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

“…assembly, the planet’s feeding zone encompassed enough water-rich material to supply 15–70 terrestrial oceans (TO) of water in the first 70Myr (Morbidelli et al. , 2000; Raymond et al. , 2006; Chassefie`re et al. , 2012); thus a wet in situ formation for Earth-like planets is entirely…”

“Although Earth, Venus, and Mars formed mainly from locally sourced material, the final stages of accretion blurred chemical differences by integrating contributions from elsewhere—Jupiter and Saturn’s wanderings scattered objects in the region presently occupied by the asteroid belt and beyond, delivering water and ot…”

“There are several hypotheses to explain mass loss from the belt (see for example, Morbidelli et al. 2000 and Chambers and Wetherill 2001), but all rely on the presence of unstable resonances with the giant planets.”

“The elimination of bodies from the primordial main belt is likely to have come from a combination of collisions and dynamics, presumably triggered by the formation of Jupiter several Myr after the birth of the Solar System (Wetherill, 1992; Franklin and Lecar, 2000; Morbidelli et al., 2000; Chambers and Wetherill, 200…”

“In the numerical simulations of Morbidelli et al. (2000), some terrestrial planets accreted water-rich embryos, whereas others did not.”

“Similarly, in Morbidelli et al. (2000) , Jupiter is inserted at 10 Myr, while”

“The consequences of water being added at a late stage but before the completion of core formation, as implied by Morbidelli et al. (2000), is discussed in Section 6.”

“This classical model is appealing because it explains the accretion of Mercury- to Earth-sized bodies in the inner Solar System (2; 3; 4; 5) and, possibly, of super-Earth cores in the Jovian planet region (6; 7).”

“The third possibility is that Earth accreted water from primitive planetesimals and/or planetary embryos originally from the outer asteroid belt (Lunine et al. 2007; Morbidelli et al. 2000; O’Brien et al. 2006; Raymond et al. 2004, 2005, 2006, 2007).”

“…came from comets (Delsemme 1994; Owen & Bar-Nun 1995), from oxidation of a primitive, H-rich atmosphere (Ikoma & Genda 2006), from adsorption of water onto small grains at 1 AU (Muralidharan et al. 2008), or from other sources – see Morbidelli et al. (2000) for a discussion of some of these models.”

“Although several studies have considered the accretion of water-bearing material onto the terrestrial planets (e.g. Morbidelli et al., 2000; O’Brien et al., 2014), only two studies have attempted to address the bulk composition of accreted material and its implications for the final compositions of…”

“Nebular models and meteorite data suggest that the local environment during the formation of this planet was sufficiently hot to prevent hydration of the planetesimals and protoplanets out of which the planet was formed (Morbidelli et al., 2000).”

“…most probable original source of Earth’s water was ice, either condensed locally in the planetesimals from which the bulk of Earth was made (Abe et al. 2000), or in more distant planetesimals scattered from what is now the asteroid belt (Morbidelli et al. 2000; Raymond et al. 2004), or in comets.”

“A late veneer has also been invoked as a possible source for bulk Earth’s or silicate Earth’s water (Owen and Bar-Nun 1995; Morbidelli et al. 2000; Dauphas and Marty 2002; Albarede 2009; Marty 2012; Fig.”

“The most probable source of water is a hydrous inner Solar System reservoir at approximately 1 AU , but we cannot formally rule out a single wet planetary embryo from the asteroid belt or a large comet with the appropriate elemental and isotopic characteristic”

“It is hard to explain the abundances of the other noble gases in the atmosphere today unless some volatiles came to Earth from another source, such as impacts by comets or asteroids [36,37].”

“…mixing and transport processes in the gaseous disk ( e.g ., Boss, 2004), as well as those produced by the chaotic orbital evolution of planetesimals ( e.g ., Morbidelli et al. , 2000), can have a significant effect on the radial distribution of volatiles and their delivery to planetary surfaces.”

“Even greater interest is added by the possibility that the outer asteroid belt may have supplied part of the volatile inventory of the Earth (Morbidelli et al. 2000).”

“The inner Solar System was too warm to have retained water ice, so 33 terrestrial water is thought to have been supplied by hydrated materials that originally formed 34 in the outer Solar System before migrating inwards (4, 5).”

“As suggested by Morbidelli et al. (2000), the asteroid belt may be cleared simply by self-scattering of bodies onto unstable orbits such as resonances with Jupiter.”

