Will exobiology out of the Solar System stop after the DARWIN mission

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Will exobiology out of the Solar System stop
after the DARWIN mission ?

• Marc Ollivier(1), Alain Léger (1), Pascal Bordé
  (2) and Bruno Chazelas (1)
• (1) Institut dAstrophysique Spatiale dOrsay
• (2) IPAC - Caltech

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DARWINs quest first order spectroscopy

• Pleurant, je voyais de l'or, - et ne pus boire.
• (A. Rimbaud)

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1What is the composition of the planetary
atmosphere ?Is it primitive or did it evolve
?What about bio-markers ?
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Infrared spectral range
Selsis, ESA SP 518, 2002
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Multi criteria spectral analysis

• Requires low res. spectra (r20-50), moderate S/N
• Theory / observation e.g. CO2, H2O , O3
  (Selsis)
• Simultaneous presence of oxidizing / reducing
  gases (ex CH4 and O2, NH3 and O2,) (Sagan)

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High resolution spectroscopy

• Specific spectral features
• at (r200-500)
• e.g technological gases
• Observation still at the planet
• scale
• S/N depending on the features
• Pb of contaminations by other
• species

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High resolution spectroscopy how to ?

• Required spectral resolution 200 - 500
  DARWIN x 20
• Required S/N 100 DARWIN x 10
• Signal 10 ph / s / m2 in 6-20?m

• Assuming the same performance for the instrument
  (transmission, rejection, stability)
• Assuming integration times x 5
• Collecting area x 400 i.e diameter x 20
• -gt ELT in space
• -gt Improvement in the instrument performance
• -gt classical imaging coronagraph
• -gt other concept ?

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High resolution spectroscopy how to ?

• Angular résolution 0.1 arcsec at 10 ?m -gt
  20-40 m class telescope
• Collecting area compatible
• High performance coronagraph
• Global efficiency x 10 at least
• No need for hyper telescope
• -gt  BIG  NGST

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2What about the surface ?Are there evident
traces of life activity on the planetary surface
?Can we image them ?
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Direct imaging hypotheses

• Image of an earthlike planet
• Planet distance 10 pc earth diameter 8.5
  10-6 arcsec
• S/N 10 per pixel
• Integration time reasonable (?!)
• Collecting area 20000 m2 (equ. 10 x 50m
  telescope)
• Planet photon limited observations (100 pl.
  photons req)
• No planet rotation during exposure (or elementary
  exposure)
• Pb day / night for the planet (phases)
• Visible spectral range 0.5 -gt 1 ?m, mean
  wavelength 0.75 ?m total flux in the spectral
  band 0.1 ph / s / m2
• Efficiency of the detection chain (detector
  incl.) 20

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Direct imaging
16 x 16 -gt 200 px Res 4. 10-7 arcsec -gt 450
km Int. Time 1 min - 3min
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Direct imaging (2)
32 x 32 -gt 800 px Res 2. 10-7 arcsec -gt 900
km Int. Time 3.5 min - 10 min
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Direct imaging (3)
64 x 64 -gt 3200 px Res 10-7 arcsec -gt 1800
km Int. Time 15 min - 45 min
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Direct imaging (4)
128 x 128 -gt 12800 px Res 5.10-8 arcsec -gt 3600
km Int. Time 1h - 3h
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Direct imaging (5)
256 x 256 -gt51200 px Res 2.5 10-8 arcsec -gt
7200 km Int. Time 3.5 h - 10h
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Direct imaging (6)
512 x 512 -gt204800 px Res 1.2 10-8 arcsec -gt
15000 km Int. Time 14 h - 40h
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Direct imaging (7)
1024 x 1024 -gt825000 px Res 0.6 10-8 arcsec -gt
30000 km Int. Time 2.3 days - 7 days
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Direct imaging conclusion

• Observation of the surface
• OK at medium spatial resolution (200km/px)
• Observation of 10 km details
• about 1 week int time required (incl color
  information)
• OK for fixed objects towns, forests, seas,
• no hope to sea animals groups (except if they do
  not move)
• (Still) more difficult if the planet rotates or
  if dark side
• is observed (except if strong artificial light)
• -gt need to increase drastically the collecting
  area
• weightless mirrors, increase of the launch
• capabilities, complex formation flying required
• -gt reduction of the observation distance
• Observation probe

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Weightless mirrors

• Polymer mirrors
• Gaseous mirrors (Laser Trapped mirrors)

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3Nearer better ?
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A 10 pc trip ?

• Direct observation with a probe -gt nearby
  observation
• 10 pc trip
• Assuming c/10 (nuclear propulsion) about 300
  years to reach the target
• Single shot mission
• No  direct  data transmission -gt need to bring
  back the observation 300 years later.
• Self flying mission
• Strong risk of obsolescence

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4Do we contact them ?The role of SETI
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Conclusion

• DARWIN like missions are first but certainly
  most important steps providing strong clues for
  planetary composition and habitability
• Potential following missions should be HIGH
  RESOLUTION SPECTROSCOPY
• Direct imaging of the surface is difficult and
  maybe not relevant at low spatial resolution
• In situ exploration is a millennium project