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

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 d’Astrophysique Spatiale d’Orsay (2) IPAC - Caltech. DARWIN’s quest : first order spectroscopy.

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

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  1. 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 d’Astrophysique Spatiale d’Orsay (2) IPAC - Caltech

  2. DARWIN’s quest : first order spectroscopy …Pleurant, je voyais de l'or, - et ne pus boire. (A. Rimbaud) VIRA - 20/21/22 March 2006 - PARIS - MO

  3. 1What is the composition of the planetary atmosphere ?Is it primitive or did it evolve ?What about bio-markers ? VIRA - 20/21/22 March 2006 - PARIS - MO

  4. wavelength (mm) Resolution 10, 20, 10, 25 3, 20, 25 6 3, 20, 20 50 30 100 17 3, 3 4 4, 16, 19 4, 16, 19, 20, 20 20 10 6 5 NH3 SO2 CH4 N2O NO NO2 CO O3 H2O CO2 CO2 (50 mbar) CO2 (1 bar) Infrared spectral range Selsis, ESA SP 518, 2002 VIRA - 20/21/22 March 2006 - PARIS - MO

  5. Multi criteria spectral analysis • Requires low res. spectra (r=20-50), 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) VIRA - 20/21/22 March 2006 - PARIS - MO

  6. High resolution spectroscopy • Specific spectral features at (r=200-500) e.g : technological gases • Observation still at the planet scale • S/N depending on the features • Pb of contaminations by other species… VIRA - 20/21/22 March 2006 - PARIS - MO

  7. 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 -> ELT in space -> Improvement in the instrument performance -> classical imaging + coronagraph -> other concept ? VIRA - 20/21/22 March 2006 - PARIS - MO

  8. High resolution spectroscopy : how to ? • Angular résolution : 0.1 arcsec at 10 m -> 20-40 m class telescope • Collecting area compatible • High performance coronagraph • Global efficiency x 10 at least • No need for hyper telescope -> « BIG » NGST VIRA - 20/21/22 March 2006 - PARIS - MO

  9. 2What about the surface ?Are there evident traces of life activity on the planetary surface ?Can we image them ? VIRA - 20/21/22 March 2006 - PARIS - MO

  10. 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 -> 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 % VIRA - 20/21/22 March 2006 - PARIS - MO

  11. Direct imaging 16 x 16 -> 200 px Res = 4. 10-7 arcsec -> 450 km Int. Time ~ 1 min - 3min VIRA - 20/21/22 March 2006 - PARIS - MO

  12. Direct imaging (2) 32 x 32 -> 800 px Res = 2. 10-7 arcsec -> 900 km Int. Time ~ 3.5 min - 10 min VIRA - 20/21/22 March 2006 - PARIS - MO

  13. Direct imaging (3) 64 x 64 -> 3200 px Res = 10-7 arcsec -> 1800 km Int. Time ~ 15 min - 45 min VIRA - 20/21/22 March 2006 - PARIS - MO

  14. Direct imaging (4) 128 x 128 -> 12800 px Res = 5.10-8 arcsec -> 3600 km Int. Time ~ 1h - 3h VIRA - 20/21/22 March 2006 - PARIS - MO

  15. Direct imaging (5) 256 x 256 ->51200 px Res = 2.5 10-8 arcsec -> 7200 km Int. Time ~ 3.5 h - 10h VIRA - 20/21/22 March 2006 - PARIS - MO

  16. Direct imaging (6) 512 x 512 ->204800 px Res = 1.2 10-8 arcsec -> 15000 km Int. Time ~14 h - 40h VIRA - 20/21/22 March 2006 - PARIS - MO

  17. Direct imaging (7) 1024 x 1024 ->825000 px Res = 0.6 10-8 arcsec -> 30000 km Int. Time ~ 2.3 days - 7 days VIRA - 20/21/22 March 2006 - PARIS - MO

  18. 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)… • -> need to increase drastically the collecting area • weightless mirrors, increase of the launch • capabilities, complex formation flying required • -> reduction of the observation distance • Observation probe VIRA - 20/21/22 March 2006 - PARIS - MO

  19. Weightless mirrors • Polymer mirrors • Gaseous mirrors (Laser Trapped mirrors) VIRA - 20/21/22 March 2006 - PARIS - MO

  20. 3Nearer better ? VIRA - 20/21/22 March 2006 - PARIS - MO

  21. A 10 pc trip ? • Direct observation with a probe -> nearby observation • 10 pc trip • Assuming c/10 (nuclear propulsion): about 300 years to reach the target • Single shot mission • No « direct » data transmission -> need to bring back the observation 300 years later. • Self flying mission • Strong risk of obsolescence… VIRA - 20/21/22 March 2006 - PARIS - MO

  22. 4Do we contact them ?The role of SETI VIRA - 20/21/22 March 2006 - PARIS - MO

  23. 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 VIRA - 20/21/22 March 2006 - PARIS - MO

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