Jupiter's Influence on the Building Blocks of Mars and Earth

Matsumura

et al. 2018

A&A

Dynamical models of planet formation coupled with cosmochemical data from martian meteorites show that Mars’ isotopic composition is distinct from that of Earth. Reconciliation of formation models with meteorite data require that Mars grew further from the Sun than its present position. Here, we evaluate this compositional difference in more detail by comparing output from two N-body planet formation models. The first of these planet formation models simulates what is termed the “Classical” case wherein Jupiter and Saturn are kept in their current orbits. We compare these results with another model based on the “Grand Tack”, in which Jupiter and Saturn migrate through the primordial asteroid belt. Our estimate of the average fraction of chondrite assembled into Earth and Mars assumes that the initial solid disk consists of only sources of enstatite chondrite composition in the inner region, and ordinary chondrite in the outer region. Results of these analyses show that both models tend to yield Earth and Mars analogues whose accretion zones overlap. The Classical case fares better in forming Mars with its documented composition (29–68% enstatite chondrite plus 32–67% ordinary chondrite) though the Mars analogues are generally too massive. However, if we include the restriction of mass on the Mars analogues, the Classical model does not work better. We also further calculate the isotopic composition of 17O, 50Ti, 54Cr, 142Nd, 64Ni, and 92Mo in the martian mantle from the Grand Tack simulations. We find that it is possible to match the calculated isotopic composition of all the above elements in Mars’ mantle with their measured values, but the resulting uncertainties are too large to place good restriction on the early dynamical evolution and birth place of Mars.

Section: Bulk Compositional Differences Between Earth and Marssupporting

confidence: 88%

Section: Chondrite Fractions To Make Earth and Marsmentioning

confidence: 64%

The curious case of Mars’ formation

Woo

Matsumura

et al. 2018

A&A

“…All of these models can reproduce the mass-orbital distance relation of the terrestrial planets and their orbital excitation with various degrees of success. When tied to the documented compositions of the sampled Solar System (Earth, Moon, Mars and asteroids), some are also deemed better than others at reproducing the isotopic composition of the terrestrial planets (Brasser et al, , 2018Woo et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Impact bombardment chronology of the terrestrial planets from 4.5 Ga to 3.5 Ga

Werner

Mojzsis

2020

Icarus

Self Cite

Subsequent to the Moon's formation, late accretion to the terrestrial planets strongly modified the physical and chemical nature of their silicate crusts and mantles. Here, we combine dynamical N-body and Monte Carlo simulations to determine impact probabilities, impact velocities, and expected mass augmentation onto the terrestrial planets from three sources: planetesimals left over from primary accretion, asteroids from the hypothetical E-belt, and comets arriving from the outer Solar System. We present new estimates of the amount of cometary material striking the terrestrial planets in an early (ca. 4480 Ma) episode of planetesimal-driven giant planet migration . We conclude that the Moon and Mars suffer proportionally higher cometary accretion than Venus and Earth. We further conclude that the background mass addition from small leftover planetesimals to Earth and Mars is far less than independent estimates based on their respective mantle abundances of highly-siderophile elements and terrestrial tungsten isotopes. This supports the theory that both planets were struck by single large bodies that delivered most of their terminal mass augmentation since primary accretion, rather than a throng of smaller impactors. Our calculated lunar, martian and mercurian chronologies use the impacts recorded onto the planets from dynamical simulations rather than relying on the decline of the population as a whole. We present fits to the impact chronologies valid from 4500 Ma to ca. 3700 Ma by which time the low number of planetesimals remaining in the dynamical simulations causes the impact rate to drop artificially. The lunar timeline obtained from these dynamical simulations using nominal values for the masses of each contributing reservoir is at odds with both the calibrated Neukum (Neukum et al., 2001) and Werner (Werner et al., 2014; chronologies. For Mars, the match with its calibrated Werner chronology is no better; by increasing the mass of the E-belt by a factor of four the dynamical lunar and martian chronologies are in line with that of Werner (2019) and match constraints from the current population of Hungaria asteroids. Yet, neither of our dynamical timelines fit well with that of Neukum. The dynamical lunar and martian chronologies are also different from each other. Consequently, the usual extrapolation of such chronologies from one planetary body to the other is technically inappropriate.

