Life in the Universe?

1. Life in the Universe? by R. T. F. Rekola Life in the Universe? Rami T. F. Rekola Tuorla Observatory University of Turku

2. Life in the Universe? by R. T. F. Rekola Life? • humans! • dogs! • lizards! • bacteria! • viruses? • androids?? • corpses??? • mules?!?!?! Fig: Funny Pictures Fig: Purdue University

3. Life in the Universe? by R. T. F. Rekola Definition of definition • linguistical approach (Oliver & Perry 2006, Origins of Life and Evolution of Biospheres, 34, 323-356) • OED: definition = a statement of the meaning of a word or the nature of a thing • unmistakable definitions are difficult, if not impossible

4. Life in the Universe? by R. T. F. Rekola • Oliver & Perry 2006: • theoretical definitions • stipulative definitions • operational definitions • a good definition: • necessary and sufficient • universal and apply to all past, present and future cases • essence of the term (by describing its function) • able to settle ambiguous cases

5. Life in the Universe? by R. T. F. Rekola • existing life definitions often describe living systems rather than life itself • some definitions are totally earth-centric ? Fig: Dickinson and Schaller

6. Life in the Universe? by R. T. F. Rekola • Prof. Koshland 2002 (Science, 295, 2215-2216): • ingredients and interactions among ingredients • ability to change / adapt to changes (mutation) • cells and organs • energy to recycle chemicals • ability to regenerate • individual adaptability to changes in environment • seclusion of chemical pathways

7. Life in the Universe? by R. T. F. Rekola • Ruiz-Mirazo et al. 2004: a complex collective network • Zhuravlev & Avetisov 2006: a combination of a state, a structure and a process • whatever definition you use, it is difficult to separate living and non-living things

8. Life in the Universe? by R. T. F. Rekola Prerequisites of life • chemical abundances Fig: New Holland Publishing

9. Life in the Universe? by R. T. F. Rekola • heavy elements Fig: ITER Fig: TheBest3D.com Fig: Stephen Mason

10. Life in the Universe? by R. T. F. Rekola • water Fig: IMAU

11. Life in the Universe? by R. T. F. Rekola Limits of survivability: from 0 Gy (?) to 15000 Gy • radiation Fig: Red Boiling Springs Florist

12. Life in the Universe? by R. T. F. Rekola • pressure Limits of survivability: from 0 atm to 1000 atm Fig: Panimpex

13. Life in the Universe? by R. T. F. Rekola Limits of survivability: from –250°C to +121°C (+150°C) Limits of livability: from –20°C to +121°C • temperature Fig: Richard Pelisson and Roland Pelisson, SaharaMet Fig: Her Majesty’s Armed Forces

14. Life in the Universe? by R. T. F. Rekola • salinity Limits of survivability: nearly saturated salts (e.g. rock salt) Fig: CSIRO

15. Life in the Universe? by R. T. F. Rekola • acidity Limits of survivability: pH 0 – 12 (0 – 13.7) Fig: webshots.net

16. Life in the Universe? by R. T. F. Rekola Habitable zones • water, organic molecules and amino acids are widespread in the universe • organic molecules in interstellar clouds • organic material in meteorites, comets and asteroids; and on planets and moons • distribution of heavy elements is quite universal

17. Life in the Universe? by R. T. F. Rekola • spectral type F and G, and possibly K and M type stars habitable

18. Life in the Universe? by R. T. F. Rekola Fig: Kasting et al. 1993, Icarus, 101, 108 • habitable zone is a distance range from the star – depending on radiation and where water stays liquid

19. Life in the Universe? by R. T. F. Rekola Galactic Habitable Zone • Gonzalez et al. 2001 (Icarus, 152, 185-200): metallicity at least half that of the Sun required to build a habitable terrestrial planet • bulge: old stars, continued star formation, high rate of supernovae in the past

20. Life in the Universe? by R. T. F. Rekola Fig: Swinburne University • thin disk: 360 pc thick, variety of stars and active star formation • GHZ, an annulus in the thin disk • innermost planets large, heavy iron cores, lots of radioactivity • outermost planets small, too little radioactive heating • annulus 4–18 kpc (or 7–9 kpc)

21. Life in the Universe? by R. T. F. Rekola • thick disk: 1.2 kpc thick, very old stars of low metallicity • halo: 100 kpc radius, oldest and metal-poorest stars • at least 10 million habitable planets in the Galaxy (von Bloh et al. 2002, in Lacoste H. ed., Proceedings of the First European Workshop on Exo-Astrobiology, pp. 503-504) Fig: universe-review.ca

22. Life in the Universe? by R. T. F. Rekola Habitable Zones in the Universe • galaxy evolution is not the same everywhere • galaxy types have differences • habitability of spheroidals poorly known • spiral galaxies likely to match the Milky Way

23. Life in the Universe? by R. T. F. Rekola • early universe had too much radiation • late universe will have too little to build on • habitable age of the universe began 5 Gyr ago and will continue for 10-20 Gyr more Fig: R. T. F. Rekola

24. Life in the Universe? by R. T. F. Rekola The Fermi Paradox “Where is everybody?” N = R × fp× ne× fl× fi× fc× L NS = 6000 NM = 22000

25. Life in the Universe? by R. T. F. Rekola • advanced civilisations • interstellar communication is not easy • life is rare or we are alone On the other hand... if N = 10000, average distances about 340 pc

26. Life in the Universe? by R. T. F. Rekola Conclusions • we need to know what is life • we need to find where it lives • we can then search for it • …and find it… Figs from left: - John Sarkissian - Arecibo Observatory - Brian Attebery - NASA