Hadean-Archean Habitability

Hadean - Early Archean: 4.4 to ~ 3.5 Ga How to build a habitable planet?

Jack Hills in Australia meta-conglomerat with the oldest minerals on Earth 4.4 Ga Geological time scale

1 : Hadean 2 : Archean

Quasi no rock record Rock record First cooling of magma ocean

Alteration of basalt to produce serpentinite crust ~ as today on seaﬂoor

146 142 Sm → Nd (T1/2= 103 Ma) silicate/silicate fractionation before total decay of 146Sm ⇒ < 150 Ma, done early Hadean Acasta (Canada) oldest rocks on Earth, end of Hadean, 4.01 Ga Acasta (Canada) oldest rocks on Earth, end of Hadean, 4.01 Ga Acasta (Canada) oldest rocks on Earth, end of Hadean, 4.01 Ga

Zircon ages Jack Hills (Australia) meta-conglomerat Archean in age but contains very old zircons Jack Hills (Australia) meta-conglomerat Archean in age but contains very old zircons Jack Hills (Australia) meta-conglomerat Archean in age but contains very old zircons

ZrSiO4

1 mm U-Pb age at 4.4 Ga Part of the grain crystalized shortly after end of magma ocean Age distribution of zircons

Different dates on different zircon layers

Several age populations

Oldest Quartz, micas and plagioclase ∂18O in zircons = 5 to 7.4 ‰ Original magma’s = ∂18O ~ 8.5 to 9.5‰

(La/Lu)N zircons⇒(La/Lu)N of magma~ 200 = TTG magma

4.4 Gyr zircons not so different from actual zircons Granitic inclusions present in zircons

Quartz, micas and plagioclase ∂18O in zircons = 5 to 7.4 ‰ Original magma’s = ∂18O ~ 8.5 to 9.5‰

(La/Lu)N zircons⇒(La/Lu)N of magma~ 200 = TTG magma

4.4 Gyr zircons not so different from actual zircons

Continental crust & oceans in Hadean

Granitic inclusions, quartz, micas, plagioclase La/Lu data same as Archean crust Stable continental crust at 4.4 Ga ∂18O indicates that magma interacted with relatively cold water (~ 70 ºC) Liquid water is present Ocean present at 4.4 Ga

Looks like Hadean already was habitable “cool early earth” (but was it inhabited?) Implications for the origin of life

Early Hadaen (4.568-4.40 No life possible Ga) Magma Ocean

Late Hadaen (4.40- 4.00 Conditions favorable Ga) Continental crust + liquid water for life ocean

Late heavy bombardment Sterilization ??

Archean (4.00 – 2.50 Ga) Life is present Continents, oceans, plate tectonic, etc. Between 4.0 and 3.8 Ga Late heavy bombardment

Between 4.0 and 3.8 Ga Collisions - impacts all over solar system NASA deep impact Hubble ST Fragment G impact

Asteroid Eros 1 km 1994 Shoemaker-Levy 9 on Jupiter 33x13x13 km Surface comet Tempel 1

Mare Orientale on the Moon ~ 930 km multi-ring crater 140 km crater on Europa’s ice Collisions - impacts all over solar system NASA deep impact Hubble ST Fragment G impact

Asteroid Eros 1 km 1994 Shoemaker-Levy 9 on Jupiter 33x13x13 km Surface comet Tempel 1

Mare Orientale on the Moon ~ 930 km multi-ring crater 140 km crater on Europa’s ice Collisions - impacts all over solar system NASA deep impact Hubble ST Fragment G impact

Asteroid Eros 1 km 1994 Shoemaker-Levy 9 on Jupiter 33x13x13 km Surface comet Tempel 1

Mare Orientale on the Moon ~ 930 km multi-ring crater 140 km crater on Europa’s ice Cratering event on solid surface Cratering event on solid surface Cratering event on solid surface Cratering event on solid surface

Suevite Cratering event on solid surface

Suevite

Melt-rock Cratering event on solid surface

Suevite

Fractured breccia

Melt-rock Cratering event on solid surface

Shocked minerals

Suevite 100 µm

Fractured breccia

Melt-rock Tektites Cratering event on solid surface

1 cm

Shocked minerals

Suevite 100 µm

Fractured breccia

Melt-rock 3.4 Comparative stratigraphy of 3.5 Early Earth and Mare Lavas 3.6 Moon Orientale 3.7 Schrödinger Nulliak Quartzite 3.8 Cluster of Lunar Imbrium Early Amitsôq Gneiss Imbrian craters around Sereniatis LH B Isua Gneiss & Crisium 3.9 4.0 to 3.8 Ga Nectaris 4.0 Oldest Acasta Gneiss impact melt 4.1

