Migration of Celestial Bodies to Earth from Various Solar System Regions

Core Concepts

N-body simulations reveal that Earth and Venus likely accreted similar planetesimals, and a significant portion of Earth's water could originate from beyond Jupiter's orbit.

Abstract

• Bibliographic Information: Ipatov, S.I. (2022). Migration of bodies to the Earth from different distances from the Sun. In Astronomical hazards for life on Earth (IAU Symposium No. 374). International Astronomical Union.

• Research Objective: This paper investigates the migration patterns of celestial bodies in the early Solar System and calculates the probabilities of their collisions with Earth and other terrestrial planets to understand the implications for planetary accumulation and water delivery.

• Methodology: The study employs N-body simulations using the Swift integration package to model the gravitational interactions between planetesimals and planets. Two models are used: Model C simulates collisions within the terrestrial planet zone, while Model MP focuses on migration from the outer Solar System, calculating collision probabilities.

• Key Findings:

  • Earth and Venus likely accumulated similar planetesimals during their late stages of formation.
  • A substantial amount of water, potentially exceeding the mass of Earth's oceans, could have been delivered to Earth from regions beyond Jupiter's orbit.
  • The outer asteroid belt is identified as a potential source of the Late Heavy Bombardment.
  • Impact velocities for bodies originating from the Jupiter and Saturn zones are estimated to be 23-26 km/s for Earth and 20-23 km/s for the Moon.

• Main Conclusions: The findings suggest a dynamic early Solar System where material exchange between different regions significantly influenced the composition and evolution of the terrestrial planets, particularly regarding water delivery to Earth.

• Significance: This research provides valuable insights into the processes that shaped the early Solar System and the likelihood of collisions between planets and migrating bodies, contributing to our understanding of planetary formation and the origins of water on Earth.

• Limitations and Future Research: The study acknowledges limitations in accurately determining the composition of early planetesimals and suggests further research on the evolution of the number of near-Earth objects over time.

Stats

The probability of collisions of bodies during their dynamical lifetimes with the Earth could be up to 0.001-0.01 for some initial semi-major axes between 3.2 and 3.6 AU.
The probabilities of collisions of bodies with the Earth did not exceed 10−5 at initial semi-major axes between 12 and 40 AU.
The total mass of water delivered to the Earth from beyond Jupiter’s orbit could exceed the mass of the Earth’s oceans (∼2 · 10−4mE), assuming a total planetesimal mass of about 100mE (where mE is the mass of the Earth).
The ratio of the total mass of the material delivered from beyond the orbit of Jupiter to a planet to the mass of the planet was about two times greater for Mars than that for the Earth.
The characteristic velocities of collisions of bodies from the feeding zone of the terrestrial planets with the Moon varied mostly from 8 to 16 km/s, and velocities of collisions with the Earth were from 13 to 19 km/s.
The velocities of collisions with the Moon of bodies that came from the feeding zones of Jupiter and Saturn were mainly from 20 to 23 km/s, while for the Earth this range was from 23 to 26 km/s.

Quotes

Key Insights Distilled From

Migration of Bodies to the Earth from Different Distances from the Sun

by S.I. Ipatov at arxiv.org 11-12-2024

https://arxiv.org/pdf/2411.06777.pdf

Deeper Inquiries

How might the discovery of exoplanetary systems with different migration histories inform our understanding of the uniqueness of Earth's formation and water acquisition?

Discovering and characterizing exoplanetary systems with diverse migration histories can provide invaluable insights into the uniqueness of Earth's formation and water acquisition. Here's how:

Comparative planetology: Studying exoplanetary systems, especially those with terrestrial planets in their habitable zones, allows us to compare and contrast their architectures and compositions with our own Solar System. This comparative approach helps us understand if the processes that led to Earth's formation and water enrichment were typical or unusual in the grand scheme of planetary system evolution.
Constraining migration models: Observing different planetary configurations and compositions in exoplanetary systems can help validate, refine, or even refute our current models of planetary migration. For instance, the presence or absence of "hot Jupiters" – gas giants orbiting very close to their stars – in different exoplanetary systems can provide clues about the prevalence and efficiency of different migration mechanisms, such as planet-disk interactions or gravitational scattering.
Water delivery mechanisms: By analyzing the atmospheric compositions of exoplanets, particularly those in their systems' habitable zones, we can infer the presence and abundance of water. This data can help us assess the effectiveness of various water delivery mechanisms, such as inward migration of icy planetesimals from the outer regions of planetary systems, as proposed for Earth.
Identifying potential "water worlds": The discovery of exoplanets with significantly different water contents than Earth, including potential "water worlds" with vast oceans, can shed light on the range of possible planetary compositions and the factors influencing water retention during planet formation.
Understanding the role of giant planets: Observing the positions and masses of giant planets in exoplanetary systems can help us understand their role in shaping the orbits and compositions of inner, terrestrial planets. This is crucial for assessing the influence of Jupiter and Saturn on the delivery of water and other volatiles to the early Earth.
In essence, studying the diversity of exoplanetary systems provides a broader context for understanding the processes that shaped our own Solar System. It allows us to move beyond the limitations of studying a single example – our own – and develop a more comprehensive understanding of planet formation, migration, and the emergence of habitable environments.

