1. Detecting Photosynthesis on Exoplanets Orbiting M-Class Stars Sky Rashby Advisor: Yuk L. Yung

2. Detecting Extrasolar Life ESA Darwin / NASA TPF Interferometer operating from 6.5 to 18 microns Coronagraph operating from 600 to 1200 nanometers Spectral observations of distant (point-source) planets (nasa.gov; previous: www.rummet.dk) Potential for life Planetary characteristics - Orbital parameters Atmospheric properties - H 2 O - Chemical disequilibrium Photopigments??? TPF-C TPF-I

3. The Red Edge (Seager et al. 2005, adapted; Arnold et al. 2002, adapted)

4. Harvesting Light (Nelson & Cox 2000)

5. A Naturally Amplified Signal (Gates 1965, adapted)

6. Modeling Extrasolar Life Class M star –Long-lived –Abundant (~70%) Terrestrial –Exposure –Nutrient supply Oxygenic –Abundant electron source Structurally complex –Maximal energy harvesting Longer λ red edge –Adaptation to available solar flux –3-photon (Wolstencroft & Raven 2002) (McQuarrie 1985, adapted)

7. PROSPECT Optical model of plant leaves (Jacquemoud & Baret 1990) Uses plate model Modified pigment absorption properties Output: whole leaf spectrum shifted to longer wavelengths (jussieu.fr)

8. Cultivating the Exoplanet Modeling after Tinetti et al. (2005; refs. therein) LBLABC → absorption coefficients SMART radiative transfer model → single pixels Pixels averaged using Healpix (Liou 2002; Tinetti in press)

9. Edge Without H 2 O

10. With H 2 O

11. Compared to Grass

12. Disk Averaging

13. Realistic Clouds

14. Outlook Drier atmosphere → stronger signal Optimal detection without clouds High vegetation surface coverage required

15. Future Goals Use GCM data for M-star planet to: –Project planetary vegetation coverage –Estimate cloud distribution Use retrievals to estimate column amounts of water Add realistic viewing orientations Shorter λ edge with hotter star?

16. Acknowledgements & References Many thanks: Yuk Yung, Giovanna Tinetti References : Arnold, L., S. Gillet, et al. (2002). "A test for the search for life on extrasolar planets - Looking for the terrestrial vegetation signature in the Earthshine spectrum." Astronomy & Astrophysics 392(1): 231-237. Gates, D. M., H. J. Keegan, et al. (1965). "Spectral Properties Of Plants." Applied Optics 4(1): 11-&. Liou, K. N. (2002). An Introduction to Atmospheric Radiation. San Diego, Academic Press. McQuarrie, D. A. (1983). Quantum Chemistry. Suasalito, University Science Books. Nelson, D. L. and M. M. Cox (2000). Principles of Biochemistry. New York, Worth. Seager, S., E. L. Turner, et al. (2005). "Vegetation's red edge: A possible spectroscopic biosignature of extraterrestrial plants." Astrobiology 5(3): 372-390. Tinetti, G., V. S. Meadows, et al. (In press). Detectability of Planetary Characteristics in Disk-Averaged Spectra I: the Earth Model. Tinetti, G., V. S. Meadows, et al. (2005). "Disk-averaged synthetic spectra of Mars." Astrobiology 5(4): 461-482. Tinetti, G., V. S. Meadows, et al. (In press). Detectability of Planetary Characteristics in Disk-Averaged Spectra I: the Earth Model. Wolstencroft, R. D. and J. A. Raven (2002). "Photosynthesis: Likelihood of occurrence and possibility of detection on earth-like planets." Icarus 157(2): 535-548.

17. (http://home.hiwaay.net/~krcool/Astro/moon/earthshine/)

18. (Heath et al. 1999)

19. (Madigan et al. 2000)