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

“Much of the current interest in studying MBCs lies in the possible role of main-belt objects in the primordial delivery of terrestrial water (e.g., Morbidelli et al. 2000).”

“Apparently, nearly all Earth’s water came from large bodies in the region of the outer asteroid belt (Morbidelli et al., 2000).”

“volatiles are naturally incorporated into growing planets if the planets’ feeding zones extend out far enough [334, 427, 429].”

“…building blocks consisted of material that formed in orbital locations just beyond the ice line which could have contained ≈ 0.1 − 0.2 wt% of H2O, while embryos formed in Earth’s orbit should have had lower values within a range of ≈ 0.05− 0.1 wt% (e.g. Morbidelli et al., 2000; Brasser, 2013).”

“First, we expect that many terrestrial planets will be dry because post-formation delivery of volatiles via planetesimals and comets is a stochastic process (Morbidelli et al. 2000).”

“For example, in the Solar System, Ceres, the most massive asteroid, has a mean density of 2.1 g cm−3 suggesting ∼25% of its mass is water (McCord & Sotin 2005, Thomas et al. 2005).”

“At 1 AU, it is likely that grains were too hot to be sufficiently coated with ices and instead the Earth potentially received its water from impacts of bodies that originate beyond the nebular snow line near 2.5 AU (e.g. Morbidelli et al. 2000, but see also Drake 2004).”

“Following Albarède et al. (2009), the local planetesimals were dry and the water has to come from asteroids and comets from the Jupiter-Saturn region or comets from the trans-Uranian region (Morbidelli et al., 2000).”

“The late delivery of water from comets or watery asteroidal objects 83 is dynamically plausible, as more distant material would impact Earth at later times 74 .”

“In the Solar System, meteoritic evidence [238] places the transition between water vapor and water ice, which occurs at a mid-plane temperature of 150-180 K, at around 2.”

“The leading explanation for the delivery of water to Earth is that water-bearing, asteroid-like bodies from beyond the snow line were gravitationally scattered inward and accreted by the planet during its growth (e.g. Morbidelli et al. 2000).”

“These discoveries have important implications for the delivery of water to a dry Earth, a task that appears most readily accomplished by primordial asteroids – planetary embryos analogous to Ceres – in the outer main belt (Morbidelli et al. 2000).”

“2”

“[200] describe the delivery of water to Earth during planetary formation and do not provide a good constraint on the amount of water, let alone the distribution of delivered water in the different parts of Earth, e.”

“It is during this late stage that water may be accreted by terrestrial planets in the form of water-rich bodies originating past ∼ 2.5 AU (Morbidelli et al. 2000; Raymond, Quinn & Lunine 2004 – hereafter RQL04; see Drake & Righter 2002 for a different opinion).”

“Indeed, such ratios are seen in other bodies in the outer solar system, with comets and icy satellites having water mass fractions of ∼40-50% (e.g. Delsemme 1992; Morbidelli et al. 2000; Schubert et al. 2010; A’Hearn 2011, and references within).”

“A significant fraction of 8 9 Earth’s water likely came from Kuiper Belt comets (Morbidelli et al. 2000).”

“Early accretion models suggest that the water was injected into the inner Solar System (carried typically by bodies from beyond the ice-line but within the asteroid belt) whilst the planets were themselves accreting (e.g. Morbidelli et al. 2000; Petit et al. 2001).”

“Therefore, much of Earth’s water was likely derived from planetary embryos and planetesimals originating in the inner solar system (e.g., Morbidelli et al. 2000; Hartogh et al. 2011; Alexander et al. 2012).”

“it proceeds as in our Solar System ( Morbidelli et al., 2000; Levison et al., 2001).”

“Recent models (24, 28, 74) propose that the Earth accreted from small and highly reduced materials (ΔIW −5) during the first stages of its formation (60 to 70% of its mass), then from larger and more oxidized bodies (ΔIW −2) toward the end of accretion.”

“…four main hypotheses (Drake and Righter, 2002): (cid:1) The planetesimals from which Earth accreted were essentially dry, and most of the volatiles were brought in during the Hadean epoch (the late veneer) via volatile-rich carbonaceous chondrite meteorites ( e.g., Morbidelli et al., 2000).”

“Thus, given the larger amount of water on Earth it is believed that one or more mechanisms contributed delivering a major part of its water (e.g. Morbidelli et al. 2000; Raymond et al. 2004, 2007a; Izidoro et al. 2013; O’Brien et al. 2014; Raymond and Izidoro 2017a).”

