the importance of radioactive sources for the origin of ... · if a system in equilibrium is...

Thiago Altair, Marcio G. B. de Avellar, Fabio Rodrigues, Douglas Galante

The Importance of Radioactive Sources for the Origin of Life and the Habitability of Icy

Moons in the Solar System

AstrobiON / October 2018

Environmental and Planetary Sciences

!1

[email protected]

BiosignaturesDetection and characterization of life


Molecular


Molecular

Mineral


Molecular

Mineral

Morphological


Molecular

Mineral

Morphological

How did this all begin?

Some very old forms of life...

3

1 µm

Mink Mountain Gunflint chert

Vida ?

Life’s building blocks

Life’s building blocksWater

Nucleic acids

Aminoacids

Lipids

Carbohydrates


Nucleic acids

Aminoacids

Lipids

Carbohydrates

CHONPS


Nucleic acids

Aminoacids

Lipids

Carbohydrates

CHONPS+ disequilibrium

Extraterrestrial life

Geological time

A planet of bacteria

SECO

Extremophiles

The deep environment of icy moons

12

The deep environment of icy moons

12Galileo old data reanalysed (2018) ! Europa plumes!

14

Europa Clipper / JUICE

Europa

15

Europa• Icy moons: We can find liquid water in abundance, mesophilic

temperatures. The oceans under the icy crusts may present biophilic environments.

15



• Exogenous and endogenous sources of energy

15




• Source of biological energy: direct radiolysis of water by primordial radioactive elements accumulated in these moons in the beginning of the Solar System history.

15




• Source of biological energy: direct radiolysis of water by primordial radioactive elements accumulated in these moons in the beginning of the Solar System history.

15

We perform a thermodynamic analysis to demonstrate that it would be possible to attain

enough chemical energy to sustain na extremophilic ecosystem.

Motivation: natural nuclear reactors

16

Motivation: natural nuclear reactors

3Gyr ! ~3% U235

Oklo

16

Water radiolysis

thorianite

uraninite

17

Water radiolysis

thorianite

uraninite

17

α

γ

β

Water radiolysis

𝐹𝑒𝑆2 + 4𝐻𝑂• → 𝐹𝑒2+ + 𝑆 + 𝑆𝑂−24 + 2𝐻2

thorianite

uraninite

17

α

γ

β

Sulfate biochemistry

4𝐻2 + 𝐻+ + 𝑆𝑂2−4 → 𝐻𝑆− + 4𝐻2𝑂

Desulfovibrio vulgaris

18

19

A special extremophile

• Mponeng gold mine in South Africa

19



• 2.8 km deep

19



• 2.8 km deep• Gram positive sulfate-

reducing bacterium

19




reducing bacterium• Carbon and nitrogen fixation

19




reducing bacterium• Carbon and nitrogen fixation• 60 °C and pH of 9.3

19




reducing bacterium• Carbon and nitrogen fixation• 60 °C and pH of 9.3• Single species ecosystem

19




reducing bacterium• Carbon and nitrogen fixation• 60 °C and pH of 9.3• Single species ecosystem• Radiophilic (?!) bacteria

19





19

Julio Verne’s Journey to the Center of the Earth

Descende, audax viator, et terrestre centrum attinges (Descend, bold traveller, and you will attain the center of the Earth)





19

Julio Verne’s Journey to the Center of the Earth

Descende, audax viator, et terrestre centrum attinges (Descend, bold traveller, and you will attain the center of the Earth)


A survivor from the LHB?

20

D.Audaxviator metabolism

A simplified metabolism

21

Radiolysis modelling for Europa

22


22

1) Metabolism of Desulforudis audaxviator

2) 238U, 232Th, 40K abudances for radiolysis

3) Experimental rate of production of SO42− via oxidation of

pyrite

! Europan deep ecosystem carrying capacity

(⋆) Here we are exploring an internal souce for SO42−, not

exogenous.


