Accretion and Collisional Evolution of Our Solar System David A. Kring
Accretion and Collisional Evolution of Our Solar System
David A. Kring
Lunar and Planetary Institute
Formation of Stars & Planetary Systems
Key environment:
Molecular Clouds
Key environmental component:
Molecular Cloud Cores
Molecular Clouds
Interstellar clouds of dust and gas
Temperatures ~ 10 K
At these cold temperatures, atoms combine to form molecules (hence, the name molecular cloud).
Over 70 molecules have been identified using spectroscopic techniques, including:
Molecular hydrogen H2 Hydrogen cyanide HCN
Water H2O Ammonia NH3 Formaldehyde CH2O Molecular Cloud Cores
Denser regions of dust and gas within molecular clouds
Temperatures ~ 10 to 100 K
Cores become gravitationally unstable and collapse
Dust and gas collapse into a rotating disk rather than a denser sphere, because the cloud core was rotating prior to collapse Hood and Kring (1996) Disk is generally called a protostellar nebula; in our case, the solar nebula Protosolar Neighborhood
Isotopes and stardust suggest the Solar System formed in a seething cauldron of interstellar debris with explosive out-bursts of novae, supernovae, and Wolf-Rayet stars.
Novae and Wolf-Rayet stars, for example, eject shells of dust and gas with speeds of 1000’s km/s. National Geographic (1986) Solar Nebula Processes 105 – 106 years Planetesimal Accretion 10 Myr Terrestrial Planet Accretion 100 Myr
National Geographic (1986) Kring Condensation and/or distillation in solar nebula to produce objects with high concentrations of refractory elements like Ca, Al, Ti, and Pt.
Also called refractory inclusions. Allende CV3
CAI Formation 4.5672 ± 0.0006 Ga (e.g., Amelin et al., 2002)
0 10 50 Time (Millions of Years) 0.1 to 1 mm spherules Kring High-temperature storms in solar nebula melt aggregates of dust, producing a rain of Kring molten silicate and metal droplets that solidify within ~1 hour. Semarkona Composed dominantly of olivine and pyroxene,
Mokoia although some have Ca,Al-rich compositions Chondrule Formation that mimic CAI. 0 – 4 Myr (e.g., Hutcheon et al., 1994; Amelin et al., 2002, 2004) 0 10 50 Time (Millions of Years) Allende CAI, chondrules, and Fe,Mg,Si-rich matrix accrete to produce primitive parent bodies.
Water and other volatiles were mobilized, altering material in some of these planetesimals. Kring Accretion & Aqueous Alteration of Carbonaceous Chondrite Parent Bodies 0 – 7 Myr (e.g., Hutcheon & Phinney, 1996; Brearley et al., 2001; Hua et al., 2002)
0 10 50 Time (Millions of Years) Chondrules, and much less CAI and Fe,Mg,Si-rich matrix, accrete to produce primitive parent bodies.
Sufficient heating (perhaps by 26Al) thermally meta- morphoses the material, causing recrystallization and chemical equilibrium.
Thermal Metamorphism of Kring Astronomy (2006) magazine. Ordinary Chondrite Parent Bodies Begins <5 Myr; ? ? extends for ~10 Myr (e.g., Gopel et al., 1989) 0 10 50 Time (Millions of Years) A large planetesimal, between the orbits of Mars and Jupiter, melts and differentiates.
Meteoritic remnants of this planetesimal include the HED meteorites, which have been tentatively linked to asteroid 4 Vesta.
Vesta Differentiates
2.4 ± 0.9 Myr Kring Astronomy (2006) magazine. (Lugmair & Shukolyukov, 1998)
0 10 50 Time (Millions of Years) Accretion of large terrestrial planets or proto-planets that might still be affected by a late collision or accretional veneer.
Mars Accretes ~14 Myr (Kleine et al., 2002)
Mars Core Formation ~2 or ~20 Myr (Kleine & Halliday, 2006)
Kring Astronomy (2006) magazine.
0 10 50 Time (Millions of Years) Accretion of large terrestrial planets or proto-planets that might still be affected by a late collision or accretional veneer.
Earth Accretes ≤33 Myr (e.g., Kleine et al., 2002) possibly ~10 - 15 Myr (e.g., Kleine & Halliday, 2006)
Kring Astronomy (2006) magazine.
0 10 50 Time (Millions of Years) Accretion of large terrestrial planets or proto-planets that might still be affected by a late collision or accretional veneer.
Moon-forming Impact ~50 Myr, although possibly as early as 30 Myr (e.g., Kleine & Halliday, 2006)
Kring Astronomy (2006) magazine.
