PanspermiaPanspermia

The Search for your The Search for your mothers mothermothers mother

OverviewOverview

Panspermia- Origin of Earth’s life from elsewherePanspermia- Origin of Earth’s life from elsewhere InterplanetaryInterplanetary InterstellarInterstellar

Asking the right questions: no answers in this Asking the right questions: no answers in this presentationpresentation Probability of life starting on Earth Vs. on another planetProbability of life starting on Earth Vs. on another planet

Enough time for life to evolve on earth?Enough time for life to evolve on earth? Getting that life hereGetting that life here

EjectionEjection transport: radiation, vacuum, travel time, cold temperaturetransport: radiation, vacuum, travel time, cold temperature entryentry

Panspermia Vs. Terrestrial Panspermia Vs. Terrestrial origins of life origins of life

Earth’s accretion, core formation, and Earth’s accretion, core formation, and degassing complete 4.47 Ga (Halliday)degassing complete 4.47 Ga (Halliday)

End of Intense bombardment 3.9 Ga End of Intense bombardment 3.9 Ga (Halliday)(Halliday)

Earliest life 3.5 Ga, 3.8 Ga? (Hayes) Earliest life 3.5 Ga, 3.8 Ga? (Hayes) 3.85-4.25 Ga? (Mojzsis)3.85-4.25 Ga? (Mojzsis)

Was there enough time for life to Was there enough time for life to evolve or was the earth seeded?evolve or was the earth seeded?

Are we alone? Other life in our Are we alone? Other life in our Solar System?Solar System?

VenusVenus MarsMars EuropaEuropa TitanTitan More likely on those planets?More likely on those planets?

Life originating on Mars Vs Life originating on Mars Vs EarthEarth

Early mars:Early mars: Ozone (pavlov et al., 2001)Ozone (pavlov et al., 2001) OxygenOxygen Magnetic Field providing protection (Acuna et al., 1999)Magnetic Field providing protection (Acuna et al., 1999)

Early Earth:Early Earth: No Ozone (pavlov)No Ozone (pavlov) No oxygenNo oxygen

Early Mars compared to early earth better place Early Mars compared to early earth better place for origin of life (Kirschvink, 2002)for origin of life (Kirschvink, 2002)

Are we alone? Life elsewhere Are we alone? Life elsewhere in the Universein the Universe

Earth like planets PFREarth like planets PFR Stellar Systems with Stellar Systems with

habitable planets in habitable planets in the milky waythe milky way GSM model (dashed)GSM model (dashed) GDM model (solid)GDM model (solid)

(Bloh, 2002)(Bloh, 2002) More time for evolution More time for evolution

of life to occurof life to occur 6 Ga6 Ga

Types of PanspermiaTypes of Panspermia

Lithopanspermia-within stoneLithopanspermia-within stone Radiopanspermia-single spermia Radiopanspermia-single spermia

across spaceacross space Directed Panspermia (Directed Panspermia (AliensAliens))

Difficulties of PanspermiaDifficulties of Panspermia

Escape from seed planetEscape from seed planet Interplanetary/stellar travelInterplanetary/stellar travel

RadiationRadiation VacuumVacuum Extreme temperaturesExtreme temperatures

Entry to seeded planetEntry to seeded planet

Survivability of ejection and Survivability of ejection and entryentry

Temperature: ALH48001 increased Temperature: ALH48001 increased temperature by only up to 40 degrees temperature by only up to 40 degrees Celsius during ejection and entry (Weiss et Celsius during ejection and entry (Weiss et al., 2000)al., 2000)

Accelerations of 4.27x10^6 m/s^2 10% Accelerations of 4.27x10^6 m/s^2 10% survival rate (Mastrapa et al., 2000)survival rate (Mastrapa et al., 2000) Mars 3x10^6Mars 3x10^6 Difficulty accelerating small particlesDifficulty accelerating small particles

Shocks of 32 GPa 1 in 10^4 survive Shocks of 32 GPa 1 in 10^4 survive (Horneck et al., 2001)(Horneck et al., 2001) Mars 20-45 GpaMars 20-45 Gpa

Length of time surviving in Length of time surviving in spacespace

Radiation: Need shieldingRadiation: Need shielding For 10% chance of survival:For 10% chance of survival:

0.1 myr-40 myr depending on shield thickness 0.1 myr-40 myr depending on shield thickness (Mileikowsky et al., 2000)(Mileikowsky et al., 2000)

1 myr (Parson, 1996)1 myr (Parson, 1996) 45 myr (Weber and Greenberg, 1985)45 myr (Weber and Greenberg, 1985) 250 myr (Vreeland et al., 2000)250 myr (Vreeland et al., 2000)

ALH48001 transport timeALH48001 transport time 10,000 to 100 mya transport time via heliocentric orbit10,000 to 100 mya transport time via heliocentric orbit Possibility of 1 year transport time 1x10^-7 (Burchell, Possibility of 1 year transport time 1x10^-7 (Burchell,

2003)2003)

(Bloh, 2003)

With square of distance impacts become less likely

Likelihood of Interstellar Likelihood of Interstellar panspermiapanspermia

““It is very unlikely that even a single meteorite It is very unlikely that even a single meteorite originating on a terrestrial planet in our solar originating on a terrestrial planet in our solar system has [ever] fallen onto a terrestrial system has [ever] fallen onto a terrestrial planet in another stellar system.” (Melosh, planet in another stellar system.” (Melosh, 2003)2003)

Only 1-2 meteorites captured by another solar Only 1-2 meteorites captured by another solar system post heavy bombardment system post heavy bombardment

1 in 10 k chance of captured meteorite 1 in 10 k chance of captured meteorite actually strikes a terrestrial planet (Melosh, actually strikes a terrestrial planet (Melosh, 2003) 2003)

Too long transport time for life to survive?Too long transport time for life to survive?

SummarySummary

Solar system’s planets more likely Solar system’s planets more likely than earth to have harbored life?than earth to have harbored life?

Interstellar planets much farther Interstellar planets much farther awayaway Less likely for panspermia event to Less likely for panspermia event to

occuroccur More likely for life to have evolvedMore likely for life to have evolved

Is the (improbable?) traveling from Is the (improbable?) traveling from another planet more likely to have another planet more likely to have occurred than life evolving on earth?occurred than life evolving on earth?

Direct SeedingDirect Seeding

BibliographyBibliography BibliographyBibliography

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