Source regions and timescales for the delivery of water to the Earth

“A fraction of such bodies would have been accreted by Earth, stochastically delivering volatiles to the young planet (Morbidelli et al. 2000; O’Brien et al. 2006; Raymond et al. 2009).”

“As noted, Earth was more likely to accrete planetary embryos from farther away during the second half its accretion, including 10–25% from beyond 1.5AU and some wetter ones from the outer asteroid belt at 2.5–3.5AU (Morbidelli et al., 2000; Chambers, 2004; Raymond et al., 2004).”

“To answer these questions, we rely on N-body simulations of interacting planetary embryos and planetesimals (e.g., Morbidelli et al. 2000; Chambers 2001; Raymond et al. 2004, 2006, 2007).”

“Obviously, this ratio is needed in order to evaluate the contribution of comets for transferring water in Earth’s oceans (Morbidelli et al. 2000; Raymond et al. 2004; Villanueva et al. 2009), directly associated with the emergence of life.”

“Morbidelli et al. (2000) modeled comet trajectories in the nascent solar system.”

“…that Mars and Venus both started out, like Earth, hot from accretional energy and impacts and wet from impacts of large hydrous (5– 20% water) asteroids from the outer asteroid belt (Morbidelli et al. , 2000, 2012) and other ‘‘wet’’ accretionary material (Drake and Righter, 2002; Drake, 2005).”

“The outer asteroids are icy C-class objects (e.g. Abe et al. 2000; Morbidelli et al. 2000) whereas the inner asteroid belt is largely devoid of water.”

“One of available sources for the water on the planets is delivery of icy planetesimals from the regions beyond the ice line (Morbidelli et al. 2000), although the possibility of forming H2O through chemical interaction between the planetary magma ocean and primitive H2 atmosphere is also pointed…”

“Earth is believed to have accumulated most of its water and other volatiles from solid bodies that condensed outward of the orbit of Mars and were accreted by Earth toward the end of or subsequent to the major phases of our planet’s growth (Morbidelli et al. 2000).”

“Such events could be, for example, evaporation that could reduce the planetary gas mass envelope (e.g. Baraffe et al. 2004), or later accretion of icy bodies (see e.g. Morbidelli et al., 2000 in the case of the Earth).”

“The current consensus is that Earth acquired most its water by accretion of carbonaceous chondrite material, particularly CI-like chondrites, from beyond the snow line in the solar nebula (Alexander et al., 2012; Marty, 2012; Morbidelli et al., 2000; Sarafian et al., 2017).”

“It too may have issues matching the measured D/H of the Earth, but a bigger issue is that the delivery efficiency of comets is very low (Morbidelli et al. 2000), such that even delivering a single Earth ocean of water is unlikely.”

“It is reasonable to assume that at this stage small planetesimals, collision-related fragments and dust collided with the Earth ( Morbidelli et al., 2000 ).”

“…then f O2 matters throughout the entire history of core formation, but if a greater portion of the volatiles were added to Earth during the later stages of accretion (Morbidelli et al., 2000) then the f O2 prevailing during earlier stages has little influence on core storage of these elements.”

“One technique is to simulate the growth history of an evolving distribution of protoplanets using numerical techniques (e.g. Chambers and Wetherill, 1998; Kokubo and Ida, 1998; Agnor et al., 1999; Morbidelli et al., 2000; Raymond et al., 2006); the other is to infer planetary core formation timescales using geochemica…”

“Morbidelli et al. (2000) have shown that a small fraction of asteroidal material from the Main Belt accreted to Earth.”

“…to be the most realistic, since water is mainly accreted in the time range Please cite this article as: Gillmann, C., et al., A consistent picture of earl and Ar isotopic ratios and low oxygen atmospheric content, Earth Plan from 10 Myr to ≈50 Myr (Morbidelli et al., 2000, Raymond et al., 2006).”

“Thus, material would not be expected to exist in these zones, at least after the gas-dominated disk was dispersed; Cen may thus have dry terrestrial planets, devoid of the C/H2O-based life that thrives on Earth.”