4.2

4.3

4.4 Oldest Jack Hill Zircon Anorthosite crust Origin of 4.5 Origin of Moon Earth Late heavy bombardment

2 hypotheses Slow decline

Rapid decline but short peak

Cool early earth Another ? Archean rate

Hadean Archean Arguments for the LHB ~ 3.9 Ga max. age of Lunar impact melt and = shock degassing ages of Lunar and Martian meteorites

How to preserve ancient Lunar crust (4.4 Ga old anorthosites) if elevated bombardment in Hadean ?

No elevated PGE in Lunar crust contrary to what expect if bombardment constant over 500 Myr (based on available samples)

LHB = mass added to the Moon = 2x1013 g/an if extrapolated over whole Hadean > Lunar mass or Moon formed at ~4.1 Ga

Terrestrial zircons do not show shock features and formed on a rather cool Earth Traces of LHB on Earth ? No impact marker in Isua (shocked qz, PGE)

LHB missed Earth ?

Chronology problem: LHB terminated before Isua

Traces erased by sedimentation and erosion

Search for it on other planets Extrapolate Moon data to Earth Moon: 1700 craters > 20 km, 15 > 300 -1200 km, multiple ring basins

Earth: > 10 000 craters > 20 km, 200 > 1000 km, 1 crater 20 km every 104 years

Possible consequences

Vaporize all of part of oceans, ejection of atmosphere

Large basins are formed

Volcanism, fracture of oceanic crust

Contribution of OM, and noble gases Impact rate and Hadean environments Hadean impact rate is elevated no life possible (hyp. 1)

Cool early Earth hypothesis and effect of LHB

Low impact rater : life originates in Hadean (hypothesis)

Complete extinction during LHB, second start in Archean

Major Hadean diversiﬁcation but mass extinction during LHB, only hyperthermophiles survive on deep ocean ﬂoor, and radiate in Archean

Major Hadean diversiﬁcation but mass extinction during LHB, bottleneck effect, new radiation during Archean Origin and cause of LHB

Models show that 0.350 to 1.2 Ga after formation of solar system, gas planets migrate towards their current orbits (Jupiter and Saturn inward, Neptune and Uranus outward)

Destabilize orbits of asteroids and comets

Objects come ﬂying towards inner solar system Impact craters (basins) as a craddle for life ? hypothesis of origin in hydrothermal vents handicaped by high vent Tº > 350 ºC destroys all organic molecules

Melt-rock generates hydrothermal circulation Important extension of hydrothermal environments in the crater, life > 106 year, enough to concentrate complex organic molecules Ries (25 km), Manson (35 km) and Puchezh-Katunki (80 km) mineralogy show temperature gradients 400 to < 100°C. Crater contains highly fractured and brechiated rocks, inducing active circulation and micro- environments with exposed mineral surfaces to favorable help catalyze pre-biotic chemistry Complex organic molecules delivered by the projectile

Yellowstone Geyser system, complex biosphere Stromatolites ﬁrst form to recolonize Ries crater lake Do complex organic molecules survive an impact ?

Complex organic molecules are destroyed by the high temperatures generated by impact (Chyba et al., 1990)

Still valid for asteroidal projectile at ~ 20 km/s

Computer model : amino acids survive a cometary impact in the ocean

Comet volatile and ice-rich, easily vaporized but the high energy cloud cools rather quickly

The lower the impact angle, the lower temperature in the cloud, the higher the survival rate of organic molecules Text

Oblique (angle < 15°) impact of a comet in the ocean could spread (> 10%) of its amino acid content

Such impacts are rare, but considering impact rate in the Hadean or during LHB, they could have contributed to the concentration/reaction of amino acids in the oceans

Association amino acids and altered clay particles (spherules) offer surface for pre-biotic chemistry ? Archean impact rate ? Ejecta layer Location Age (Ga) Thickness cm

Acraman Australia 0.59 40 Sudbury Ontario 1.86 25 to 70 Ketilidian Greenland ~ 2.0 100 Dales Gorges Australia 2.48 30 Wittenoom Australia 2.54 100 Revilio Australia 2.56 20 Carawine Australia - S. Africa 2.63 2470 S4 (Barberton) South Africa 3.24 15 S3 (Barberton) South Africa 3.24 200 S2 (Barberton) South Africa 3.26 310 S1 (Barberton) South Africa 3.47 35

KT World 0.065 few cm (to 1 m) Archean and Proterozoic impact layers

1 cm

0.5 mm

Impact ejecta layer Wittenoom, Australia

Comparison Cretaceous-Tertiary layer 10 km impact 65 Ma ago Archean and Proterozoic impacts Ejecta layers thick and with large impact spherules, PGE anomaly but rare shocked grains

Spherule composition originally basaltic, associated with tsunami deposition

Large size impacts: > KT boundary, projectiles 20 to 50 km?

