Geobiology USC Astrobiology Searching for Life on Earth and Mars Carl Sagan Workshop July 17, 2019 Dr. Ken Nealson Dept. of Earth Science & Biological Sciences University of Southern California Geobiology USC Astrobiology TAKE HOME LESSONS FROM YESTERDAY: 1. Prokaryotes are chemists – small cells; high S/V; diverse chemistry; “no” predation Activities leave their catalytic signatures everywhere 1. Eukaryotes are Biologists – predator/prey; low S/V; ”simple” chemistry/ complex Behaviour 2. Early life was anoxic, prokaryotic, slow growing, non-motile, communal 3. Oxygen changed everything 4. Prokaryotic life leaves its fingerprints everywhere – we just need to recognize them! LiFe’s “Fingerprint” on the iron cycle: Corg-Fe – biosignature Siderophore-Fe(III) Oxygen Protection (SOD, peroxidases, etc.) Magnetotactic Bacteria -Fe3O4 Fe(II) Fe(OH)3 FeOB oxic PSAnFeOB anoxic AnFeOB After: Fe(II) Fe(OH) 3 Stumm & Morgan, 1996 FeRB Fe(OOH) Aquatic Chemistry Fe O 2 3 Wiley & Sons, Inc. FeSx,FeCO3,Fe3O4,Fe3S4, One can do this For every elemental cycle on Earth !! Geobiology USC Astrobiology TODAY: Strategy for life detection in samples from Earth or Mars Can we develop a non-Earth-centric (NEC) method for life detection (LD)? Comes from many discussions during my time at JPL -- MSR mission Many efforts to detect life in extreme environments on Earth Deep Subsurface – terrestrial & marine (dark, dry, low nutrients) Anaerobic caves – CO2/air interface (dark, dry, low nutrients) Permafrost – cold, low liquid water Acidic/hot springs – pH ~ 4, T ~ 90 C Serpentinization sites (pH ~ 12, Eh -600 mV) Geobiology USC Astrobiology Result of many discussions with members of the Astrobiology group at JPL during the time I was there. Sasha Tsapin Michael Storrie-Lombardi Gene McDonald Pan Conrad Rohit Bhartia Bill Hug Every Morning: Coffee and “can we develop a non-earthcentric method” Geobiology USC Astrobiology Why non-earthcentric ?? Does life have to be like earthly life? Why? Could we detect it if it was different? How ? Could we (you) devise a non-EC strategy? (How?) Which properties of life are universal? Which properties of life can be quantified ? Geobiology USC Astrobiology RULES OF THE “NON-EARTHCENTRIC” (NEC) ROAD !! Earth Centric = DNA, Fish Probes, Genomics RNA: transcriptomics Proteins: Proteomics, specific tests Lipids: biomarkers Stains: DNA,RNA,Membranes Non-Earth Centric = ?? Geobiology USC Astrobiology What are the things that life HAS or DOES ?? 1. Takes Energy from the environment (Thermodynamics) 2. Creates Waste products as it metabolizes 3. Should be able to alter rates of reactions (kinetics) 4. Some kind of complex and unique chemistry -- (composition) 5. Unique and complex chemistry – (function) 6. Reproduction (making copies) 7. Should be able to adapt and change over time (evolution) 8. Should be able to move – (non-random movement) 9. Will almost certainly alter the environment: atmospheric gases isotopic signatures of gases and solids: types and abundances of minerals Geobiology USC Astrobiology Fundamental Features of Life Many Copies (never see just one!) ENERGY CONSUMPTION REPLICATION LIFE SHAPE COMPOSITION -- Complexity -- PRODUCTS: WASTE BIOMINERALS EVOLUTION CELLS ACTIVITIES: Many Different Shapes MOVEMENT Metabolic Diversity (molecules, cells, etc.) Geobiology USC Astrobiology Characteristics of Living Systems Can we divine any Universal Features?: 1. Complexity of structure and function cells and cell components metabolism and rapid reactions 2. Non-equilibrium chemistry cell components and make-up storage materials 3. Observable environmental effects establishment of chemical gradients and layers 4. Non-random movement Geobiology USC Astrobiology Approaches to Life Detection Structure and Thermodynamics Non-Random Chemistry and Kinetics Movement A. Find the structures A. Define the system A. Observe Movement • Spatial scales B. Determine their • Energy sources • Temporal scales Chemistry • Electron donors • Electron acceptors • Data treatment • Elemental composition • Chiral composition B. Identify temporal • Isotope fractionation and spatial extents • Complex molecules of energy disequilibria • Layer formation • Temporal disruptions Geobiology USC Astrobiology What can we learn by studying the Earth, that will help us in the search for life on Mars? 1. Life is tough (extremophiles) 2. Life is tenacious (long survival times) 3. Life is metabolically diverse (it eats anything, it breathes anything !!) 4. When conditions get tough, life moves inside the rocks! 