“However, as suggested by Quintana et al. (2002), the secondary star may prevent the initial delivery of volatiles to terrestrial planets from further out in the planetary system (as envisioned by Morbidelli et al. 2000 and Robert 2001).”

“…that is in the habitable zone, however, will not necessarily have surface water because of the vagaries of water delivery during planet formation (Morbidelli et al. 2000) and poorly understood processes that determine the distribution of water between the surface and the mantle (Cowan & Abbot…”

“[13] Current modelling of planetary formation predicts that terrestrial precursors originated from a variety of heliocentric distances and that the Earth was built from the accretion of this odd assortment [Morbidelli et al., 2000].”

“h uncertain by a factor of ˘5), suggesting that the planetesimals in its neighborhood were mostly dry and that water was delivered only by the small amount of planetesimals accreted from farther out (Morbidelli et al., 2000; Raymond et al., 2004; O’Brien et al., 2014). The very dry enstatite chondrites have been propo…”

“5 AU were the source of Earth’s water (Morbidelli et al., 2000).”

“They may also have been an important source of water for the protoEarth (e.g., Chyba and Sagan, 1992; Morbidelli et al., 2000; Marty, 2012; Trigo-Rodriguez and Martin-Torres, 2012).”

“…(Muralidharan et al. 2008; King et al. 2010; Machida & Abe 2010), chemical reactions between nebula gas and silicate melts (Sasaki 1990; Ikoma & Genda 2006), and delivery via ice-bearing bodies from the outer orbital region (Morbidelli et al. 2000; Raymond et al. 2007; Walsh et al. 2011).”

“ic distance of the comet r. According to figure 1 generated from equation 2, we note that the activity begins to be significative toward the sun around 2.7 au wich is the snow line of the Solar System ([1, 11]). According to [12], the activity of 67P/C-G began before the snow line but was very weak and not enough strong…”

“Modelling has shown that gravitational disturbances by the giant planets probably caused the outer asteroid belt, home to most asteroids of carbonaceous chondritic character, to lose the bulk of its mass towards the end of planetary formation, and it is thus likely that most bodies striking the Earth at this late stag…”

“The main belt, located beyond the water snowline at 2.7 AU (e.g., Abe et al. 2000), is thought to have profoundly impacted water delivery onto Earth (e.g., Morbidelli et al. 2000).”

“The inner asteroids, closest to Earth, are water devoid, while outside a radius of about 2.7 au the asteroids are icy C-class objects (e.g. Abe et al. 2000; Morbidelli et al. 2000).”

“…inventory could have been supplied by the accretion of icy objects either from the outer asteroid belt or from more distant regions of the solar system that were scattered onto Earth-impacting orbits (e.g., Morbidelli et al. 2000; Raymond et al. 2004; O’Brien et al. 2006; Raymond & Izidoro 2017).”

“…models also support the late delivery of material coming from the outer solar system due to the inward and outward migrations of Jupiter and Saturn, scattering some asteroids or planetesimals to the terrestrial planets (e.g., Morbidelli et al., 2000; O’Brien et al., 2014; Walsh et al., 2011).”

“For the Sun it is expected that in the early phases of the proto-planetary disk the temperature at the location which eventually becomes the HZ was initially too high for the condensation of water (e.g. Morbidelli et al., 2000).”

“…of water was brought to Earth at later times through cometary impacts compared to being accreted during the formation of the planet itself (e.g., Morbidelli et al. 2000; Raymond et al. 2004) and whether water undergoes signficant processing in warm regions of protostellar envelopes or disks…”

“The authors consider the scenario in which the bulk of the water provided to the Earth is sourced by a small number of collisions between the Earth and planet-sized embryos, rich in water, sourced from the asteroid belt (Morbidelli et al., 2000).”

“The delivery of volatiles from further out in the proto-planetary disk seems to be a natural outcome of planet formation (Morbidelli et al. 2000; Raymond et al. 2004).”

“Icy planetesimals, comets, and/or icy pebbles coming from outside the H2O snowline may bring water to rocky planets including the Earth (e.g., Morbidelli et al. 2000, 2012; Caselli & Ceccarelli 2012; van Dishoeck et al. 2014; Matsumura et al. 2016; Sato et al. 2016).”

“These discoveriessupport the suggestion that at least some of Earth’s current supply of water wasdelivered by asteroids some time following the collision that produced the Moon (Morbidelli et al. 2000, Lunine 2006).”

