1. Biosignatures Svetlana Berdyugina
Kiepenheuer Institut für Sonnenphysik,
Freiburg, Germany
SPW3, Tenerife, 2002
Hot Molecules in Exoplanets and Inner Disks

2. Content Polarized biopigment absorption Exoplanet imaging
Lab measurements
Modeling Earth-like planets
Exoplanet imaging
Exo-Earths
Proxima b
SPW3, Tenerife, 2002

3. Polarized Biopigments
Photosynthesis is the interaction of life with stellar light
produces conspicuous biosignatures in polarized light (broadly used in botanic and agriculture for remote sensing of crops)
source of energy for nearly all life on Earth (captures 130 TW)
very likely to emerge early and last long on another planet
Common photosynthetic bio-molecules (pigments) in plants, algae, bacteria:
Chlorophyl (green)
Carotenoids (yellow/orange)
Anthocyanins (red/purple)
Phycobilin (blue)

4. Lab Measurements Lab measurements: reflection spectra 400-1000 nm
(Berdyugina et al. 2016, IJA
Schwesinger & Berdyugina, in prep)
Lab measurements:
reflection spectra nm R~
different angles
full Stokes vector
Samples:
vegetation
bacteria
sand/rocks
paper
sample
iris
/4 LP
fiber

5. Chlorophyl
(Berdyugina et al. 2016, IJA)

6. Carotenoids
(Berdyugina et al. 2016, IJA)

7. Anthocyanins
(Berdyugina et al. 2016, IJA)

8. Anthocyanins
(Berdyugina et al. 2016, IJA)

9. Photosynthetic Bacteria
Bio-aerosols in the Earth’s atmosphere
25% of total airborne particles larger than 0.2 μm
Biosphere signature
Bio-pigment functions
store energy
protect from UV radiation
Samples
collected from atmosphere
grown in the lab
Polarimetric measurements
wet & dry samples
reflection & transmission
Stokes IQUV

10. Cyanobacterium

11. Microbacterium

12. Methylobacterium

13. Sands

14. Rocks

15. Planet Model Earth atmosphere as basis (Stam 2008, modified):
transparent, optically thin gaseous atmosphere
optically thick H2O clouds
black ocean w. specular refl.
scattering & absorption
major bands of O2, O3, H2O
coverage fractions by plants, solids, and water
our lab reflection & polarization curves

16. Earths with 100% Vegetation
(Berdyugina et al. 2016, IJA)
Bio-molecules are distinguished best in polarized light!

17. Earths with 100% Sand & Rocks
Sandy and Vegi Earths differ in polarized light (exc red?)

18. 80% Vegetation + 20% Clouds
Clouds gradually wash out flux signal  need clear days!
clouds100%

19. 80% Vegetation + 20% Ocean
Black ocean with specular reflection preserves bio-signals
clear ocean 100%

20. BRDF
(Schwesinger & Berdyugina, in prep.)
Intensity:
Polarization:

21. Alderaan Tatooine Hoth Endor Exo-Earth Models Model:
Multiple scat./reflect.
Var. opt. thickness
Surface structures
Clouds
Snow
Ocean
Vegetation/bacteria
Sand
(Schwesinger & Berdyugina, in prep)
Alderaan
Tatooine
Hoth
Endor

22. Exo-Earth Models
Tatooine
Hoth

23. Exoplanet Reflected Light
Inversion Algorithm
Occam.Appr. (Berdyugina 1998)
Parameters:
Orbit normal inclination: iorb
Orbit normal azimuth: orb
Planet axis inclination: irot
Orbital period : Porb
Planet rotation period: : Prot
Result:
Planet albedo map: A(lat,long)
Inversion quality: IQ, SD, 2 (simul. data)
Parameter errors
(Berdyugina & Kuhn, in prep) z
iorb y
orb x

24. Exo-Earth Reflected Light Simulations
NASA Earth Observations (NEO) database: Albedo maps (2003/03)
Exo-Earth Light Curve
(Berdyugina & Kuhn, in prep)

25. Exo-Earth Inversion
6x6 North up irot=60, iorb=30, orb=60 (Npix=1800) Porb = 60Prot (Mdata=3000) S/N=200 IQ=89%, SD=10%
(Berdyugina & Kuhn, in prep)

26. Exo-Earth Inversion
6x6 South up irot=60, iorb=30, orb=60 (Npix=1800) Porb = 60Prot (Mdata=3000) S/N=200 IQ=89%, SD=15%
(Berdyugina & Kuhn, in prep)

27. Proxima b: Tidally locked
6x6 North up irot=60, iorb=30, orb=60 (Npix=1800) Porb = Prot , Norb=20 (Mdata= 600) S/N=100 IQ=84%, SD=13%

28. Proxima b: 3:2 resonance locked
6x6 North up irot=60, iorb=30, orb=60 (Npix=1800) 2Porb = 3Prot , Norb=20 (Mdata= 600) S/N=100 IQ=87%, SD=12%

29. Proxima b: Parameter Retrieval
6x6 North up irot=60, iorb=30, orb=60 (Npix=1800) Porb = Prot , Norb=20 (Mdata= 600) S/N=100

30. VLT
State-of-the-art PSF
Langlois et al. 2014, SPIE

31. Telescopes to Detect ET Life
Proxima b: SPHERE best PSF, 1h, A=0.3, full illumination

32. Number of observable HZ exo-Earths

33. Exo-Life Finder
20m-class interferometric telescope for high-contrast imaging of exoplanets will provide first surface images of Proxima b

34. Conclusions
Biopigment polarization is a sensitive bio-marker to detect life on other planets
characteristic spectral signatures,
polarization is much more sensitive than flux spectra detection
Indirect imaging (mapping) of exoplanets is possible with next generation large telescopes
Telescopes with D>20m are needed to see Proxima b and beyond.