Biosignatures Svetlana Berdyugina Kiepenheuer Institut fr Sonnenphysik Freiburg

Biosignatures Svetlana Berdyugina Kiepenheuer Institut für Sonnenphysik, Freiburg, Germany Hot Molecules in Exoplanets and Inner Disks

Content 1. Polarized biopigment absorption – – 2. Lab measurements Modeling Earth-like planets Exoplanet imaging – – Exo-Earths Proxima b

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)

Lab Measurements • Lab measurements: – reflection spectra – 400 -1000 nm – R~100 -200 – different angles – full Stokes vector • Samples: – vegetation – bacteria – sand/rocks – paper (Berdyugina et al. 2016, IJA Schwesinger & Berdyugina, in prep) /4 LP fiber sample iris

Chlorophyl (Berdyugina et al. 2016, IJA)

Carotenoids (Berdyugina et al. 2016, IJA)

Anthocyanins (Berdyugina et al. 2016, IJA)

Anthocyanins (Berdyugina et al. 2016, IJA)

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

Cyanobacterium

Microbacterium

Methylobacterium

Sands

Rocks

Planet Model • Earth atmosphere as basis (Stam 2008, modified): – transparent, optically thin gaseous atmosphere – optically thick H 2 O clouds – black ocean w. specular refl. – scattering & absorption – major bands of O 2, O 3, H 2 O – coverage fractions by plants, solids, and water – our lab reflection & polarization curves

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

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

80% Vegetation + 20% Clouds • Clouds gradually wash out flux signal need clear days! clouds 100%

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

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

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

Exo-Earth Models • Tatooine • Hoth

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 x orb y

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

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

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

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

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

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

SPHERE @ VLT • State-of-the-art PSF Langlois et al. 2014, SPIE

Telescopes to Detect ET Life • Proxima b: SPHERE best PSF, 1 h, A=0. 3, full illumination

Number of observable HZ exo-Earths

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

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>20 m are needed to see Proxima b and beyond.