5. Life alters the rocks in ways that are recognizable Geobiology USC Astrobiology Life Detection Approach #1: Chemistry and Structure • Look for Complexity - Spatial Scales Search space - Temporal Scales must decrease • Look for Structures • Analyze Chemistry of Structures • Statistical Analyses (First find the Haystacks!!) (Look there for the Needles !!) Geobiology USC Astrobiology Antarctic Dry Valley Cryptoendolithic Community Visible Laser Induced Native Fluorescence (2a) 1.5X (2b) 1.5X (2c) 60X 0.5 mm 1.0 mm Center for Life Detection, JPL/CIT Deep UV Native Fluorescence Microscope – Photon Systems; JPL; USC effort Deep UV 224nm Laser Deep UV Sensitive- EMCCD (Photon Counting) High Transmission UV Emission filters Custom Deep UV Filter Block Deep UV Reflective objective lens Geobiology USC Astrobiology Native Fluorescence of Shewanella MR1 Compare to transmitted light methods Area of laser illumination Can this compete with standard microscopy? Phase contrast on a microscope slide – does pretty well (millisecond pulses) Geobiology USC Astrobiology Elemental Composition: Redfield ratio indicates that all earthly life is composed of roughly the same elements. C:N:P (100:15:1) Also contains HOKN Ca Fe Mg No mineral on the planet has this composition Far too much nitrogen, and all the other things make it unique Imagine that life on other planet would have same evolutionary trend – to be different from its environment !! Geobiology USC Astrobiology Components of Earth’s Crust and Life Earth% Life% Ratio (L/E) • Oxygen 50 50 ~ 1 • Silicon 26 – <.001 • Aluminum 7.5 – <.001 • Hydrogen 0.5 7 ~14 • Phosphorus 0.5 1 ~2 • Nitrogen 0.05 6 ~110 • Carbon 0.05 25 ~500 Comparisons 1 2 H He 1.01 Major 4.00 3 4 5 6 7 8 9 10 Li Be Trace B C N O F Ne 6.94 9.01 10.81 12.01 14.01 16.00 19.00 20.18 11 12 13 14 15 16 17 18 Na Mg Al Si P S Cl Ar 22.99 24.31 26.98 28.09 30.97 32.06 35.45 39.95 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 39.10 40.08 44.96 47.88 50.94 52.00 54.94 55.85 58.93 58.69 63.55 65.39 69.72 72.59 74.92 78.96 79.90 83.80 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 85.47 87.62 88.91 91.22 92.91 95.94 (98) 101.07 102.91 106.42 107.87 112.41 114.82 118.71 121.75 127.60 126.91 131.29 55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 Cs Ba La Hf Ta W Re Os Ir Pt Au Hq Tl Pb Bi Po At Rn 132.91 137.33 138.91 178.49 180.95 183.85 186.21 190.2 192.22 195.08 196.97 200.59 204.38 207.2 208.98 (209) (210) (222) 87 88 89 104 105 106 107 108 109 110 111 112 Fr Ra Ac Rf Ha Sg Ns Hs Mt Uun Uuu Uub (223) 226.03 227.03 (261) (262) (263) (262) (266) (266) (269) (272) (277) 58 59 60 61 62 63 64 65 66 67 68 69 70 71 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 140.12 140.91 144.24 (145) 150.36 151.96 157.25 158.93 162.50 164.93 167.26 168.93 173.04 174.97 90 91 92 93 94 95 96 97 98 99 100 101 102 103 Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 232.03 231.04 238.03 237.05 (244) (243) (247) (247) (251) (252) (257) (258) (259) (260) Geobiology USC Astrobiology Find the structures that look like life! (Ca,F) (Fe,O) (Mn, O) Elemental Analysis via Nano-SIMS (C,N,P,S,K,Ca (Sec. Ionization Mass spectrom.) Fe,Ni,Mn,etc) Composition and Distribution Composition: Thermodynamics predicts abundances Life gives a totally unpredicted distribution Examples: amino acids – number and amounts -- Easy chirality of amino acids Difficult sugars – number and amounts -- Easy chirality of sugars -- Difficult Lipids – fatty acid numbers and amounts -- Easy Proteins – totally unpredicted !! Data Base: all L, only 20 ! Geobiology USC Astrobiology Saturated monocarboxylic acids from abiotic sources, normalized to acetate A-881458 CM2 chondrite 10 Synthesis Murchison 1 0.1 0.01 0.001 Relative Molar ConcentrationRelative Molar 0.0001 2 3 4 5 6 7 8 9 10 11 12 Carbon Number Saturated monocarboxylic acids in sediments relative concentration normalized to 16:0 1 0.8 0.6 0.4 0.2 Relative molar concentration Relative molar 0 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 28 Carbon number Geobiology USC Astrobiology Life Detection Approach #2 • Look for activities - nutrient uptake - product excretion • Use thermodynamic logic • Measure kinetics - variety of temporal scales needed Geobiology USC Astrobiology Biogeochemical Processes Oxygen Diffusion from Atmosphere Oxygenic Photosynthesis Oxygen Respiration Nitrification Denitrification Mn oxidation Mn reduction Fe oxidation Fe reduction Sulfide oxidation Sulfate reduction Geobiology USC Astrobiology Occurrences of LMCs O2 - O2 NO3 Biofilms -- micrometers - Mn(IV) NO3 Fe(III) 2- Mn(IV) SO4 CO2 Fe(III) 2- SO4 Stratified Lakes CO2 And Marine Water Saturated Basins Sediments and Particles in Unsaturated Sediments (meters) Mat Systems (mm - micrometers) (cm – mms) Geobiology USC Astrobiology Geobiology USC Astrobiology To Summarize: Life leaves distinct kinetic signatures Prokaryotic life is responsible for most of these Expression of metabolic diversity Very strong imprint on the Earth Should be recognizable on any planet if life is there! Geobiology USC Astrobiology Article Design and preliminary verifications of an instrument to study the evolution of electrochemical gradients Radu Popa 1, Vily M.