Kiwa hirsuta “ye$ crab? Size: Carapace length, 51.5 mm, total length 88.4 mm Distribu,on : Pacific Antarc$c Rise – German Flats, 38S Biology: Occurs at densi$es of one or two individuals per 10 meters, more or less regularly spaced on the zone of pillow basalts surrounding ac$ve hydrothermal vents, and at the base of chimneys among vent mussles ( Bathymodiolus sp ) other crabs and ophidiid fish. Omnivorous.
Ye, Crab
41 st Saas‐Fee course from Planets to Life 3‐9 April 2011 Lecture 6 ‐ Origin of Life and its Early Evolu$on on Earth • Mineral needs – con$nued • Condi$ons on Earth that provide the essen$als for life to start and evolve – Tectonics, chemical energy sources, trace elements, minerals • Metabolism and geochemistry – Early metabolism – The Earth’s “enrichment period” • The first microbial community – a possible model system
How to get high concentra$ons of useful organic compounds? • Specific synthesis – requires catalysts (minerals) • Very limited data at the present $me, but preliminary data looks very promising Keep in mind that the cataly$c reac$ons carried out by proteins in present‐day organisms was very likely carried out by minerals before the gene$c code and ribosomes were fully developed Some early ideas about minerals and the origin of life
Cairns‐Smith Clay Model for the origin of life Clay crystals Crystal growth and “muta$on” Informa$on stored in crystals as a Condense organic compounds group of crystal “defects” that can be replicated through cleavage (clays as templates and and crystal growth reac$ve surfaces)“organic takeover” Macromolecules Crystal growth occurs by addi$on of units of the kink edge of a con$nuous ramp Cells spiraling around the central core
Organic reac,on on pyrite surfaces under hydrothermal condi,ons (Wächterhäuser, 1988, 1998) Pyrite Examples of possible reac,ons involving pyrite based on pyrite having a ca,onic surface in which a variety of anionic reac,ons are possible. The example in (A) is the adsorp,on of glyceraldehyde‐3‐phoshate to the surface followed by polymeriza,on. (B) Par,cipa,on of pyrite in a reac,on that can drive and otherwise energe,cally unfavorable reac,on. For example, the reduc,on of CO 2 by H 2 has a posi,ve Gibbs free energy reac,on. However, if CO 2 reduc,on is linked to the pyrite reac,on the synthesis of formic acid is energe,cally favorable
Models for the origin of life in Russell Model 1990’s vent environments Wächterhäuser Model 1980’s FeS membranes (bubbles formed from a mix of acidic seawater and alkaline hydrothermal fluid) Pyrite Organic synthesis ( Δ Eh across membrane) Organic synthesis and condensa$on Metabolic pathway “surface metabolites” Condensa$on reac$ons Informa$on Informa$on macromolecules Macromolecules CELLS CELLS
Some ongoing work with minerals References of interest: 1. Hazen, R.M. et al., 2008. Mineral evolu$on. American Mineralogist 93:1693‐1720 2. Cody, G. J. 2004. Transi$on metal sulfides and the origin of metabolism. Ann. Rev. Earth Planet. Sci. 32:569‐599
Mineral surfaces that may be involved in the origin of life Elemental composi$on Mineral Surface Properties Lava minerals Si, O, Fe Major mineral surface on early Earth 2- Apatite Ca, PO 4 Primary phosphate mineral Clays Si, Al, O Can organize organics into films and catalyze polymerization reactions Pyrite FeS 2 Source of reducing power Calcite CaCO 3 Chiral surfaces; concentrate organics such nucleotides from models Quartz SiO 2 Chiral surfaces Ultramafic minerals Fe, Mg Generate hydrogen and organic compounds from CO 2 Borate minerals B Catalyze the synthesis of ribose
Mineral Needs • Catalyze metabolic networks that involve the reduc$on of CO 2 to organic compounds. • There is a need to iden$fy the cataly$c ability of other minerals under different T/ pH condi$ons (minerals that mimic known enzyme groups: oxidoreductases, transferases, hydrolases, lyases, isomerases and ligases) We can accomplish this by looking at minerals that contain the metals that are present in different minerals and examine their cataly,c ac,vity under the environmental condi,ons that they can form and remain stable
Are there realis$c early‐Earth segngs that support the “metabolism first”, or the “replicator first” and the encapsula$on models? What about the source sites of cataly$c minerals? • The answer is there is much we don’t know
Condi$ons on Earth that provide the essen$als for life to start and evolve – Some hypotheses • Earth‐like planets (acBve tectonism ) will support life that uses both chemical and light energy: the “Unity of Metabolism.” • Prior to the appearance of heterotrophic eukaryotes (single celled pro8sts), Earth’s microbial ecosystems would have been characterized by extremely high densi$es of specific metabolic groups of microbes: “The Enrichment Period” (the red, purple or green planet). • The enrichment periods have the poten$al to affect the chemistry of the atmosphere.
