On the Chemical Composition of Europa s Icy Shell, Ocean and Unterlying Rocks

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1 On the Chemical Composition of Europa s Icy Shell, Ocean and Unterlying Rocks M. Yu. Zolotov (Arizona State University) J. S. Kargel (University of Arizona) By Isabella Kraus

2 Overview Introduction Composition of Icy Shell Brine, Salt and Gas Inclusions Chemistry of the Ocean-Rock System Basic Geochemistry of Ocean-Rock Interaction Salinity of Oceanic Water Chemical Evolution of the Water Layer Geochemistry of a Primordial Ocean Conclusion Isabella Kraus 2

3 Introduction Isabella Kraus 3

4 Introduction Isabella Kraus 4

5 Introduction Isabella Kraus 5

6 Introduction outer shell dominated by water ice ocean contains sulphate, Mg, Na, and Cl as major solutes ocean evolved from a reduced Na-Cl solution toward a Mg sulphate ocean Radioactive decay + tidal heating melting icy shell chemical information sparse at present surface oxidants (O 2, H 2 O 2 ) and possible H 2 SO 4 hydrate are likely products of radiolysis and photolysis Isabella Kraus 6

7 Introduction current icy shell formed through freezing of oceanic water oceanic composition affected by freezing from above, dissolution of minerals in underlying rocks, mineral precipitation, degassing processes and loss of volatiles to space Radiolysis, vapour cycling, gardening of the surface materials and injection of material from Io produced surface materials affected the composition of the deeper icy shell + ocean degassing of H 2, N 2, S and C volatiles from the icy shell influenced the composition and oxidation state Isabella Kraus 7

8 Introduction Mineral and/or organic precipitation isolated the suboceanic silicate crust from the ocean influenced the nature of ocean-rock interaction Euopa s moment of inertia composition and mineralogy of the interior Isabella Kraus 8

9 Composition of Icy Shell Isabella Kraus 9

10 Composition of Icy Shell non-ice within the icy shell geological structure of the shell tectonic processes caused by tidal motions and/or convection geologically young age of the surface reflects the time of significant ice melting/removal non-ice material concentrated in the upper part of the current (thick) shell a thicker shell disrupted less often and slower freezing would have led to less-efficient capture of oceanic solutes Isabella Kraus 10

11 Brine, Salt and Gas Inclusions icy shell contain salt, brine and gas inclusions formation solutions/gases formed in the icy shell upper ice layer radiolytically formed O 2 and CO 2 typical oceanic inclusion solids + contain aqueous (brine) and gas phases brine/salt inclusions contain abiotic or biogenic organic molecules Isabella Kraus 11

12 Brine, Salt and Glas Inclusions Isabella Kraus 12

13 Brine, Salt and Glas Inclusions Isabella Kraus 13

14 Brine, Salt and Glas Inclusions Isabella Kraus 14

15 Chemistry of the Ocean-Rock System Isabella Kraus 15

16 The nature of suboceanic rocks differentiated interior Fe or Fe-FeS core + silicate mantle upper parts of the mantle resisted melting affected by silicate due to gravitational instability tidal heating silicate melting and suboceanic volcanism uppermost mantle layers never affected by volcanism suboceanic rocks presented by accreted chondritic-type materials Isabella Kraus 16

17 The nature of oceanic sediments sizeable fraction Io s particles ejected by impacts carbonaceous-chondrite-type fragments ejacted from outer irregular satellites of Jupiter space materials late heavy bombardment Isabella Kraus 17

18 Salinity of Oceanic Water mass of dissolved salts per specified mass of aqueous solution balance of mineral dissolution, secondary precipitation and ionic exchange freezing larger effect on oceanic salinity than evaporation affected by thickness of the icy shell, the ocean and permeable rocks Reflect history, composition and oxidation state Isabella Kraus 18

19 Salinity of Oceanic Water maximum correspond to eutectic compositions Freezing leads to near eutectic salinities of several hundreds of g/kg lower limits assuming saturation with respect to sparingly soluble secondary minerals in suboceanic rocks thin icy shell ( km thick ocean) not consistent with extremely high salinities at the salt saturations correspond to near-complete freezing Isabella Kraus 19

20 Salinity of Oceanic Water low tidal activity freezing of the icy shell, increasing salinity of oceanic water, mineral precipitation and exsolution of dissolved gases higher salinities depress freezing temperatures + imply colder oceanic water Isabella Kraus 20

21 Chemical Evolution of the Water Layer Isabella Kraus 21

22 Geochemistry of a Primordial Ocean warming by radioactive decay more melting of ice composition formation subject to low-temperature (0 C) composition of aqueous fluids dissolution of minerals very early fluids low ph some of the models there is not much subsequent waterrock interaction other models there is extensive water-rock interaction Isabella Kraus 22

23 Conclusion chemical information sparse models suggest: 1) Hydration + oxidation in the upper parts of the mantle 2) preferential accumulation of Cl, Br, I and Na in a water ocean 3) alkaline ph of ocean-entering fluids reactions with minerals 4) oceanic sediments affected by the degree of freezing of the water shell 5) low-temperature redox disequilibria among solutes, solids, and gases 6) accumulation of carbonate in the outer layers of the body 7) escape of low-solubility volatiles (H 2, N 2, CH 4 noble gases) into space Isabella Kraus 23

24 Literatur =oyxbubdoco3bsgaf0idabw&ved=0cacq_auoaq&biw=1045&bih=516#facrc=_ &imgrc=3lrknaoiygjram%3a%3bnq8k4zi61frtrm%3bhttp%253a%252f%252fw ww.seasky.org%252fsolarsystem%252fassets%252fanimations%252fsystem_menu_jupiter.jpg%3bhttp%25 3A%252F%252Fwww.seasky.org%252Fsolar-system%252Fjupitermenu.html%3B910%3B450 Buch: Europa (On the Chemical Composition of Europa s Icy Shell, Ocean, and Underlying Rocks) Isabella Kraus 24

25 Danke für Ihre Aufmerksamkeit!

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