“…In contrast, Earth accreted mostly from enstatite chondrite-like sources (Dauphas, 2017;Brasser et al, 2018;Javoy et al, 2010), which has a far lower water content (~0.01 wt%) (Hutson and Ruzicka, 2000) than ordinary chondrite (~0.1 wt%) (McNaughton et al, 1981;Robert et al, 1977Robert et al, , 1979. Based on these analyses, we conclude that the higher portion of ordinary chondrite (Woo et al, 2018;Brasser et al, 2018) together with the low fraction of water-rich carbonaceous chondrite (5 -10 wt%) (Kerridge, 1985;Robert and Epstein, 1982) delivered most of the martian water. The total estimated initial martian water budget from the coupled dynamical-cosmochemical modeling results of Brasser et al (2018) and Woo et al (2018) corresponds to ~600 ppm, which is somewhat higher than Mars' current computed bulk water content of 300 ±150 ppm (Taylor, 2013).…”

Section: A Temporary Hydrogen Atmosphere As a Byproduct Of Colossal Imentioning

confidence: 70%

“…Based on these analyses, we conclude that the higher portion of ordinary chondrite (Woo et al, 2018;Brasser et al, 2018) together with the low fraction of water-rich carbonaceous chondrite (5 -10 wt%) (Kerridge, 1985;Robert and Epstein, 1982) delivered most of the martian water. The total estimated initial martian water budget from the coupled dynamical-cosmochemical modeling results of Brasser et al (2018) and Woo et al (2018) corresponds to ~600 ppm, which is somewhat higher than Mars' current computed bulk water content of 300 ±150 ppm (Taylor, 2013). If most of the water in the martian mantle outgassed during magma ocean solidification and condensed within ~0.1…”

Section: A Temporary Hydrogen Atmosphere As a Byproduct Of Colossal Imentioning

confidence: 87%

Mars in the aftermath of a colossal impact

Woo

Genda

et al. 2019

Icarus

Self Cite

The abundance of highly siderophile elements (HSEs) inferred for Mars' mantle from martian meteorites implies a Late Veneer (LV) mass addition of ~0.8 wt% with broadly chondritic composition. Late accretion to Mars by a differentiated Ceres-sized (~1000 km diameter) object can account for part of the requisite LV mass, and geochronological constraints suggests that this must have occurred no later than ca. 4480 Ma. Here, we analyze the outcome of the hypothetical LV giant impact to Mars with smoothed particle hydrodynamics simulations together with analytical theory. Results show that, in general about 50% of the impactor's metallic core shatters into ~10 m fragments that subsequently fragment into sub-mm metallic hail at re-accretion. This returns a promising delivery of HSEs into martian mantle compared to either a head-on and hit-and-run collision; in both cases, less than 10% of impactor's core materials are fragmented and finally embedded in the martian mantle. Isotopic evidence from martian meteorites, and interpretations from atmospheric mapping data show that a global surface water reservoir could be present during the early Noachian (before ca. 4100 Ma). The millimeter-sized metal hail could thus react with a martian hydrosphere to generate ~3 bars of H2, which is adequate to act as a greenhouse and keep early Mars warm. Yet, we also find that this atmosphere is transient.It typically survives shorter than 3 Myr based on the expected extreme ultraviolet (EUV) flux of the early Sun; if the Sun was a slow rotator an accordingly weaker EUV flux could extend this lifetime to more than 10 Myr. A dense pre-Noachian CO2 atmosphere should lower the escape efficiency of hydrogen by IR emission. A more detailed hydrodynamic atmospheric model of this early hydrogen atmosphere is warranted to examine its effect on pre-Noachian Mars.