Why is tectonism important for life? • Water present • Generate new crust and con$nents • Produce hydrothermal systems – Source of carbon, chemical energy and elements required for life (magma degassing, water/rock reac$ons and mineral catalysis) – Possible segng for the earliest microbial ecosystems – A possible “required” segng for the origin of life or steps leading to life
The “Unity of Metabolism” predicts that organisms (even with different biochemistries than Earth organisms) on any tectonically ac$ve planet (water) will use the same chemical energy sources and electron acceptors and donors as Earth organisms
Vola$les from magma‐hosted and perido$te‐hosted vents ‐ could they be detected in the atmosphere? • Vola$les from Magma‐hosted vents: 3 He, H 2 , CH 4 , CO 2 , H 2 S, CO • Vola$les from perido$te‐hosted vents: 3 He, H 2 , CH 4 , C 1 ‐C 5 hydrocarbons • Modeling the atmosphere of a tectonically ac,ve planet without life and with ecosystems at various stages in Earth’s history
Different microbial ecosystems/different atmospheres (chemical composi$on ) • Earth without oxygen and eukaryotes (the absence of animal predators) • The “Enrichment Period” of Earth history • A pale dot of different hues
Noachian Hesperian Amazonian atmospheric loss 5.0 4.0 3.0 2.0 1.0 0.0 Billions of years on Mars Late heavy bombardment Solar system forma$on Archaean Proterozoic Phanerozoic Archaean s e s d t o n pO 2 <0.002 bar pO 2 >0.03 bar pO 2 >0.2 bar s P O 2 <0.002 bar e i p v e e n n o o $ $ a a Ferrous ocean ferrous oceans sulfidic ocean oxic ocean n n e e g g Anoxygenic y y x x o o Photosynthesis, / / g g cyanobacteria algae, pro$sts complex n n Cyanobacteria i i z z e (2.7 Ga) e animals & (2.7 Ga) e e r r f f plants e y microbes t l Microbes r a a L E 5.0 4.0 3.0 2.0 1.0 0.0 Billions of years ago on Earth
10 33 Impact energy (J ) 10 31 Water evaporated (m) 10 29 3000 10 27 30 10 25 0.3 0.003 10 23 origin of life K/T 10 21 Ty 4 3 2 1 0 Time (Ga) The largest bolide impacts on the Earth and the Moon. Light gray filled boxes are lunar, black filled boxes terrestrial. Red line is inferred earth impact history. Dashed blue line is depth of ocean vaporized by impact. K/T refers to the Cretaceous/Tertiary impact and Ty refers to the lunar crater Tycho (From Sleep et al., 1989)
Life may have started during the heavy bombardment period • heavy bombardment, while rendering the ocean water column and any landmass that may have existed uninhabitable, would not have removed all water from the subsurface and thus would not have sterilized the Earth, but would have resulted in widespread impact‐volcanism (Abramov and Mojzsis, 2009).
Time of transition from anaerobic microbial ecosystems to aerobic microbial/eukaryotic ecosystems Mammals Humans Origin of Earth (4.5 Gya) Vascular plants Origin of life? Shelly invertebrates Thermophilic methanogens, S reducers 0 (thermophilic N-fixation) 4 1 Anoxygenic Billion years from photosynthetic human bacteria? (anaerobic) 3 Algal kingdoms 2 Cyanobacteria (the rise of O 2 ) Accumulation of O 2 Single celled eukaryotes (beginning of prey/predator associations?)
Life may have started during the heavy bombardment period • heavy bombardment, while rendering the ocean water column and any landmass that may have existed uninhabitable, would not have removed all water from the subsurface and thus would not have sterilized the Earth, but would have resulted in widespread impact‐volcanism (Abramov and Mojzsis, 2009).
Earth life requires the elements, vola$les and minerals produced as a result of tectonics and hydrothermal ac$vity
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