Amaya Moro-Martín Centro de Astrobiología (INTA-CSIC) & Princeton Univ.

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Amaya Moro-Martín Centro de Astrobiología (INTA-CSIC) & Princeton Univ. Chaotic exchange of solid material between planetary systems: implications for lithopanspermia Collaborators: Edward Belbruno (Princeton Univ.), Renu Malhotra (Univ. of Arizona), Dmitry Savransky (Princeton Univ. and Lawrence Livermore National Laboratory) Published in Belbruno, Moro-Martín, Malhotra, Savransky (Astrobiology 2012)

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Published in Belbruno, Moro-Martín, Malhotra, Savransky (Astrobiology 2012). Chaotic exchange of solid material between planetary systems: implications for lithopanspermia. Amaya Moro-Martín Centro de Astrobiología (INTA-CSIC) & Princeton Univ. - PowerPoint PPT Presentation

Transcript of Amaya Moro-Martín Centro de Astrobiología (INTA-CSIC) & Princeton Univ.

Amaya Moro-MartínCentro de Astrobiología (INTA-CSIC) & Princeton Univ.

Chaotic exchange of solid material between planetary

systems: implications for lithopanspermia

Collaborators: Edward Belbruno (Princeton Univ.), Renu Malhotra (Univ. of Arizona), Dmitry Savransky (Princeton Univ. and Lawrence Livermore National Laboratory)

Published in Belbruno, Moro-Martín, Malhotra, Savransky (Astrobiology 2012)

Approx. 20% of stars harbor giant planets < 20

AU

Giant planets are common

How common are they?

- Also present around white dwarfs (Jura et al. 2006, 2007)

- A (26%), F (24%), G (19%), K (9.5%), M (1.3%) (Kennedy in prep.)

Planetesimal disks are common

0.01-1 Myr 10 Myr-10,000 Myrdust lifetime << stellar age

The dust is not primordial but it must be

generated by planetesimals

Planetesimal formation takes

places under a wide range of

conditions

•But there is evidence of dust around older stars (debris

disks).

•Protoplanetary disks of gas and dust (100:1 mass ratio)

are present around most stars; they dissipate in ~ 6 Myr.

(Jewitt 2010)

Solar System debris

disk

extra-solar debris disk

β-Pictoris(Schultz, HST)

(Raymond, Armitage, Moro-Martin et al. 2011)

Giant planets eject planetesimals efficiently

Is the exchange of solid material

possible between planetary systems?

The interstellar medium must be filled with

planetesimals

• Giant planets are common

• Planetesimal disks are common

• Giant planets eject planetesimals

efficiently

Transfer of solid material between single stars in an open star cluster

Solar System properties that depend on birth environment: - evidence of short-lived radionuclides in meteorites - dynamical properties of outer planets and Kuiper Belt

The Sun was born in an open star cluster

- Number of stars: N = 4300 (N=1000-10000)

- Cluster mass: M = <mstar> N = 3784 Msun

- Cluster size: R ~1pc (N/300)0.5 = 3.78 pc

- Average stellar distance: D = n-1/3 = 0.375 pc

- Cluster lifetime: t = 2.3Myr M0.6 = 322.5 Myr

(135-535 Myr for N=1000-10000)

(similar to Orion’s Trapezium)

Cluster properties (Adams 2010)

Weak transfer using quasi-parabolic orbits

-Region where the particle is tenuously and

temporarily captured.

-Created by the gravitational fields of the central

star, the giant planet and the rest stars in the

cluster.

-The particle slowly meanders between both

planetary systems.

•The transfer takes place between two

weak stability boundaries: planetar

y fragme

nt

weak stability boundary for

capture (σ = 1 km/s)

weak stability boundary for

escape (σ = 0.1 km/s)

•Stars relative velocity ~ 1 km/s (determining capture velocity)

(relative velocity between

stars)

stargiant planet

giant plane

t

planetary system of destination

planetary system of origin

star

•Assume both planetary systems harbor a

Jupiter-like planet

(ejection velocity)•Typical ejection velocity ~ 0.1 km/s

•Minimum energy; maximizes transfer

probability

(Belbruno, Moro-Martín, Malhotra, Savransky, 2012)

Monte Carlo simulations

Monte Carlo simulations

(Belbruno, Moro-Martín, Malhotra, Savransky, 2012)

M* source (Msun) M* target (Msun) Capture probab.

