IV Convegno della Ricerca Italiana in Fisica Solare e

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CONSTRAINTS ON THE ORIGIN OF LIFE ON EARTH DUE
TO THE PHYSICS OF THE ANCIENT SUN J.
Chela-Flores The Abdus Salam ICTP, Trieste,
Italia Instituto de Estudios Avanzados, IDEA,
Caracas, Venezuela M. Messerotti INAF-Trieste
Astronomical Observatory, Basovizza, Trieste and
Department of Physics, University of Trieste,
Italia

• IV Convegno della Ricerca Italiana in Fisica
  Solare e
• Relazione Sole-Terra
• (18-20 Ottobre 2005)
• Sessione 6 - Relazione Sole-Terra Variabilita
  ed Attivita del Sole
• Giovedi, 19 Ottobre, 2005

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Sources of Space Weather
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The Voyayers (1 and 2)
NASA, 1977-1989
The Solar System Family
Europa
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Voyager I (94 AU)
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Sources of chemical evolution in the Solar System
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Compounds observed in the comas of comets
The Hale-Bopp comet
Some precursors of the biomolecules
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Organic compounds in meteorites
The Murchison meteorite
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The formation of the Earth
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Evolution of the early atmosphere

• During the accretional period, the Earths
  volatiles were released on impact, forming a
  transient steam atmosphere.
• At the end of the accretionary phase the Earths
  surface cools and the steam atmosphere produces
  an early hydrosphere, leaving an atmosphere of
  some 85 C.

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During of the first 100 Myr

• A model postulates a large hydrodynamic escape of
  H. Escaping H carries away heavier atoms by
  aerodynamic drag.
• The lighter isotopes are carried off more easily
  than the heavy ones. In post-accretion with
  decreasing EUV flux that was fueling the H
  escape, this process becomes difficult and
  eventually stops.
• The net effect is that the formation of the early
  Earth led to isotopic fractionation of the
  chemical elements.

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The fractionation of sulfurthe delta-34
parameterr

• (corresponding to the Canyon Diablo meteorite,
  CDM)
• This parameter has zero value when the sample
  (sa) coincides with the average terrestrial value
  of 34S/32S.

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Sulfur in the lunar dust from the Apollo missions
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The delta34S parameter in terrestrial, meteoritic
and lunar material

• According to measurements near the Californian
  coast
• S (insoluble), principally pyrite.

Terrestrial
Sulfate coexistenting with sea water
Meteoritic
Lunar
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Chemical element fractionation

• The delta 34-S parameter on lunar soils (and
  meteorites) is narrower than the corresponding
  cases of H, C and N.
• Hence, it may be the most reliable element for
  estimating biological effects.

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Solar radiation on the Earth as a challenge to
early microorganisms
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Microorganisms can survive large doses of
radiation
E. coli bacteria
Bacillus subtilis
Deinococcus radiodurans
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Life on Earth resistance to radiation
Survival of D. radiodurans after irradiation
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Europa(Galileo, 1995)
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Is life possible on Europa under Jupiters
ionizing radiation?

• A bacterium with the radioresistance of D.
  radiodurans would
• survive in 1 mm depth of the icy surface.
• The radiation environment at 40 m is similar to
  the Earth biosphere.

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Non-water ice constituents staining the icy
surface of Europa
New absorption features (?m) 3.50 3.88 4.05 4.25 4.57
Candidate elements H2O2 C2 H5 SH mercaptan SO2 CO2 (CN)2 cyanogen
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Conceivable sources of sulfur stains on the icy
surface of Europa

• External
• Ions may be implanted
• from the Jovian plasma,
• Internal
• Sulfur may be due to
• cryovolcanism, or we can
• ask
• Could sulfur be of biogenic origin?

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Measurements from the Ulysses dust detector (3.8
kg/consumes 2.2 W)in a second approach to
Jupiter in 2004
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Ios volcanic surface(Galileo)
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One way to decide on the S sourceLanding on
the icy surface of Europa
The Europa Microprobe In Situ Explorer (EMPIE)

• The lander will have a set of 4 miniprobes.
• Mass constraint for the microprobes 1.7 kg.

Tirso Velasco and colleagues
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Main phases of the descent

• Four light landers
• (350 gm each).
• Ejection from the orbiter.
• Penetration in ice 72.5 cm.

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Discussion

• Sulfur bacteria cannot in principle be ruled out
  as a source of the sulfur stains of the icy
  surface of Europa.
• If the sulfur source is biogenic, significant
  deviations from the CDM values of the
  delta34S-parameter should take place.
• Miniature gas chromatography-mass spectrometry
  (GC-MS) is appropriate for the detection of such
  biosignatures.

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Conclusions

• The collaboration of distinct sectors of the
  exploration of the Moon, the Galilean satellites
  and the Sun has taken place.
• This approach should lead to the identification
  of biosignatures of life.
• Hence, lifes origin could begin to be
  understood under the influence of the ancient Sun.