Julian Chela-FloresThe Abdus Salam ICTP, Trieste, Italia and Instituto de Estudios Avanzados, Caracas, Republica Bolivariana de Venezuela

Can a future mission detect a habitable ecosystem on Europa, or

Ganymede?

Io

Europa

Ganymede

EJSM (JGO)

EJSM (JEO)

Callisto

The Europa Jupiter System Mission (EJSM)

Top questions:Top questions:

The search for habitable ecosystems (a question in geochemistry, 1970s, Vikings).

The search for the origin of life itself (a question in chemical evolution, 1920).

Top questions:Top questions:

The search for habitable ecosystems (a question in geochemistry, 1970s, Vikings).

The search for the origin of life itself (a question in chemical evolution, 1920).

Can we identify reliable biomarkers on Europa with

EJSM?

Oceans in contact with silicate cores in the Oceans in contact with silicate cores in the Solar SystemSolar System

Working hypothesis: The ocean-core interface can provide a variety of chemical elements for sustaining life.

Europa

Ice-core interface

Earth

Ocean-core interface

The geochemistry of Europa:The geochemistry of Europa:

____________________________________________________________ There is a unique opportunity to There is a unique opportunity to

focus on another Earth-like world focus on another Earth-like world with EJSM by probing 1 and with EJSM by probing 1 and confirming 2:confirming 2:

________________________________________________________________

2. Liquid ocean in contact with its silicate core

1. Stained icy surface

Plan of the talkPlan of the talk

Analysis:Analysis: • 1. The stained icy surface of Europa. 1. The stained icy surface of Europa.

• 2. The liquid Europan ocean in contact with its 2. The liquid Europan ocean in contact with its silicate coresilicate core..

Conclusions:Conclusions:

• Instrumentation for identifying reliable biomarkers. Instrumentation for identifying reliable biomarkers.

• An EJSM test for a habitable ecosystem on EuropaAn EJSM test for a habitable ecosystem on Europa ..

1. The stained icy surface of 1. The stained icy surface of EuropaEuropa

International Journal of Astrobiology (April, 2010)(Cambridge University Press).

There are alternative views on the effect of space weather on the surficial patches. But S is common to both

interpretations of the radiation-induced S-cycles produced on the surface.

Galileo Mission, 1995-2003

To get insights into the significance of the sulfur patches on the icy surface of Europa, we should look at the sulfur patches on icy terrestrial surfaces.

What do we know about sulfur icy patches on Earth?What do we know about sulfur icy patches on Earth?

AntarcticaAntarctica

C: Canada GlacierC: Canada GlacierF: Lake FryxellF: Lake FryxellH: Lake HoareH: Lake Hoare

Taylo

r Val

ley

Taylo

r Val

ley

Underneath the surface of these lakes

Algal mat pieces

The icy surface of Lake Hoare The icy surface of Lake Hoare (Taylor Valley)(Taylor Valley)

Algal mat pieces on the surface of Lake Hoare

(Parker et al, Phycologia, 1982)(Parker et al, Phycologia, 1982)Algal mat pieces

Algal mat pieces

The larger Taylor Valley lakes

Biogenic sulfur on the icy surfaces of Taylor Biogenic sulfur on the icy surfaces of Taylor valley valley lakeslakes

(5.4 sq.km)(1.8 sq. km)( )

[Annual escape of biogenic sulfur (kg)]

2. Implications of Europa’s ocean 2. Implications of Europa’s ocean in contact with its silicate corein contact with its silicate core..

• External Jovian magnetosphere source, is External Jovian magnetosphere source, is excluded due to the patchy nature of the excluded due to the patchy nature of the stains.stains.

• Internal source:Internal source:

Cryovolcanism, or biogenic.Cryovolcanism, or biogenic.

• Geochemistry allows to select between Geochemistry allows to select between these two possibilities.these two possibilities.

The biogenic The biogenic hypothesishypothesis

Sulfate-reducing bacteriaSulfate-reducing bacteria

4H4H22 + H + H22SOSO44 –» H –» H22S + 4HS + 4H22O + 39 O + 39 kilocalorieskilocalories

The HThe H22S then combines with Fe in sediments to form grains of S then combines with Fe in sediments to form grains of the biogenic mineral pyrite.the biogenic mineral pyrite.

Unite H with S atoms from dissolved sulfate ( SOUnite H with S atoms from dissolved sulfate ( SO44-2 -2 ) )

of seawater to form hydrogen sulfide Hof seawater to form hydrogen sulfide H22S :S :

Iron sulfide, FeS2

Processing sulfur in the Solar Processing sulfur in the Solar SystemSystem

Dissolved sulfate: Dissolved sulfate: on evaporation on evaporation sulfate minerals are sulfate minerals are depleted of depleted of 3232S by S by 20 per mil.20 per mil.

The HThe H22S given off S given off by S-hungry by S-hungry bacteria is enriched bacteria is enriched in in 3232S by 20 per mil.S by 20 per mil.

Large depletion:

Microbial single-step large sulfur fractionation

Biogenic S on icy surfacesBiogenic S on icy surfaces

Terrestrial

Meteoritic

Lunar

-70 per 70 per millmill(extreme (extreme fractionation)fractionation)

The Integrated Ocean-The Integrated Ocean-Drilling Program Drilling Program (IODP) (IODP) while while exploring exploring terrestrial structure has terrestrial structure has identified identified extreme extreme fractionation fractionation on the on the Australian seafloor.Australian seafloor.

Modern sulfate Modern sulfate coexisting coexisting

with ocean waterwith ocean water(21 per mill)(21 per mill)

The deltaThe delta3434S-parameterS-parameter

Large, and even Large, and even extreme extreme depletiondepletion of sulfur takes of sulfur takes place on terrestrial place on terrestrial ecosystems.ecosystems.

((per millper mill)) (per mill)(per mill)

Instrumentation required for identifying reliable biomarkers

Credit: Credit: British ConsortiumBritish Consortium

Penetrators for probing Europa’s icy surfacePenetrators for probing Europa’s icy surface

Credit: Credit: British British ConsortiumConsortium

Gowen et al., 2009

Penetrators should be inserted in the EJSM orbital probes: JEO and JGO.

To answer what is the meaning of the Europan icy patches we should go beyond measurements from JEO alone

for detection of biomarkers.

lloowweerr vvaalluueess

ooff

33

44

SS..

Both JEO and JGO can test biogenicity with two sets of penetrators

JGO +penetratorJEO+penetrator

Ganymede, ESAEuropa, NASA

An EJSM test for a habitable ecosystem An EJSM test for a habitable ecosystem on Europaon Europa

We expect diverging results from mass We expect diverging results from mass spectrometry:spectrometry:

— — large minus large minus 3434S for Europa, and S for Europa, and

— — small minus small minus 3434S for Ganymede.S for Ganymede.

Such data would provide a test of a habitable Such data would provide a test of a habitable ecosystem on Europa.ecosystem on Europa.