23

The rate of production of this anion via radiolysis is given by

Where

• Gs = 2.1 × 10−9 mol/m2/(J/kg) (experimental value) is the efficiency of the sulfate production via radiolysis ;

• Di =EiλiciNaA−1 [J/kg/year] is the radiation dose rate for the various species i;

• E [J /decay ] is the energy per decay corrected by neutrino loss ; • λ = 1/t1/2 [decay /year ] is the decay constant; • c [ppm] is the concentration of the radioactive element ; • Na = 6.022 × 1023 is the Avogadro’s number ; • A [g/mol] is the atomic mass

𝒀 = ∑𝒊

𝑫𝒊 × 𝑮𝒔


23

The rate of production of this anion via radiolysis is given by

Where

• Gs = 2.1 × 10−9 mol/m2/(J/kg) (experimental value) is the efficiency of the sulfate production via radiolysis ;

• Di =EiλiciNaA−1 [J/kg/year] is the radiation dose rate for the various species i;

• E [J /decay ] is the energy per decay corrected by neutrino loss ; • λ = 1/t1/2 [decay /year ] is the decay constant; • c [ppm] is the concentration of the radioactive element ; • Na = 6.022 × 1023 is the Avogadro’s number ; • A [g/mol] is the atomic mass

𝒀 = ∑𝒊

𝑫𝒊 × 𝑮𝒔

The annual production of radiolitic sulfate is given by Ps = Ys × Spy, where Spy [m2/kgrock] is the surface area of pyrite per kilogram of sedimentary rock.

Results

24

Our numbers are :

• 0.056 to 15 ppm of 232Th ; • 0.016 to 271 ppm of 238U ; • 380 to 3800 ppm of 40K;

*we assumed pyrite concentration of 5 wt.% and pyrite surface area of 1.13m2/kgrock

Results

24

Our numbers are :



Europa?

Results

24

Our numbers are :



Our result is, then,

Ps = 0.82 − 8.2 nM/year,

which is of the same order or one order of magnitude greater than the minimum necessary for the survival of the D.audaxviator.

(⋆) Important remark : models for the origin, composition and evolution of the crust and ocean of Europa suggest the formation of pyrite-like materials, being these a major component.

Europa?

Close-packing modelGeological dependence of pyrite availability


Type of aggregat

eGrain d(µm)

Spy(d) (m2.kg-1)

Clay 2 1.41×103

Silt10 2.83×102

60 4.71×101

Sand125 2.26×101

500 5.651000 2.83

Pebbles 10000 2.83×10-1

50000 5.65×10-2

Cobbles 100000 2.83×10-2

200000 1.41×10-2

In summary

26

In summary

26

• From calculation for Europa it is possilbe to provide at least as much energy as the necessary only by the γ decay of 40K since its abundance can be 10 times (or more) greater than that found on Earth oceans.

In summary

26


• This result makes Europa a propitious place for the development of an ecosystem that sustains simple forms of life like the sulphate-reducing bacteria Desulforudis audaxviator.

In summary

26



• Our results also make of Europa a good place for searches for extraterrestrial forms of life.

In summary

26



• Our results also make of Europa a good place for searches for extraterrestrial forms of life.

• Habitable zones extented to radioactive environments!

Fontes hidrotermais Origin of life?

Sphere in movement

Example of equilibrium

Sphere in movement


Out of equilibrium


Out of equilibrium


In equilibrium

Static equilibrium


In equilibrium

In summary...Reactants Products


Chemical equilibrium


Chemical equilibrium

Important: From thermodynamics, the chemical equilibrium will only happen when the procces is not sponteneous in any direction!

If a system in equilibrium is disturbed by an alteration on concentration, temperature or pressure of one of its componentes, the system will move its equilibrium position in a way to balance the effects of perturbation.

Le Chatêlier principle

Henry Louis Le Chatêlier (1850-1936)

Químico francês

Lost Cityhydrothermal system

• Off-axis mid-ocean rige

• Moderate temperatures (~60 - 120oC)

• High pH (10): strong gradient

• Source of H2 and CH4

• Fe and S available • Microenvironment and

compartimentalization

37

38

Volcanic CO2

38

Volcanic CO2

H2 hidrothermal

38

Global electrochemical cell

Volcanic CO2

H2 hidrothermal

Natural radioactive environments as sources of local disequilibrium for the

emergence of life Thiago Altair, Larissa M. Sartori, Fabio Rodrigues, Marcio G.

B. de Avellar, Douglas Galante

44

livro.astrobiobrasil.org 45

[email protected]

the importance of radioactive sources for the origin of ... · if a system in equilibrium is...

Documents