 Ga - evidence of oceans (detrital zircon) • 4.1–3.8 (3.85-3.82) Ga – late heavy bombardment • 3.8 Ga – Isotopic % BIF evidence from Greenland • 3.5, 2.7 Ga – Stromatolites and other fossils. • 2.3 Ga – The great oxygenation event • 2.0 Ga – Evolution of Cells with Nuclei (Eukaryotes) • 1.2 Ga – Evolution of complex multicellular organisms • 0.5 Ga – Cambrian explosion c 2012-2020 G. Anderson Introduction to Astronomy – slide 9 / 92 Hadean Earth c Don Dixon Northeastern Illinois Evidence from Greenland (Controversial) University Greenland is home to some of the oldest rocks on Earth. • Oldest sedimentary rock at Isua 3.82 Ga • Banded iron formations (BIF), t> 3.7Ga at Isua may suggest life. • 13C depleted graphite found in the Isua schists, similar claims for Akilia 150 km to the SW. c 2012-2020 G. Anderson Introduction to Astronomy – slide 12 / 92 Fossil Stromatolites Modern stromatolites: Shark’s Bay Northeastern Illinois Cyanobacteria “blue-green algae” University • The fossil record for early life (Stromatolites) goes back 3.5 Gyrs (disputed) [2.7 Gyrs (undisputed). • Early photosynthesis created a great oxygenation event 2.4 Gyrs ago. • Cyanobacteria obtain their energy through photosynthesis, and pro- duce oxygen as a byproduct. • By releasing oxygen into the atmo- sphere, Cyanobacteria allowed for the evolution of more complex life- forms on Earth. c 2012-2020 G. Anderson Introduction to Astronomy – slide 14 / 92 Northeastern Illinois Q: Earliest Fossils? University According to fossil evidence, how far back in time did life on Earth exist? A) About 65 million years B) About 545 million years C) About 1.0 billion years D) > 2.7–3.5 billion years or more c 2012-2020 G. Anderson Introduction to Astronomy – slide 15 / 92 Northeastern Illinois Q: Earliest Fossils? University According to fossil evidence, how far back in time did life on Earth exist? A) About 65 million years B) About 545 million years C) About 1.0 billion years D) > 2.7–3.5 billion years or more Fossil stromatolites in Australia are 3.5 Ga. c 2012-2020 G. Anderson Introduction to Astronomy – slide 15 / 92 Northeastern Illinois History of Atmospheric Oxygen University • Before 2.3 Ga levels of atmospheric oxygen were to low to sustain aerobic life. • By 0.5–0.6 Ga, atmospheric oxygen was plentiful enough to support complex multicellular life. c 2012-2020 G. Anderson Introduction to Astronomy – slide 16 / 92 Northeastern Illinois Q: Life on Earth University You have a time machine with a dial that you can spin to send you randomly to any time in Earth’s history. If you spin the dial, travel through time, and walk out, what is most likely to happen to you? A) You’ll be eaten by dinosaurs. B) You’ll suffocate because you’ll be unable to breathe the air. C) You’ll be consumed by toxic bacteria. D) Nothing: you’ll probably be just fine. c 2012-2020 G. Anderson Introduction to Astronomy – slide 17 / 92 Northeastern Illinois Q: Life on Earth University You have a time machine with a dial that you can spin to send you randomly to any time in Earth’s history. If you spin the dial, travel through time, and walk out, what is most likely to happen to you? A) You’ll be eaten by dinosaurs. B) You’ll suffocate because you’ll be unable to breathe the air. C) You’ll be consumed by toxic bacteria. D) Nothing: you’ll probably be just fine. c 2012-2020 G. Anderson Introduction to Astronomy – slide 17 / 92 Northeastern Illinois University Daing Rocks Life on Earth How Did Life Arise? Origin of Life on Earth Phylogenetic tree Hydrothermal Vents How did life arise? Miller-Urey How Did Life Arise? Experiment (1953) RNA World Hypothesis pre-cells DNA DNA Strand Evolution Natural Selection Peppered Moth Q: Natural Selection? Life in the Solar System Life Around Other Stars Interstellar Travel c 2012-2020 G. Anderson Introduction to Astronomy – slide 18 / 92 Northeastern Illinois Origin of Life on Earth University Last Universal Common Ancestor (LUCA): • All life on Earth shares a common ancestry. • We may never know exactly how the first organism arose, but laboratory experiments suggest plausible scenarios. Possibilities include: • tidepools • hotsprings • deep sea hydrothermal vents c 2012-2020 G. Anderson Introduction to Astronomy – slide 19 / 92 Northeastern Illinois Hydrothermal Vents University Some lines of evidence, including DNA sequencing, suggest the first life earth may have been an extremophile which lived in extremely high temperatures near deep sea hydrothermal vents. c 2012-2020 G. Anderson Introduction to Astronomy – slide 21 / 92 Northeastern Illinois How did life arise? University 1. Simple organic molecules form 2. Replicating molecules (RNA?) evolve and begin to undergo natural selection. 3. Replicating molecules become enclosed within cell membranes. 4. Some cells evolve modern metabolic processes. 5. Multicellular life evolves c 2012-2020 G. Anderson Introduction to Astronomy – slide 22 / 92 Northeastern Illinois Miller-Urey Experiment (1953) University Stanley Miller & Harold Urey’s U. Chicago experiment to simulate conditions on early Earth: Ingredients for Primor- dial Soup: • Water (H2O) • Methane (CH4) • Ammonia (NH3) • Hydrogen (H2) Shocked, heated cooled, ...produced Amino acids: the building blocks for protiens. Modern versions of this experiment have produced even more builing blocks for life. c 2012-2020 G. Anderson Introduction to Astronomy – slide 23 / 92 Northeastern Illinois RNA World Hypothesis University The first life on earth used RNA to store genetic information and to catalyze chemical reactions. • Discovery of Ribozymes - RNA can catalyze chemical reactions. • Formation of long RNA strands may catalyzed by clays, salty ice water c 2012-2020 G. Anderson Introduction to Astronomy – slide 24 / 92 Northeastern Illinois pre-cells University Clay minerals catalyze formation of membranes around RNA. c 2012-2020 G. Anderson Introduction to Astronomy – slide 25 / 92 Northeastern Illinois Deoxyribonucleic acid (DNA) University Molecule that encodes the genetic instructions for all living cells. Double helix composed of the nucleotides. Nu- cleotide = nucleobase + deoxyribose sugar + phosphate group. Nucleobases: • Guanine (G): C5H5N5O • Adenine (A): C5H5N5 • Thymine (T): C5H6N2O2 • Cytosine (C): C4H5N3O c 2012-2020 G. Anderson Introduction to Astronomy – slide 26 / 92 Northeastern Illinois Evolution University Evolution: The change in the inherited characteristics of biological populations over successive generations. • All life on earth has decended a common ancestor. • The fossil record shows evolution has occurred through time. • Darwin’s theory of natural selection tells us how this evolution occurs. • This theory was supported by the discovery of DNA: our genetic information is stored in DNA, evolution proceeds through mutations. c 2012-2020 G. Anderson Introduction to Astronomy – slide 28 / 92 Northeastern Illinois Natural Selection University Charles Darwin (1809–1882), The Origin of Species (1859). Natural Selection: • Variations exists within all populations of organisms. • More offspring are produced than can possibly survive. • Individuals with certain traits are more likely to reproduce. • Over time the population evolves. c 2012-2020 G. Anderson Introduction to Astronomy – slide 29 / 92 Northeastern Illinois Evolution of the Peppered Moth University Peppered Moth (Biston betularia): Studied for 200 years.
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