Oceanic impacts ?

Detection coincidence ? impact rate > today, peak in bombardments ?

How did life cope with elevated rate ? Geological time scale

1 : Hadean 2 : Archean

Quasi no rock record Rock record Archean continental crust: a long record Isua gneiss, sedimentary rocks, Greenland dated at 3.865 Ga

Deposited as turbidite Amitsôq gneiss, plutonic rocks, Greenland dated at 3.82 Ga

Magmatic origin Current distribution of Archean terranes Gneiss of Shaw (Australia) at 3.45 Ga Swaziland gneiss complex at 3.644 Ga Greenstone belts

Banded Iron formation Barberton, komatiite, Gopping Gap, Pilbara, South Africa Australia 3.445 Ga 3.5 Ga

Chert, Barberton, 3.445 Ga Pilbara, Australia 3.5 GA

Shark bay Australia today Are these equivalent to stromatolites ?

Films of Cyanobacteria trapping sedimentary grains in shallow water environments Greenstone belts

Tholeitic basalt Grauwackes Kuhmo, Finland Kuhmo, Finland 2.65 Ga 2.65 Ga Late Plutonic rocks

Granodiorite of Arola, Finland 2.65 Ga Proportion of Archean terranes

Kuhmo, Finland 2.7 Ga

Arola, Finland 2.7 Ga Gurur, India 3.1 Ga Komatiites: evidence for a warmer Archean Earth

Magmatic rock that does not exist after end of Archean

1 cm 1 cm Komatiites = equivalent to ridge basalts ?

Komatiites = ultra basic lava’s SiO2 = 45%, MgO = 25%

High density

Elevated proportion of mantle fusion

Formation Tº are very high ~ 1650 ºC

Originated from deep within the mantle, contain diamonds

Only present in the Archean

Warmer mantle need, now too cold to generate komatiites Archean continental crust

Rocks Tdh = Trondhjemite To = Tonalite TTG Gd = Granodiorite Archean crust versus today’s crust

Archean TTG Calco-alcaline crust of today Fundamental differences in magmatic processes between Archean and today

H2O released Hot plate melts lowers melting point

Subduction today Archean subduction of a hot plate a cold plate sinks below another that melts quickly and dry wet melting generates magma Higher mantle fusion & different plate tectonic Very long angle subduction

Buoyancy of both plates is almost same 4.0 Ga ago the Earth internal heat production was 4 x higher than today

To avoid melting, the heat must be evacuated:

- Faster mantle convection - Longer ridge length

Intense magmatism and hydrothermalism

Black smoker Size of Earth is constant, consequently longer ridge length implies much smaller plates

Current Archean average plate size = >>1000 km average plate size = ~ 100 km Pilbara craton Australia

Dome and basin structures evidence for vertical tectonic Vertical tectonic, soft cheese principle

Heavy lithologies sink in the softer underlying rocks Summary Archean plate tectonic

Mini-plates Rapid plates

Low angle subduction

Very long oceanic ridges

Intense hydrothermalism

Dry melting of hot plate in subduction

No major mountain belts, soft cheese principle Emerged continents ? Continents above water in Archean At 3.86 Ga in Isua presence of detritic sediments most likely eroded from continent located above water

Conglomerat in Barberton, difﬁcult to form under water Fossil dessication Dessication cracks cracks from Barberton At 3.4 Ga Barberton lithologies contain garnet recording pressure 15kbar (~ 45 km depth in crust today) Some kind of mountains existed, how high ? Growth of crustal material

Wilson cycle-like? First traces of life

Earth Moon

2.5 Ga Window origin of life 3.8 Ga

Metamorphism renders microfossil and C isotopic evidence ambiguous > 2.7 Ga The tracers: 1) Morphological fossils: microfabrics, stromatolites

A) Endolithic C ) A b i o l o g i c coccoids in a m i c r o s t r u c t u r e crack of an 3.8 p r o d u c e d i n t h e G a I s u a B I F laboratory (Garcia- samples Ruiz et al., 2003). (Westfall & Folk, 2003)

