PTYS 214 Spring Announcements

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Edwin Butler
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1 PTYS 214 Spring 2018 Announcements Midterm #2 next Thursday (2/8)!!! Woah!!! Lunar eclipse tomorrow morning! - Begin: 3:51 am - Max: 6:30 am - Sets: 7:15 am - End: 9:08 am Observing project (may replace final exam) - Photograph the moon throughout its orbit - Write an essay relating your observations to astrobiology - Same due dates as writing assignment: 4/17 / 4/26; 2 pm!

2 Steward Observatory 21 Telescope Telescope Sign-up sheet SS308

3 Last Time DNA, RNA Replication Transcription Translation Cells Prokaryotes Eukaryotes Earliest biology -- top-down approach RNA world Metabolism first

Bottom-Up Approach: Primordial Soup Theory Life began in a warm pond/ocean from a combination of basic building blocks of life (organic molecules)

4 Bottom-Up Approach: Primordial Soup Theory Life began in a warm pond/ocean from a combination of basic building blocks of life (organic molecules) into ever more complex organic molecules, such as amino acids, proteins, and some early version of RNA Where did the building blocks of life come from?

photosynthesis): CO2 + H2O CH2O + O2 (CH2O any organic matter) CO2 gas mixture does not

5 Building Blocks of Life: Atmosphere Carbon that comes out of volcanoes is in the form of CO 2 Almost all organic carbon that we observe today is produced biologically (via photosynthesis): CO2 + H2O CH2O + O2 (CH2O any organic matter) CO2 gas mixture does not produce organic molecules on its own Where did organics come from before there was life? organic inorganic

6 Ancient atmosphere Urey-Miller Experiment CH4 NH3 H2O C HCN (cyanide) H H2CO (fomaldehyde) N O Spark discharge breaks the chemical bonds in CH4, NH3, H2O Amino acids Other simple organics C, H, N, O atoms can recombine into various organic molecules that eventually end up in the ocean

7 Problems of organic synthesis via Urey-Miller experiment Debate over the presence of large amounts of NH3 and CH4 in the early (pre-biotic) atmosphere In a CO2-rich atmosphere organic production by spark discharge is not very efficient If CH4/CO2 < 0.1 essentially no organic production

8 CO2-Dominated Atmosphere In an atmosphere dominated by CO2 the most abundant radical after spark discharge or photolysis is O CO2 >> CH4, NH3 O >> C,N,H CO NO NO2 H2O The dominant species after recombination are inorganic molecules! Current Research: organic production in CO2-N2-H2 mixtures

9 Organic synthesis in Hydrothermal Vents Dr. Sven Peterson IFM-GEOPMAR, Keil 9

mid-ocean ridges Old material is subducted back into the mantle at continental margins

10 Plate tectonics: Mid-ocean ridges Mantle circulation produces stresses on the Earth s crust Spreading centers form on the ocean floor, where the crust is thinnest -- mid-ocean ridges Old material is subducted back into the mantle at continental margins Mid-ocean ridges combine water, high temperatures, silicate minerals - hydrothermal vents 10

11 Organic synthesis in Hydrothermal Vents Hydrothermal vents were likely to be present in the pre-biotic environment Organic synthesis requires only CO2, H2O and silicate rocks (and heat!) Example: Serpentinization: Olivine + Seawater & dissolved CO2 Spinel polymerization: Methane Serpentine Ethane Hematite + Magnetite (spinel group)

12 Organic synthesis in Hydrothermal Vents Actually, the story may be more complicated: McDermott et al., PNAS 112; May 2015 Some organics formed through processes other than serpentinization

13 Both atmosphere and hydrothermal vents have problems producing complex organics Can you think of any other source of organic matter?

14 Both atmosphere and hydrothermal vents have problems producing complex organics Can you think of any other source of organic matter? Space! Extraterrestrial origin organic material was synthesized in space and was brought to Earth somehow

15 ~150 interstellar and circumstellar molecules H2 CH4 NH3 C6H6 Glycine

16 Giant molecular cloud Star/planet formation

17 Do we have examples of extraterrestrial material on Earth?

18 Do we have examples of extraterrestrial material on Earth? Meteorites! Murchison (1969, Australia)

Meteorites Natural objects originating in outer space that survive an impact with the Earth's surface without being destroyed Achondrites 8%

19 Meteorites Natural objects originating in outer space that survive an impact with the Earth's surface without being destroyed Achondrites 8% Irons/Stony irons 6% Chondrites 86% (oldest rocks in the solar system) 5% are Carbonaceous Chondrites: - amino acids - hydrocarbons - fullerenes - etc..