0 10 50 Time (Millions of Years) Within 100 Myr: Nebular Processes Kring (2003) Planetesimal and Planetary Accretion Thermal Metamorphism and Differentiation Crust Formation (at least on Moon and Mars) Kring (2003)
65015,151 width = 2.1 mm Impact Melt Breccia Thin-section view, crossed nicols Nectarian and Early Imbrian Impact Basins
Impact Basin Diameter (km) Age (Ga)
Orientale 930 3.82 – 3.84 ? Schrodinger 320 Early Basins
± Imbriam Imbrium 1,200 3.85 0.01 Bailly 300 Sikorsky-Rittenhouse 310
Hertzprung 570 3.89 ± 0.009 Serenitatis 740 3.895 ± 0.017 Crisium 1,060 3.89 ? Humorum 820 Humboldtianum 700 Medeleev 330 implying NectarianBasins Korolev 440 ~70 to 90 million year Moscovienese 445 bombardment Mendel-Rydberg 630 Nectaris 860 3.89 – 3.91 ?
For comparison, Chicxulub’s diameter is ~180 km The Apollo Legacy–
The radiometric ages of rocks from the lunar highlands indicated the lunar crust had been thermally metamorphosed ~3.9 – 4.0 Ga. A large number of impact melts were also generated at the same time.
This effect was seen in the Ar-Ar system (Turner et al., 1973) and the U-Pb system (Tera et al., 1974). It was also preserved in the more easily reset Rb-Sr system. (Data summary, left, from Bogard, 1995.)
A severe period of bombardment was inferred: the lunar cataclysm hypothesis.
Inner Solar System Cataclysm Hypothesis
Testing the hypothesis:
Was there really an enhanced impact rate at 3.9-4.0 Ga? New analyses of Apollo samples New analyses of lunar meteorites New analyses of asteroid impact melts Analysis of ALH84001, from ancient crust of Mars Thus far, all data are consistent with hypothesis
What was the dominant source of impacting debris? Asteroids? Comets? Kuiper belt objects?
Astrobiological issues being investigated:
Did the impacting debris deliver significant water and biogenic elements?
How did the impacting debris affect environments suitable for pre-biotic chemistry and the early evolution of life? The chemical compositions of these meteorites indicate they come from non-Apollo sites. Duration of bombardment 20 to 200 Ma
Data support this model
Cratered Asteroids
Impact melt breccias (e.g., Kring et al., 1996)
Kring
Melt veins in crater floors (e.g., Kring et al., 1999) Kring Kring and Cohen (2002) Inner Lunar Solar System Cataclysm Cataclysm Kring and Cohen (2002) Geological Fingerprints of the Impactor Population
Size distribution of impact craters in ancient terrains were used to calculated the
Size distribution of the impacting objects
Indicated asteroids were the dominant source of debris
Strom, Malhotra, Ito, Yoshida, & Kring (Science 2005)
Strom and Sprague Apollo 16 Sample 60016,181
Ancient regolith breccia that entrains visible (dark- colored) clasts of impact melt.
The melts can be analyzed to determine the ages of impacts
Their siderophile contents can be used to identify the type of NEA impactors
The sample also contains microscopic fragments of impactor relics
False-color element map of Apollo 16 Joy et al. (2012) sample 60016.
The image was made using innovative micro-analytical mapping technique to mineralogically fingerprint projectile fragments within lunar samples.
The colors denote the distribution and concentration of different elements (white = aluminium, blue = silicon, green = magnesium, yellow = calcium, red = iron, pink = titanium, cyan = potassium). The field of view is ~7 × 9 mm.
An UMMF (tiny green particle) Before the Lunar Cataclysm
Ancient Surfaces
Young Surfaces After the Lunar Cataclysm
Ancient Surfaces
Young Surfaces Proximity of the Moon to Earth during the Hadean
LPI (Kring and Blackwell)
What types of biogenic elements were delivered? How was the composition of the atmosphere altered?
How did impacts affect microbial evolution? How did impacts affect complex life (e.g., at K/T boundary)?
What are the future impact hazards? Earth’s Water
Although the impact cataclysm was sufficiently large to resurface Earth and other terrestrial planets, it was not dominant source of water on Earth and Mars; it delivered too little material.
Water had been delivered during earlier accretion.