B) Carbonaceous microstructure in Apex chert (3.4 Ga) either microfossil “ballerina” or a pure metamorphic process of mineral mimicking biology (Brasier et al. 2002)

2) Molecular fossils: derived from cellular macromolecules, ex. lipids, steranes, hopanes but : very small quantities preserved with major risk of contamination (Brocks et al. 2003) there is not clear record < 2.7 Ga because of metamorphism

3) Isotope ratios: ex. ∂13C or ∂34S : ∂13C = ([(13C/12C)sample/(13C/12C)std]-1)*1000 Carbonates ∂13C = 0‰ and remains of biological material = ~ -25 0‰ Consequently low ∂13C values in Archean sediments could indicate life but: graphite forming abiologically during metamorphism also has low ∂13C ! There is nothing conclusive before 2.7 Ga The tracers: 1) Morphological fossils: microfabrics, stromatolites

A) Endolithic C ) A b i o l o g i c coccoids in a m i c r o s t r u c t u r e crack of an 3.8 Controversial p r o d u c e d i n t h e G a I s u a B I F laboratory (Garcia- samples Ruiz et al., 2003). (Westfall & Folk, 2003)

B) Carbonaceous microstructure in Apex chert (3.4 Ga) either microfossil “ballerina” or a pure metamorphic process of mineral mimicking biology (Brasier et al. 2002)

1 µm 5 µm

Bacterial ﬁlament in Modern Leptothrix Fe- Eoentophysalis Modern Eoentophysalis Gunﬂint Chert 2.5 Ga bacteria cyanobacteria in Early Proterozoic cherts

Along with isotopic evidence of advanced metabolism 2+ reduced chemical species: CH4, H2, S, H2S, Fe , chemoautotrophic, followed soon after by photosynthesis Diversiﬁcation of metabolism a possible scenario ? The rise of O2 between ~ 2.4 to 2.0 Ga The great oxidation event Lots of debates currently on exact timing and consequences O2 producers could have originated earlier but rise in O2 was delayed by various processes: tectonic, burial Corg., unstable climate etc.

Fractionation of S isotope is mass independent under UV photolysis when no O3 layer and for -5 O2 < 10 PAL After 2.3 Ga when O2 present in atmosphere normal mass dependent fractionation of S Oxidized paleosols, red beds are present Decrease in BIF that form in anoxic oceans, no more precipitation of Fe Evaporite deposits, and carbonates increase signiﬁcantly Consequences for organisms

O2 poisoning, extinction or refuge in anoxic environments, less methanogenesis Radiation of photosynthetic organisms, replacement, new metabolism, new possibilities Stromatolites become very abundant (but perhaps already present around 2.8 Ga?) Consequences for climate

1st : faint young sun paradox: between 4.0 Ga and today sun’s increased it luminosity by 37%

If the Earth had same atmosphere as today it would have been frozen until ~ 2.0 Ga. Sun However no (or very few) traces of glaciations (diamictite, isotopic signals) in the Archean

Evolution of luminosity of 3 stellar masses through time

Lots of greenhouse gas would keep Earth warm

CO2 but also CH4, in absence of O2, methanogenesis (considered a early metabolism) occurring in anoxic conditions would be highly efﬁcient capable to sustain warm climate:

If Archean atm = today’s (without O2) the CO2 + CH4 PAL leads to average Tº < -10 ºC, CH4 must rise to 10 PAL = T 0ºC, 100 PAL = T 5ºC and 1000 PAL = T 15ºC average Consequences for climate

Rise of O2 would affect production of the main greenhouse gas CH4 by restricting progressively anoxic environments

Less and less CH4 in atmosphere, CO2 cannot compensate, most likely also decreases Glaciations results: Clear evidence ﬁrst phase at 2.9 Ga (Pongola glaciation), then Huronian

glaciations 3 events between 2.45 and 2.32 Ga, matches rising of O2 At 2.2 Ga evidence for low latitude Makganyene glaciations = First Snowball Earth ?

What is a snowball Earth ?

Glaciations extending down to equator runaway ice albedo feedback drops Tº to -50ºC for a few 1000 y, then Tº stabilizes around -10ºC after million of years of ice cover the lack of silicate weathering + volcanic emissions lead to CO2 greenhouse effect in atmosphere and melting of ice, it is followed by global tropical conditions (see Hoffman et al. 1998).