Panspermia

1. Panspermia The Search for your mothers mother

2. Overview • Panspermia- Origin of Earth’s life from elsewhere • Interplanetary • Interstellar • Asking the right questions: no answers in this presentation • Probability of life starting on Earth Vs. on another planet • Enough time for life to evolve on earth? • Getting that life here • Ejection • transport: radiation, vacuum, travel time, cold temperature • entry

3. Panspermia Vs. Terrestrial origins of life • Earth’s accretion, core formation, and degassing complete 4.47 Ga (Halliday) • End of Intense bombardment 3.9 Ga (Halliday) • Earliest life 3.5 Ga, 3.8 Ga? (Hayes) 3.85-4.25 Ga? (Mojzsis) • Was there enough time for life to evolve or was the earth seeded?

4. Are we alone? Other life in our Solar System? • Venus • Mars • Europa • Titan • More likely on those planets?

5. Life originating on Mars Vs Earth • Early mars: • Ozone (pavlov et al., 2001) • Oxygen • Magnetic Field providing protection (Acuna et al., 1999) • Early Earth: • No Ozone (pavlov) • No oxygen • Early Mars compared to early earth better place for origin of life (Kirschvink, 2002)

6. Are we alone? Life elsewhere in the Universe • Earth like planets PFR • Stellar Systems with habitable planets in the milky way • GSM model (dashed) • GDM model (solid) (Bloh, 2002) • More time for evolution of life to occur • 6 Ga

7. Types of Panspermia • Lithopanspermia-within stone • Radiopanspermia-single spermia across space • Directed Panspermia (Aliens)

8. Difficulties of Panspermia • Escape from seed planet • Interplanetary/stellar travel • Radiation • Vacuum • Extreme temperatures • Entry to seeded planet

9. Survivability of ejection and entry • Temperature: ALH48001 increased temperature by only up to 40 degrees Celsius during ejection and entry (Weiss et al., 2000) • Accelerations of 4.27x10^6 m/s^2 10% survival rate (Mastrapa et al., 2000) • Mars 3x10^6 • Difficulty accelerating small particles • Shocks of 32 GPa 1 in 10^4 survive (Horneck et al., 2001) • Mars 20-45 Gpa

10. Length of time surviving in space • Radiation: Need shielding • For 10% chance of survival: • 0.1 myr-40 myr depending on shield thickness (Mileikowsky et al., 2000) • 1 myr (Parson, 1996) • 45 myr (Weber and Greenberg, 1985) • 250 myr (Vreeland et al., 2000) • ALH48001 transport time • 10,000 to 100 mya transport time via heliocentric orbit • Possibility of 1 year transport time 1x10^-7 (Burchell, 2003)

11. With square of distance impacts become less likely (Bloh, 2003)

12. Likelihood of Interstellar panspermia • “It is very unlikely that even a single meteorite originating on a terrestrial planet in our solar system has [ever] fallen onto a terrestrial planet in another stellar system.” (Melosh, 2003) • Only 1-2 meteorites captured by another solar system post heavy bombardment • 1 in 10 k chance of captured meteorite actually strikes a terrestrial planet (Melosh, 2003) • Too long transport time for life to survive?

13. Summary • Solar system’s planets more likely than earth to have harbored life? • Interstellar planets much farther away • Less likely for panspermia event to occur • More likely for life to have evolved • Is the (improbable?) traveling from another planet more likely to have occurred than life evolving on earth?

14. Direct Seeding

15. Bibliography • Bibliography • Acuna M., Connerney J., Ness N., Lin R., Mitchell D., Carlson C.l, McRadden J., Anderson K., Reme H., Maselle C., Vignes D., Wasilewski P., and Cloutier P. (1999) Global distribution of crustal magnetization discovered by the mars global surveyor MAG/ER experiment. Science, 284, 790-793. • Bloh W. V., Franck S., Bounama C., and Schellnhuber H. (2003) Maximum Number of Habitable Planets at the Time of Earth’s Origin: New Hints for Panspermia? Origins of life and Evolution of the Biosphere, 33, 219-231. • Burchell M. J., Galloway J. A., Bunch A. W., Brandao P. F. B. (2003) Survivability of Bacteria Ejected from Icy Surfaces after Hypervelocity Impact. Origins of life and Evolution of the Biosphere, 33, 53-74. • Greeney R. Personal communication. December 2006. Note: 10-100k estimate is based on size of milky way galaxy and number of stars, assuming equal distribution in a disk. • Halliday A. (2001) In the beginning… Nature, 409, 144-145. • Hayes J. (1996) The earliest memories of life on Earth. Nature, 384, 21-22 • Kirschvink J. L. and Weis B. P. (2002) Mars, Panspermia, and the Origin of Life: Where did it all begin? Palaeontologia Electronica, 4, 2, 8-15 • Mastrapa, R. M. E., Glanzber J., Jead J.N., Melosh H. J., and Nicholson W. L. (2001) Survival of bacteria exposed to extreme acceleration: Implications for panspermia. Earth and Planetary Science Letters, 189: 1-8. • Melosh H. J. (2003) Exchange of Meteorites (and life?) Between Stellar Systems. Astrobiology, 3, 1,207-215. • Mojzsis S. J., Arrhenius G., McKeegan K. D., Harrison T. M., Nutman A. P., and Friends C. R. L. (1996) Evidence for life on Earth before 3,800 million years ago. Nature, 384, 55-56. • Pavlov A. A., Brown L. L., and Kastings J. F. (2001) UV shielding of NH3 and O2 by organic hazes in the Archean atmosphere. Journal of Geophysical Research, 106: 23267-23287. • Weiss B. P., Vali H., Baudenbacher F. J., and Widswo J. P. (2000) A low temperature transfer of ALH84001 from Mars to Earth. Science, 290, 791-795.