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Life in the Universe? Rami T. F. Rekola Tuorla Observatory University of Turku Life? humans! dogs! lizards! bacteria! viruses? androids?? corpses??? mules?!?!?! Fig: Funny Pictures Fig: Purdue University Definition of definition

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Life in the universe l.jpg

Life in the Universe? by R. T. F. Rekola

Life in the Universe?

Rami T. F. Rekola

Tuorla Observatory

University of Turku


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Life in the Universe? by R. T. F. Rekola

Life?

  • humans!

  • dogs!

  • lizards!

  • bacteria!

  • viruses?

  • androids??

  • corpses???

  • mules?!?!?!

Fig: Funny Pictures

Fig: Purdue University


Definition of definition l.jpg

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


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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


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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


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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


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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


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Life in the Universe? by R. T. F. Rekola

Prerequisites of life

  • chemical abundances

Fig: New Holland Publishing


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Life in the Universe? by R. T. F. Rekola

  • heavy elements

Fig: ITER

Fig: TheBest3D.com

Fig: Stephen Mason



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Life in the Universe? by R. T. F. Rekola

Limits of survivability:

from 0 Gy (?) to 15000 Gy

  • radiation

Fig: Red Boiling Springs Florist


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Life in the Universe? by R. T. F. Rekola

  • pressure

Limits of

survivability:

from 0 atm to

1000 atm

Fig: Panimpex


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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


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Life in the Universe? by R. T. F. Rekola

  • salinity

Limits of survivability:

nearly saturated salts (e.g. rock salt)

Fig: CSIRO


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Life in the Universe? by R. T. F. Rekola

  • acidity

Limits of survivability:

pH 0 – 12

(0 – 13.7)

Fig: webshots.net


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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


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Life in the Universe? by R. T. F. Rekola

  • spectral type F and G, and possibly K and M type stars habitable


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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


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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


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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)


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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


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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


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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


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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


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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


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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


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