Silicon isotopes in lunar rocks: Implications for the Moon’s formation and the early history of the Earth

Armytage, R. M. G.; Georg, R. Bastian; Williams, Helen M.; Halliday, Alex N.

doi:10.1016/j.gca.2011.10.032

Cited by 142 publications

(102 citation statements)

References 49 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We focus on Theia's oxygen composition since it has been the subject of so much past work, but the Moon is also known to be isotopically similar to the Earth for tungsten, silicon, chromium, and titanium (Touboul et al 2007;Armytage et al 2012;Zhang et al 2012). Presumably, the isotopes of these other elements all had their own unique distributions in the protoplanetary disk that were different from oxygen.…”

Section: Resultsmentioning

confidence: 99%

“…During the time required for mixing, however, the outer portion of the disk would have already cooled and begun accreting into the Moon. In addition, in this scenario, one would expect refractory elements to exhibit stronger isotopic differences between the Earth and Moon since they would have condensed into solids faster, yet such a trend is not seen (Zhang et al 2012;Armytage et al 2012). …”

Section: Theia and The Moon-forming Impactmentioning

confidence: 99%

See 1 more Smart Citation

The feeding zones of terrestrial planets and insights into Moon formation

Kaib

Cowan

2015

Icarus

105

View full text Add to dashboard Cite

The final stage of terrestrial planet formation consists of several hundred approximately lunar mass bodies accreting into a few terrestrial planets. This final stage is stochastic, making it hard to predict which parts of the original planetesimal disk contributed to each of our terrestrial planets. Here we present an extensive suite of terrestrial planet formation simulations that allows quantitative analysis of this process. Although there is a general correlation between a planet's location and the initial semi-major axes of its constituent planetesimals, we concur with previous studies that Venus, Earth, and Mars analogs have overlapping, stochastic feeding zones. We quantify the feeding zone width, ∆a, as the mass-weighted standard deviation of the initial semi-major axes of the planetary embryos and planetesimals that make up the final planet. The size of a planet's feeding zone in our simulations does not correlate with its final mass or semi-major axis, suggesting there is no systematic trend between a planet's mass and its volatile inventory. Instead, we find that the feeding zone of any planet more massive than 0.1M ⊕ is roughly proportional to the radial extent of the initial disk from which it formed: ∆a ≈ 0.25(a max − a min ), where a min and a max are the inner and outer edge of the initial planetesimal disk. These wide stochastic feeding zones have significant consequences for the origin of the Moon, since the canonical scenario predicts the Moon should be primarily composed of material from Earth's last major impactor (Theia), yet its isotopic composition is indistinguishable from Earth. In particular, we find that the feeding zones of Theia analogs are significantly more stochastic than the planetary analogs. Depending on our assumed initial distribution of oxygen isotopes within the planetesimal disk, we find a ∼5% or less probability that the Earth and Theia will form with an isotopic difference equal to or smaller than the Earth and Moon's. In fact we predict that every planetary mass body should be expected to have a unique isotopic signature. In addition, we find paucities of massive Theia analogs and high velocity moon-forming collisions, two recently proposed explanations for the Moon's isotopic composition. Our work suggests that there is still no scenario for the Moon's origin that explains its isotopic composition with a high probability event.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Theia and The Moon-forming Impactmentioning

confidence: 99%

The feeding zones of terrestrial planets and insights into Moon formation

Kaib

Cowan

2015

Icarus

105

View full text Add to dashboard Cite

show abstract

“…A few rock reference materials are also commonly used as δ 30 Si isotopic standards to determine accuracy and reproducibility of solid samples with a complex matrix, especially BHVO-1 and BHVO-2 (e.g. Abraham et al, 2008;Armytage et al, 2012). As exemplified by the offsets between studies measuring δ 30 Si(OH) 4 in seawater discussed above, these standards are of limited use for identifying sample preparation biases among laboratories analyzing seawater Si isotopes.…”

Section: Introductionmentioning

confidence: 99%

GEOTRACES inter-calibration of the stable silicon isotope composition of dissolved silicic acid in seawater

Grasse

Brzezinski

Cardinal

et al. 2017

J. Anal. At. Spectrom.

View full text Add to dashboard Cite

show abstract

“…An impactor that is substantially more Earth-like than Mars but still within the distribution of impactor compositions found in Pahlevan and Stevenson's analysis [14] implies |δf T | < 15% for consistency with the Earth-Moon oxygen similarity. In addition to oxygen, the isotopic compositions of multiple other elements also now appear essentially identical in the silicate Earth and Moon, including chromium [18], titanium [19], tungsten [20] and silicon [21]. This suite of similarities seems to require that the Earth and Moon formed from a nearly identical mix of impactor and target material.…”

Section: (A) Constraintsmentioning

confidence: 97%

Lunar-forming impacts: processes and alternatives

Canup

2014

Phil. Trans. R. Soc. A.

View full text Add to dashboard Cite

The formation of a protolunar disc by a giant impact with the early Earth is discussed, focusing on two classes of impacts: (i) canonical impacts, in which a Mars-sized impactor produces a planet-disc system whose angular momentum is comparable to that in the current Earth and Moon, and (ii) high-angularmomentum impacts, which produce a system whose angular momentum is approximately a factor of 2 larger than that in the current Earth and Moon. In (i), the disc originates primarily from impactorderived material and thus is expected to have an initial composition distinct from that of the Earth's mantle. In (ii), a hotter, more compact initial disc is produced with a silicate composition that can be nearly identical to that of the silicate Earth. Both scenarios require subsequent processes for consistency with the current Earth and Moon: disc-planet compositional equilibration in the case of (i), or large-scale angular momentum loss during capture of the newly formed Moon into the evection resonance with the Sun in the case of (ii).

show abstract

Silicon isotopes in lunar rocks: Implications for the Moon’s formation and the early history of the Earth

Cited by 142 publications

References 49 publications

The feeding zones of terrestrial planets and insights into Moon formation

The feeding zones of terrestrial planets and insights into Moon formation

GEOTRACES inter-calibration of the stable silicon isotope composition of dissolved silicic acid in seawater

Lunar-forming impacts: processes and alternatives

Contact Info

Product

Resources

About