“…to space, delivery from planetary embryos and comets, and outgassing / subduction) have a fundamental and still poorly constrained influence (e.g, Morbidelli et al. 2000; Hirschmann and Withers 2008; Lammer et al. 2008; Lenardic and Crowley 2012; Wordsworth and Pierrehumbert 2013; Dong et al.…”

“…hydrogen was contained in the chondritic material from which Earth accreted, with a possible contribution from icy objects that formed beyond the snow line in the outer solar system and were later scattered inward (Morbidelli et al., 2000; Marty and Yokochi, 2006; Rubie et al., 2011; Marty, 2012).”

“Although the asteroid belt could be an important source for Earth’s water (Morbidelli et al. 2000), thermal models have shown that surfaces of most asteroids are too hot for water ice to remain stable against sublimation (see Schorghofer 2008 and Sect.”

“Primitive outer asteroidal material (C-complex) is a likely source of Earth’s water (Morbidelli et al. 2000; Raymond et al. 2004, 2007).”

“In the classical model of solar system formation (Wetherill 1992), Earth’s water is a byproduct of its broad feeding zone (Morbidelli et al. 2000; Raymond et al. 2004, 2007a).”

“However, volatile accretion is unlikely to be a problem as simulations indicate that planets commonly acquire large volatile inventories (i.e., Earth-like or larger) during late stage planet formation [Morbidelli et al., 2000; Raymond et al., 2004].”

“Addition of volatiles by late accretion of cometary material is also a possibility (Morbidelli et al., 2000), but not necessity.”

“Given the potential importance of asteroid impacts as a source of water to the early Earth (Delsemme 2000; Morbidelli et al. 2000) and the possible use of asteroids for resource utilization purposes (Lewis et al.”

“Indeed it has been suggested (Morbidelli et al., 2000; Lunine, 2006) that the Earth current supply of water was delivered mostly by asteroids, not comets, some time following the collision that produced the Moon (which wouldhave vaporized any of the water existing at that time).”

“Water-rich embryos from the outer asteroid belt can contribute significantly to the overall water budget of any given terrestrial planet (72).”

“Then, mass loss on the AGB would have moved the star’s Kuiper Belt out another factor of about 3.”

“…for their potential to constrain theoretical studies indicating that material from the asteroid belt region could have been a significant primordial source of the water and other volatiles on Earth (e.g., Morbidelli et al., 2000; Raymond et al., 2004; O’Brien et al., 2006; Hsieh, 2014a).”

“A complete discussion of this topic is far beyond the scope of this paper (for robust reviews of various ideas see Morbidelli et al. (2000), Morbidelli et al. (2012) and Marty et al. (2016)).”

“story of planetary accretion in the early Solar System and its evolution (Chambers and Wetherill, 1998; Morbidelli et al., 2000; Blum and Wurm, 2008).”

“We adopt the model of Morbidelli et al. (2000), who argued that water-rich bodies originating in the solar system’s asteroid belt were the primary source of Earth’s water, and simulate the late stage of terrestrial planet formation (Wetherill 1996) by numerically integrating the orbits of a few…”

“…gravitational disturbance of the asteroid belt region by Jupiter, it has been proposed that a large fraction of asteroids is ejected, some of which collide with Earth (Morbidelli et al., 2000; Raymond et al., 2009), which is consistent with the extreme mass depletion of the present asteroid belt.”

“The effect of radial sampling on the bulk composition of rocky planets was first explored by Barshay (1981) and considered much later in the astronomical community (e.g., Morbidelli et al. 2000; Bond et al. 2010a, 2010b; Elser et al. 2012; Thiabaud et al. 2014).”

“A variety of mechanisms have been proposed to account for the Earth’s water budget, with many studies favoring the delivery of water from asteroidal material (e.g., Albarede et al., 2013; Alexander et al., 2012; Morbidelli et al., 2000; Raymond et al., 2009), which we consider here.”

“First, we must recognize that a wide range of water fractions are possible for terrestrial exoplanets ( e.g. , Morbidelli et al., 2000; Le´ger et al., 2004; Raymond et al., 2004; Bond et al., 2010).”