1.0 1.0 0.15%

1.0 0.5 0.05%

0.5 1.0 0.12%

Weak capture probabilities

•Melosh (2003):

- transfer between single stars in the solar local neighborhood (after cluster

dispersal)

(ours: before cluster disperses)

- stars velocitiy dispersion: 20 km/s (ours: 1 km/s)

- hyperbolic trajectories with median ejection speed of 5 km/s (ours: 0.1 km/s)

- capture probability ~109 times smaller than with weak transfer

•Adams & Spergel (2005)

- transfer between binary stars in an open cluster (ours: single stars like the Sun)

- hyperbolic trajectories with median ejection speed of 5 km/s (ours: 0.1 km/s)

- capture probability ~103 times smaller than with weak transfer

Comparison to previous work

(between the Sun and its closest cluster neighbor)

Number of weak transfer events

(from KBO observations and coagulation models)

Dmax = 2000 km (Pluto) Dmin = 1 μm (blow-out size)

dN/dD ∝ D−q1 for D > D0

dN/dD ∝ D−q2 for D < D0

Adopt a planetesimal size distribution

(adopting a MMSN)

Number of bodies > 10

kg

(using an Oort Cloud formation efficiency of 1%, Brasser et al. 2012).

Number of bodies >10 kg

that populated the

WSB

(using a capture probability of 0.15%)

Number of bodies >10 kg

may have been

transferred

Number of weak transfer events: O(1014)-O(1016)

Timeline

window of opportunity of lithopanspermia from Earth

Birth cluster lifetime, dispersed over approx. 135–535 million years

star cluster135 Myr

535 Myr

(Adams 2010)

322 Myr

Moon formation

44 Myr

Cooling of Earth’s crust

70 Myr

1st microfossils

1170 Myr

t = 0

solar system (CAI)

formation

718 Myr

Earth

(4.57 Ga)

(Kleine et al. 2005)

(Mojzsis et al. 1996)

(Wacey et al. 2011)(Harrison et al. 2005) (Schopf, 1993)

(shortly after end end of LHB)

Evidence of liquid water on Earth’s

surface

164 288Myr Myr

(Wilde et al. 2001).

(Mojzsis et al. 2001)

1st evidence of microbiological

activity

solar system 700

Myr

end of LHB

Heavy bombardment; planetesimal clearing; population of the sun’s WSB

with planetary fragments

Assuming l (km) of the Earth surface was ejected, this correspond to a mass of...

adopting a power-law size distribution,

the number of bodies > 10 kg is

~ 1% remained weakly shocked (allowing microorganisms to survive) ~

How much material may have been ejected from Earth?

~ 1% populated the Oort Cloud (WSB of the Solar System) ~

5‧105 ‧ l(km)

~ 0.15% may have been transferred to the nearest solar-type stars ~

Time for ejection

4 Myr min. 50 Myr median.6 Myr time of flight to Resc

Time for transfer

5 Myr (at 0.1 km/s)Time for capture by terrestrial planet10’s Myr

Comparison between transfer and life survival timescales

Size Max. survival time

0-0.03 m 12-15 Myr

0.03-0.67 m 15-40 Myr

0.67-1 m 40-70 Myr

1-1.67 m 70-200 Myr

1.67-2 m 200-300 Myr

2-2.33 m 300-400 Myr

2.33-2.67 400-500 MyrValtonen et al. (2009)

Survival of microorganisms could be viable via meteorites exceeding 1m in size

In a nutshell

•We use chaotic, quasi-parabolic orbits of minimal energy that increase greatly the transfer probability.

•We study the transfer of meteoroids between two planetary systems embedded in an open star cluster.

Orion’s Trapezium cluster (2.2 μm)

•We find that significant quantities of solid material are exchanged.

•If life on Earth had an early start (arising shortly after liquid water was available on the surface), life could have been transferred to other systems.

•And vice versa, if life had a sufficiently early start in other planetary systems, it could have seeded the Earth (and may have survived the LHB).