20 Some of the amino acids synthesized in the Miller-Urey experiment and also found in the Murchison meteorite

21 Comet 67P/ChuryumovGerasimenko Target of ESA's Rosetta/Philae mission Philae lander found 16 organic compounds 4 had never been seen before in comets Goesmann et al. Science 349; July 2015

22 Problems with Extraterrestrial Organic Delivery Simple organics only no large macromolecules It is hard to accumulate necessary mass of carbon for the concentrated pre-biotic soup (dilution problem)

23 The Phosphorus Problem Cosmic H O 1400 C 680 N 230 S 43 P 1 Phosphorus is a very rare element in the universe On Earth it is found as insoluble phosphate minerals

24 Why do we care about phosphorus? (Come back zinc!)

25 Without Phosphorous there would be no: ATP... Nucleic acids (DNA,RNA) or Phospholipids Come back Phosphorus!

26 Extraterrestrial P Two forms: Phosphate Ca5(PO4)3(OH,F) like typical phosphates on Earth Schreibersite (Fe,Ni)3P NOT a naturallyoccurring crustal mineral Seymchan meteorite (pallasite) 20 cm

Phosphorus on the Earth s surface Phosphates are not soluble in water at normal terrestrial conditions Schreibersite rusts in presence of water to form soluble

27 Phosphorus on the Earth s surface Phosphates are not soluble in water at normal terrestrial conditions Schreibersite rusts in presence of water to form soluble and reactive P Meteorites may be an important source of P for the origin of life Pasek (2008) Rethinking early Earth phosphorus geochemistry PNAS 105(3), p.853

have come from three sources in the pre-biotic world: Synthesis

28 Bottom-Up Approach - Synopsis 1. Small organic molecules Small organic carbon molecules could have come from three sources in the pre-biotic world: Synthesis in the atmosphere Synthesis in the hydrothermal vents Synthesis in space and delivery via meteorites

29 Bottom-Up Approach - Synopsis 2. Subunits of RNA Phosphates: rock (meteorite) weathering Ribose: 5 CH2O + H2O C5H10O5 (formaldehyde from U-M) Bases: 5 HCN + NH3 Adenine (hydrogen cyanide from U-M) (and similar reactions for the other 3 RNA bases)

30 Bottom-Up Approach - Synopsis 3. Polymerization Formation of longer molecules from simple organic molecules Dehydration reaction: two simpler organic molecules are bonded through the loss of water H2O

template for polymerization Small organic molecules

31 Minerals can help polymerization Minerals (like clay and pyrite) can provide a repeating pattern to act as a template for polymerization Small organic molecules could have stuck to the mineral surface (organic film) Kaolinite

32 The Dilution Problem Primordial soup was probably too dilute in simple monomers to form very long molecules Possible concentration mechanisms: Tidal pools (evaporation) Freezing water Mineral catalysts (clays) All of them are quite inefficient compared to enzymes and cells

33 Bottom-Up Approach - Synopsis 4. Formation of the cell membrane = water-loving Lipids have hydrophilic head and hydrophobic tail In solution these lipids can form monolayers, bilayers and bilayer vesicles spontaneously proto-cells

34 Monolayer Bilayer Bilayer vesicle Micelles Cell Membrane

35 Bottom-Up Approach: Summary 1. There are 3 sources of small organic carbon molecules (up to amino acids, sugars) in the pre-biotic world 2. Small organic molecules must combine to form the basic sub-units of RNA 3. Polymerization allows for the formation of organic macromolecules Dilution Problem The primordial soup was probably too dilute in simple monomers to form very long molecules (a concentration mechanism is required) 35

36 The RNA-first World Short strands of RNA-like molecules were produced spontaneously (with some help, e.g. minerals) Eventually some of the RNA-like molecules were able to catalyze their own replication A G G C U U C C G A G G C U U C C G A Copying errors introduced mutations and therefore Darwinian-like evolution 36

37 First DNA-based Life Through natural selection life figured out that: DNA is a better way to store the hereditary information: more stable (better protected) Fewer replication errors Less susceptible to certain mutations Proteins are more efficient catalysts than RNA 37

38 Central problem for the origin of life: Simple organic molecules RNA world Metabolism first? Replication first? + Dilution problem 38

39 Origin of Life on EARTH: Summary Bada & Lazcano (Science, 2002) 39

40 Homework Homework #5 available shortly on the web site

Astrobiology. Joseph Spitale

Astrobiology. Joseph Spitale Astrobiology Joseph Spitale 1 What is Astrobiology? Science that studies the origin, evolution, distribution, and future of life in the universe - Combines many sciences: Biology, Chemistry, Planetary