“…of the origin of Earth’s water suggest that a significant fraction of Earth’s water was delivered to its accretion zone by water-rich planetesimals and planetary embryos from past 2 AU (Morbidelli et al., 2000; Raymond et al., 2004; 2006; 2007; 2009; O’Brien et al., 2006; Izidoro et al., 2013).”

“The three central theories presently used to describe the incorporation of water are based on the origin of the water-bearing material and whether the water was incorporated during or after accretion (Ciesla and Lauretta, 2005; Drake, 2005; Lunine et al., 2003; Morbidelli et al., 2000).”

“…of D/H is especially important since it allows to limit the contribution of comets to the terrestrial water, the high D abundance implying that no more than about 10 to 30% of Earth’s water can be attributed to comets (e.g. Eberhardtet al. 1995, Dauphas et al. 2000, Morbidelli et al. 2000).”

“…to have been delivered by water-rich planetesimals that were gravitationally scattered into the inner Solar System either by asteroidal embryos (Morbidelli et al. 2000; Raymond et al. 2007) or by Jupiter during its growth and/or migration (Walsh et al. 2011; Raymond & Izidoro 2017; O’Brien et…”

“…the origin of the Earth’s water is strong evidence that it came from exogenous sources because the solar nebula was too hot in the terrestrial planet-formation zone to form waterrich planetesimals from smaller icy precursors (Boss 1998; Morbidelli et al. 2000; Min et al. 2011; Elser et al. 2012).”

“…the one that we favor is that the Earth accreted water 1436 from primitive planetesimals and/or planetary embryos originally from the outer 1437 asteroid belt (Morbidelli et al., 2000; Raymond et al., 2004, 2005, 2006, 2007; 1438 …”

“For example, the fundamental question of how this planet became habitable i.e. accreted and retained water, is still hotly debated (see Morbidelli et al., 2000 for a recent discussion).”

“…HZ to that of SMOW (Tables 4, 5 and 6), the amount of necessary cometary water in some cases agrees very well with previous studies [e.g., ≤ 10% as in Morbidelli et al. (2000), up to 12% as in Deloule, Robert & Doukhan (1998), and up to 15% as in Owen & Bar-Nun, (2000)] giving relevance to locally…”

“Simulations (Morbidelli et al., 2000; Raymond et al., 2004) suggest that a water-rich Earth is quite likely, but the stochastic nature of the outcomes 56 Formation of Earth’s Core”

“%) of the Earth’s water could have its origin in comets (Morbidelli et al. 2000; Drake 2005).”

“In modeling the redistribution of planetary embryos in the early solar system, it was shown that the observed D/H ratio for the Earth can be achieved by having it accrete several carbonaceous-type embryos from the outer asteroid belt [6].”

“In terms of water content, if I naively assume that only material beyond 3 AU has a water content (Morbidelli et al. 2000), and when pegging this at 5 % by mass (Morbidelli et al. 2000), then the putative Mars should have approximately 0.1– 0.2 % by mass in water.”

“Morbidelli et al. (2000) and Mottl et al. (2007) summarize our understanding of the origin of water on Earth.”

“N-body simulations of terrestrial planet formation from disks that extend out close to the orbit of Jupiter are supportive of this idea and all demonstrate substantial mixing of water rich material into the inner disk (e.g. Morbidelli et al. 2000; Chambers 2001; Raymond et al. 2004, 2005a,b).”

“(iii) The origins of Earth’s water and volatiles more generally are the subject of considerable debate (e.g., Anders and Owen, 1977; Carr and Wänke, 1992; Owen and Bar-Nun, 1995, 2000; Javoy, 1998; Caffee et al., 1999; Righter and Drake, 1999; Abe et al., 2000; Morbidelli et al., 2000).”

“Our understanding of the chemical and physical behavior of water permits the application of powerful models to predict its distribution within an accreting solar system and (to a lesser extent) its trajectory on an evolving planet (Morbidelli et al., 2000; Raymond et al., 2005).”

“An interpretation of the origin of terrestrial water from current data is that it was brought to Earth by carbonaceous chondrites (Morbidelli et al. 2000; see review by Alexander et al., 2018) and the ocean water was enriched in D by hydrolysis of D-rich organic compounds.”