“Water arrived from the latestage accretion of planetesimals and dust—present models suggest ca 90% from asteroidal materials and ca 10% from comets (Morbidelli et al. 2000).”

“Indeed, such an effect has been enhanced if Jupiter migrated inward in the early stage of Earth’s formation [Walsh et al., 2011].”

“The onset melting temperatures (solidus) of the lower mantle materials, including peridotite, chondrite, natural mid-oceanic ridge basalt (Morbidelli et al., 2000), and pyrolite, have been compared to the temperature of the core at the pressure conditions of the CMB (Figure 7; Andrault et al.,…”

“In a scenario where the majority of these volatiles is delivered by only a relatively small number of large impactors (Morbidelli et al 2000), hit-and-run can play a decisive role, because it is a frequent outcome in such similar-sized collisions (∼ 50%; Kokubo and Genda 2010; Genda et al 2017).”

“…in the dynamical shaping of the Asteroid belt (Walsh et al. 2011; Morbidelli et al. 2010), and to their migratory dance toward and away from the Sun as the cause of a late delivery of volatile material to the inner rocky planets (Horner & Jones 2010; Morbidelli et al. 2000; Owen & Bar-Nun 1995).”

“mets (Halley, Hale-Bopp, and Hayakutake) all have been measured to have a D/H ratio twice the value of the ocean water. Several papers have summarised the D/H problematics; e.g. Robert et al. (2000), Morbidelli et al. (2000), Delsemme (1999, 2006). We will therefore here only very shortly summarise the relevant number…”

“Models show that Earth could have received its current volatile inventory via incorporation of planetesimals formed in the outer Solar System and gravitationally perturbed inward (Morbidelli et al., 2000; Raymond et al., 2004).”

“Such a dichotomy between Earth’s mantle and atmosphere leaves little space for a genetic link between the two reservoirs and an exotic origin of the progenitor of atmospheric Xe has often been advocated (e.g. Swindle and Kring, 1997; Morbidelli et al., 2000; Dauphas, 2003; Raymond et al., 2004; Marty and Meibom, 2007;…”

“The degree of radial mixing deter- mines each planet’s feeding zone, and the feeding zone is the most important factor in determining each planet’s composition (e.g., Morbidelli et al 2000; Raymond et al 2007a, b; Izidoro et al 2013; 2014).”

“In the classical model of in situ terrestrial planet formation in the solar system, water is delivered to Earth from primitive C-type asteroidal material (Morbidelli et al. 2000; Raymond et al. 2004, 2007a, 2013).”

“…on dry silicate grains in the protosolar nebula (Stimpfl et al. 2004), delivery through asteroids, comets, planetary embryos, and planetesimals (Morbidelli et al. 2000; O’Brien et al. 2006; Raymond et al. 2004, 2006, 2009; Lunine et al. 2003; Drake & Campins 2006), and water production through…”

“A majority of terrestrial water may have been carried by a few planetary embryos from the outer asteroid belt, which then combined to form the Earth during the final stages of planetary accretion [6].”

“Of the total iron mass present in the Earth, metallic Fe in the core is thought to represent 87%, whereas Fe in the mantle and crust is only 13% (McDonough 2000), some of which is also metal.”

“It is a modern concept based on orbital dynamics and on D/H ratios across the solar system that water was added to the surface from the outer solar system (Morbidelli et al., 2000).”

“If the gap was of secondary origin and cleared by a planet on an orbit at 73 au, some of the planetesimals would get scattered inwards where they could deliver volatiles such as water to inner planets that potentially formed dry (e.g. like Earth, Morbidelli et al. 2000).”

“the primordial delivery of water to the terrestrial planets [52,95,96,101].”

“C1143(A), and at the University of Hawai‘i 2.2-m telescope, Mauna Kea, Hawai‘i, USA. envelope and oxides in a magma ocean Genda & Ikoma (2007, 2008), or (iii) delivery by volatile-rich planetesimals (asteroids or comets) formed beyond the snow line (Morbidelli et al. 2000).”

“In our model, we have assumed that Ceres has an average bulk density of ∼2206 kg m−3 (Carry et al. 2008) and a global ice content of ∼ 10% (Morbidelli et al. 2000).”

“In the Solar System, evidence from the asteroid belt suggests a “canonical” snow-line distance of around 2.7AU (Abe et al. 2000; Morbidelli et al. 2000; Rivkin et al. 2002).”