“The models emphasize that the terrestrial planets are formed from material sourced throughout the inner Solar System, with perhaps approximately 10 per cent of material forming the Earth coming from beyond the ‘snow line’ at greater than 3 AU, (Morbidelli et al. 2000; Morbidelli 2007).”

“However, recent models of solar system formation (e.g., Morbidelli et al. 2000; Raymond et al. 2004) suggest a wet early Venus (e.g., Dayhoff et al. 1967; Walker et al. 1970; Donahue and Pollack 1983; Kasting and Pollack 1983) because the suggest that most of Earth’s water came from the asteroid…”

“This flux of carbonaceous chondrite is comparable to that estimated for the Earth (Morbidelli et al., 2000; Becker et al., 2006) after accounting for the difference in accretion cross section, which is 50–200× lower for the Moon (Bottke et al., 2007; Nesvorny et al., 2012; Schlichting et al., 2012).”

“, Krot, A. N., Hutcheon, I. D., and Ulyanov, A. A. (2002). Lead Isotopic Ages of Chondrules and Calcium-Aluminum-Rich Inclusions. Science, 297, 1678–1683. Bottke, W. F., Walker, R. J., Day, J. M. D., Nesvorny, D., and Elkins-Tanton, L. (2010). Stochastic Late Accretion to Earth, the Moon, and Mars. Science, 330, 1527–…”

“Earth’s water content is consistent with the accretion of 2.5−25×10−3 M⊕ of C-type material (Morbidelli et al., 2000; Marty, 2012).”

“While there is observational evidence from the asteroid belt that the Solar-System snow line is near Rsnow,⊙ = 2.7 AU (Morbidelli et al. 2000), there is considerable uncertainty on how this scales with stellar mass (Sasselov & Lecar 2000; Kennedy & Kenyon 2008).”

“These orbits are unstable on a long timescale and represent a potential source of impactors for the Late Heavy Bombardment, as shown by Morbidelli et al. (2000b).”

“Through this process, carbonaceous chondrites were enriched in hydrogen, and could therefore have contributed an important source of water on Earth (e.g. Morbidelli et al., 2000; Dauphas, 2000; Albarède, 2009; TrigoRodrı́guez and Martin-Toress, 2012).”

“…planets were too hot for hydration of planetesimals and that the inventory of water on the Earth and other terrestrial planets came primarily from water-rich embryos that formed farther from the Sun and were scattered inward by interactions with the gas-giant planets (Morbidelli et al., 2000).”

“…HZs of lower-mass stars – is inefficient dynamical stirring in the low-mass disks found around low-mass stars, because more massive embryos are needed to increase eccentricities enough for significant radial mixing and therefore water delivery (Morbidelli et al. 2000; Raymond et al. 2004, 2007).”

“…materials are delivered via volatile-rich planetesimals - of chondritic composition (e.g., Drake and Righter 2002; Alexander et al. 2012; Marty 2012; Bouvier and Boyet 2016) - from the outer Solar System to accreting protoplanets (e.g. Morbidelli et al. 2000; Raymond et al. 2009; Marty 2012).”

“…using the Asteroid Belt as a constraint for their model outcomes, both for delivering water-rich asteroid material to the growing planets (Morbidelli et al., 2000), and also for using their orbits to rule out other modes of planet migration (Minton and Malhotra 2009, Walsh and Morbidelli…”

“However, the presence of pyroclastic volcanism on Mercury suggests that the devolatilization of the planet was not complete, or that the initial volatile budget of the planet was greater than previously hypothesized, perhaps due to the incorporation during accretion of planetesimals formed over a large range of solar…”

“In the classical model of accretion, water-rich planetesimals originated in the outer asteroid belt (Morbidelli et al. 2000; Raymond et al. 2007a, 2009; Izidoro et al. 2015).”

“%) cometary contribution to terrestrial volatiles may be likely (Morbidelli et al., 2000).”

“Recent dynamical [41] and geochemical [43] evidence support the idea that the Earth accreted wet, thus removing any requirement for a drastic change in the nature of the material accreted by our planet.”

“The evidence points to about 2.7 AU, in the outer asteroid belt where icy C-class asteroids abound (Abe et al. 2000; Morbidelli et al. 2000; Rivkin et al. 2002).”

“According to Morbidelli et al. (2000), Lunine et al. (2003) the equivalent of ∼0.1 terrestrial ocean of H2O, that is a ∼300 m deep EGL of water, could have been provided to Earth by comets during the few 100 Myr following main accretion.”

“Morbidelli et al. (2000) have shown that up to 15% of the mass of the Earth could be accreted late in Earth’s growth by collision of one or a few asteroids originating in the Main Belt.”