Could the impact of a single, large water-rich body from the outer Solar System, rather than a gradual accumulation of smaller bodies, better explain the isotopic composition of Earth's oceans?

The idea of a single, large impactor delivering a significant portion of Earth's water, often referred to as a "late veneer," is an active area of research. While the gradual accumulation of water from smaller bodies like asteroids and comets remains the dominant theory, a single impactor model holds some appeal, particularly when considering isotopic compositions.
Here's a breakdown of the arguments:
Arguments for a single impactor:

Matching isotopic ratios: Some studies suggest that the isotopic composition of certain elements in Earth's oceans, like deuterium to hydrogen (D/H) ratios, more closely resemble those found in comets from the outer Solar System rather than asteroids. A single, large impactor originating from the outer Solar System could potentially deliver a significant amount of water with the observed isotopic signature.
Explaining volatile depletion: Earth's relatively low abundance of certain volatile elements compared to its solar abundance could be explained by a late impact stripping away some of the early atmosphere and surface materials. A large impactor could provide the necessary energy for such an event.
Arguments against a single impactor:

Statistical improbability: While not impossible, the probability of a single, sufficiently large and water-rich body impacting the early Earth at the right time and velocity to deliver the observed amount of water is relatively low.
Isotopic heterogeneity: Recent analyses of lunar samples have revealed a wider range of D/H ratios than previously thought, suggesting multiple sources of water for the Earth-Moon system. This finding supports a more gradual accumulation model involving various types of impactors.
Challenges to atmospheric retention: A massive impact could also erode or even completely strip away a significant portion of Earth's early atmosphere, potentially counteracting the delivery of volatiles.
Conclusion:
While a single, large impactor cannot be ruled out, the current evidence leans towards a more complex scenario involving the gradual accumulation of water from various sources, including both asteroids and comets. Further research, particularly on the isotopic compositions of different water reservoirs on Earth and other planetary bodies, is needed to fully resolve this debate.

If we could send probes back in time to analyze the early Solar System, what specific measurements or observations would be most crucial for validating or refuting the proposed models of planetary migration and water delivery?

Sending probes back to the early Solar System would be a game-changer for understanding planetary migration and water delivery. Here are some crucial measurements and observations that would be invaluable:
1. Isotopic Analysis of Protoplanetary Disk:

Target: Gas and dust in the protoplanetary disk at various distances from the young Sun.
Measurement: Isotopic ratios of key elements like hydrogen (D/H), oxygen, and nitrogen.
Significance: Establishing the initial isotopic gradients within the protoplanetary disk would provide a baseline for tracing the origins of volatiles like water in different parts of the Solar System.
2. Composition of Planetesimals and Embryos:

Target: Planetesimals of various sizes and compositions in different regions of the protoplanetary disk, including the asteroid belt and beyond the snow line.
Measurement: Elemental and isotopic compositions, mineralogy, and presence of ices.
Significance: Analyzing the building blocks of planets would reveal the diversity of materials present in different regions of the disk and provide clues about the sources of Earth's water and other volatiles.
3. Dynamical State of the Early Solar System:

Target: Orbits and masses of giant planets and smaller bodies in the early Solar System.
Measurement: Precise astrometry to track orbital movements and gravitational interactions.
Significance: Reconstructing the early orbital architecture of the Solar System would help us understand the role of giant planet migration in scattering planetesimals and potentially delivering water to Earth.
4. Cratering History of Inner Solar System Objects:

Target: Surfaces of the Moon, Mars, and other inner Solar System bodies.
Measurement: Crater size-frequency distributions and ages.
Significance: Determining the timing and intensity of early bombardment events would provide insights into the dynamical evolution of the Solar System and potential periods of heightened water delivery.
5. Early Atmospheres of Terrestrial Planets:

Target: Atmospheres of early Earth, Venus, and Mars.
Measurement: Atmospheric composition, density, and escape rates.
Significance: Analyzing the early atmospheres of terrestrial planets would help us understand the delivery and retention of volatiles, providing clues about the evolution of habitable environments.
By combining these measurements, we could gain an unprecedented understanding of the processes that shaped our Solar System and led to the emergence of Earth as a habitable world.