Yet, it still managed to deliver significant biogenic elements
For example: Delivery of Biogenic Elements Assuming, for example, average projectile compo- sitions comparable to enstatite chondrites:
3.4 x 1021 g S 20 9.4 x 10 g H2O 3.2 x 1020 g C (i.e., 160 times larger than the total land biomass today)
Delivered in 20 to 200 Ma or, alternatively, 500 to 600 Ma Kring’s Impact-Origin of Life Hypothesis (with emphasis on the word “hypothesis”) Hydrothermally-altered Impact Breccia
Chicxulub, Kring et al. (2004) Thermophillic Organisms in Hydrothermal Environment
Yellowstone Farmer (2000) Modeling indicates complex craters had active hydrothermal systems for 104 to several times 106 years on early Earth and Mars. Impact-generated Hydrothermal Systems
Systems are extensive (spanning entire diameter of each crater)
Systems are long-lived (hundred thousand to a few million years, depending on crater size)
Leading us to predict (e.g., Kring, 2000, 2004; Abramov and Kring, 2004): (i) Noachian terrains should have abundant hydrothermal minerals (ii) That the hydrothermal alteration will be associated with impact-cratered terrains; because impact cratering is far more abundant than volcanism during this period, most hydrothermal alteration is impact-derived (iii) And younger terrains should have much less hydrothermal minerals because impact rate dramatically decreased.
Prediction confirmed by Mars Express (Pouclet et al., Science, 2005) But we are still operating in a data poor environment…….
Nectarian and Early Imbrian Impact Basins
Impact Basin Diameter (km) Age (Ga)
Orientale 930 3.82 – 3.84 ? Schrodinger 320 Early Basins
± Imbriam Imbrium 1,200 3.85 0.01 Bailly 300 Sikorsky-Rittenhouse 310
Hertzprung 570 3.89 ± 0.009 Serenitatis 740 3.895 ± 0.017 Crisium 1,060 3.89 ? Humorum 820 Humboldtianum 700 Medeleev 330 NectarianBasins Korolev 440 Moscovienese 445 Mendel-Rydberg 630 Nectaris 860 3.89 – 3.91 ?
For comparison, Chicxulub’s diameter is ~180 km Pre-Nectarian Basins
Impact Basin Diameter (km) Age (Ga)
Apollo 505 Grimaldi 430 Freundlick-Sharonov 600 Birkhoff 330 Planck 325 Schiller-Zucchius 325 Amundsen-Ganswindt 355 Lorentz 360 Smythii 840 Coulomb-Sarton 530 Keeler-Heaviside 780 Poincare 340 Ingenii 560 Lomonosov-Fleming 620 Nubium 690 Mutus-Vlacq 690 ? Tranquillitatis 800 Australe 880 Fecunditatis 990 Al-Khwarizmi/King 590 Pingre-Hausen 300 Werner-Airy 500 Balmer-Kapteyn 550 Flamsteed-Billy 570 Marginis 580 Insularum 600 Grissom-White 600 Tsiolkovskiy-Stark 700 South Pole-Aitken 2500 Procellarum 3200 Representative Eratothenian Craters
Impact Crater Diameter (km) Age (Ga)
Lambert 30 Reiner 30 Archytas 32 Timocharis 34 Stearns 37 Manilius 39 Herschel 41 Rothmann 42 Plinius 43 Reinhold 43 Agrippa 44 Hainzel A 53 ? Maunder 55 Eratosthenes 58 Bullialdus 61 Hercules 69 Werner 70 Fabricius 78 Aristoteles 87 Theophilus 100 (rayed) Pythagoras 130 Langrenus 132 (rayed) Hausen 167 (largest young crater) Representative Copernican Craters
Impact Crater Diameter (km) Age (Ga) Kepler 32 Petavius B 33 Godin 35 Autolycus 39 (ray at A15 site?) 1.29 Aristarchus 40 Olbers A 43 Crookes 49 Anaxagoras 51 Aristillus 55 (ray at A15 site?) 1.29 Taruntius 56 Eudoxus 67 King 77 Tycho 85 (landslide at A17 site?) 0.1 Copernicus 93 (ray at A12 site) 0.8-0.9
The age of only a single impact event, Tycho, is known during the Phanerozoic of Earth, which is the period of complex life on our planet. One cannot determine an impact rate with only a single data point. Were there pulses of activity at, say, 800 and 500 Ma? David A. Kring
Human-assisted sample return mission
• In 2021, NASA will fly crew around the Moon in the Orion vehicle.
• In subsequent missions, a robotic rover on the surface could collect samples and launch them into orbit, where astronauts could retrieve them for return to Earth.
LPI (Kring)
Burns, Kring, Norris, Hopkins, Lazio, & Kasper (2013) Sampling Ancient Mars (SAM)
Early solar system bombardment, which created impact-cratered highlands on Mars, ejected ancient crustal and potentially mantle components from Mars.
Calculations suggest 2 to 10% of the regolith of Diemos is composed of these ancient Mars samples.
Albedo measurements of Diemos confirm a bright component occurs in regolith that is consistent with Mars material.
SAM can collect ~2 kg of Diemos regolith, which will contain 40 g to perhaps 200 g of Mars samples. Thank you.