“…Venus, and Mars, present-day atmospheres indicate that water and carbon dioxide have remained since accretion, though perhaps the bulk of volatiles were delivered toward the end of accretion (e.g., Morbidelli et al. 2000; Chambers 2006; Raymond et al. 2006; O’Brien, Morbidelli, & Levison 2006).”

“…integra (Levison and Duncan, 1994) until it was ejected on hyp bolic orbit or entered into collision with a giant planet. total collision probability with Mars (assumed to be on present orbit) is computed over the test particle’s lifeti with the method discussed in Morbidelli et al. (2000).”

“Earth’s water originally accumulated during planetary accretion (Wood et al., 2010) and/or soon afterward (Albarede, 2009) by delivery from asteroids (Morbidelli et al., 2000) and comets (Hartogh et al., 2011).”

“Also, the effects of core segregation depend on the fraction of metal equilibrated with volatile-bearing silicate [43], as much of the core may have segregated prior to bulk volatile delivery [44].”

“(C) Much of the BSE inventory of C was delivered as part of a late veneer that post-dated core formation (Morbidelli et al., 2000; Dauphas and Marty, 2002; Javoy, 2005).”

“1B) (9): The atmosphere was partly eroded and transformed (10, 11), and the hydrosphere was enriched by water (12, 13).”

“While the means of delivery of water to Earth remain a subject of debate (Morbidelli et al. 2000), the synthesis of water in the Universe is a fundamental link in establishing our origins.”

“In a homogeneous accretion model, volatiles are incorporated throughout the accretion of a growing body, from the early stages when the solar nebula was still present until the final stages of growth of planetary embryos (Bottke et al., 2010; Morbidelli et al., 2000).”

“The mechanism for delivering a veneer of water to an otherwise dry Earth is controversial, although primitive carbonaceous chondrites provide the best match to the D/H ratio of the Earth’s oceans (for an overview, see Morbidelli et al. 2000).”

“We propose a bimodal model for water delivery to Earth-like planets, which is a direct out-growth of our simulations that included a larger number of particles than the pioneering simulations of Morbidelli et al. (2000).”

“Additionally, accretion event of asteroids seems to be stochastic event (e.g., Morbidelli et al., 2000; Petit et al., 2001).”

“Notably, the link between distant Vestoids and HEDs is provided by several V-types observed among nearEarth objects (e.g., Marchi et al. 2005).”

“Impacts from comets and asteroids delivered a variety of organics to early Earth, even though they provided only a very small fraction of Earth’s water budget (Morbidelli et al., 2000).”

“e planetesimals forms a massive steam atmosphere that ends up the ocean after its cooling (Lange and Ahrens 1982; Matsui and Abe 1986; Zahnle et al. 1988). Water-containing rocky planetesimals (e.g., Morbidelli et al. 2000; Raymond et al. 2004, 2005) and/or icy planetesimals (e.g., Gomes et al. 2005) can be delivered…”

“At the same time, work by Gillmann et al. (2009), Morbidelli et al. (2000), and Raymond et al. (2006) shows that Venus’ initial water inventory at formation could be as much as two terrestrial ocean’s worth while large planetary embryos could deliver much more within 200 Myr of formation.”

“…then their growth would be similar to that of Solar System’s terrestrial planets (Wetherill 1990, 1996; Chambers & Wetherill 1998; Agnor et al. 1999; Morbidelli et al. 2000; Chambers 2001; Kenyon & Bromley 2006), but minus the dynamical effects of Jupiter and Saturn (although giant planets may…”

“(2.5–4 AU) are up to 10% water by mass, while those originating from the inner asteroid belt (∼ 2 AU) range from 0.05–0.1% water by mass (Morbidelli et al. 2000).”

“Meanwhile, the slightly lower D/H values observed in carbonaceous chondrites (ranging from 0.8 to 2.1 VSMOW; Lecuyer et al. 1998) stimulated a hypothesis that water was delivered by proto-asteroids rich in chondritic material (Morbidelli et al. 2000; Dauphas et al. 2000).”

“Addition of volatiles from the outer Solar System carried by debris of undifferentiated planetesimals, the so-called late veneer, during the clearing stages of the debris disk, is consistent with current understanding of accretion dynamics (Albarède, 2009; Morbidelli et al., 2000; Robert, 2001).”

“This mode of transport is similar to the model of Morbidelli et al. (2000) except that it is substantially enhanced by the large eccentricities induced by close encounters between the migrating giant planet and the smaller bodies.”