Temporally distributed parent body accretion in the C reservoir of the solar system

TL;DR

This paper models the timing of parent body accretion in the C reservoir of the solar system, revealing a wide range of formation times from less than 1 million to about 4 million years after solar system formation, with implications for planetary evolution.

Contribution

It provides the first evidence for temporally distributed accretion of C reservoir parent bodies, linking formation times to degrees of alteration and differentiation.

Findings

CR parent bodies accreted from <1 Ma to ~4 Ma after CAIs.

Accretion times inversely correlate with meteorite alteration.

Differentiated and undifferentiated C reservoir bodies formed over overlapping times.

Abstract

Accretion processes in protoplanetary disks produce a diversity of small bodies that played a crucial role in multiple reshuffling events throughout the solar system and in both early and late accretion of planets. Application of thermo-chronometers to meteorites provides precise dating of the formation age of mineralogical components. Nucleosynthetic anomalies indicating a dichotomy between NC and C meteorites and precise parent body (PB) chronology can be combined with thermal evolution models to constrain the timescale of accretion and dynamical processes in the early solar system. Achondrite PBs are considered to have accreted early and mostly in the NC region, while late accretion in the C region produced mostly undifferentiated PBs, such as the CR chondrite PB that formed as late as 4 Ma after CAIs. However, presence of more evolved CR-related meteorites suggests also an earlier accretion timing. We present modeling evidence for a temporally distributed accretion of parent bodies of CR-related meteorite groups that originate from a C reservoir and range from aqueously altered chondrites to partially differentiated primitive achondrites. The PB formation times derived range from <1 Ma to ~4 Ma after solar system formation, with ~3.7 Ma, ~1.5-2.75 Ma, <~0.6 Ma, and <~0.7 Ma for CR, Flensburg, NWA 6704, and NWA 011. This implies that accretion processes in the C reservoir started as early as in the NC reservoir and produced differentiated PBs with carbonaceous compositions in addition to undifferentiated C chondritic PBs. The accretion times correlate inversely with the degree of the meteorites' alteration, metamorphism, or differentiation. Accretion times for CI/CM, Ryugu, and Tafassites PBs of ~3.75 Ma, ~1-3 Ma, and 1.1 Ma, respectively, fit well into this correlation in agreement with the thermal and alteration conditions suggested by the meteorites.

Tables

Table 1. Table 1 : Time (in Ma rel. to CAIs) and temperature (in K) data used for fitting the CR-related meteorite parent bodies. The data for water-rich CI and CM chondrites and for CR-related Tafassites are shown as well. Notes: ( b ) b {}^{(\text{b})} breunnerite, ( c ) c {}^{(\text{c})} calcite, ( d ) d {}^{(\text{d})} dolomite, ( p ) p {}^{(\text{p})} phosphate, ( pl ) pl {}^{(\text{pl})} plagioclase, ( px ) px {}^{(\text{px})} pyroxene, ( w ) w {}^{(\text{w})} whole-rock, ( ol ) ol {}^{(\text{ol})} olivine, ( ca ) ca {}^{(\text{ca})} carbonates. The age data are from 38 (CR1-3), 29 (Flensburg), 32 (NWA 011 and NWA 2976), 2 , 34 (NWA 4587), 1 , 33 (NWA 6704), 2 (NWA 10132), 32 , 17 (Tafassites), 38 , 30 (CI, CM). The closure temperatures are from 37 , 39 (CR1-3), 29 (Flensburg), 40 , 41 and 35 (NWA 011, NWA 2976, NWA 4587, NWA 6704, NWA 10132), 17 (Tafassites), 30 (CI, CM). A CAI age of 4567.9 Ma was used.

Meteorite	Closure $T$		Closure $t$		Method
	$T^c$	${\sigma }_T$	$t^c$	${\sigma }_t$
	K	K	Ma	Ma
Aqueously altered CR1-3
Renazzo ${}^{\left(\text{d}\right)}$	344.5	16.5	4.8	+4.24/-2.4	Mn-Cr
Renazzo ${}^{\left(\text{c}\right)}$	344.5	16.5	4.55	+7.4/-2.8	Mn-Cr
GRO 95577 ${}^{\left(\text{c}\right)}$	308	25	12.57	+2.1/-1.4	Mn-Cr
Aqueously altered CI and CM
Orgueil, Ivuna, Y980115 (d)	398	50	5.485	0.655	Mn-Cr
Orgueil ${}^{\left(\text{b}\right)}$	398	50	9.7	3.6	Mn-Cr
Murchison, Y791198 (c)	318	50	5.445	0.655	Mn-Cr
Aqueously altered Flensburg
Flensburg ${}^{\left(\text{ca}\right)}$	423	50	3.4	1	Mn-Cr
Partially molten Tafassites (T6-7)
Tafassasset ${}^{\left(\text{w}\right)}$	1200	100	2.9	0.9	Hf-W
Tafassasset ${}^{\left(\text{w}\right)}$	950	100	4.9	0.3	Mn-Cr
Tafassasset ${}^{\left(\text{p}\right)}$	720	50	19.86	8.1	U/Pb-Pb
NWA 11561 ${}^{\left(\text{p}\right)}$	720	50	7.55	2.85	U/Pb-Pb
NWA 7317 ${}^{\left(\text{p}\right)}$	720	50	8.42	2.94	U/Pb-Pb
NWA 12455 ${}^{\left(\text{p}\right)}$	720	50	10.1	1.75	U/Pb-Pb
Differentiated CR-related grouplets
NWA 011 ${}^{\left(\text{pl, px}\right)}$	750	130	4.5	0.33	Al-Mg
NWA 011 ${}^{\left(\text{ol, px}\right)}$	850	100	5.62	2.64	Mn-Cr
NWA 2976 ${}^{\left(\text{w, pl, px}\right)}$	750	130	5.08	0.05	Al-Mg
NWA 2976 ${}^{\left(\text{pl, px}\right)}$	770	50	5.01	0.59	U/Pb-Pb
NWA 4587 ${}^{\left(\text{w, pl, px}\right)}$	750	130	4.68	0.04	Al-Mg
NWA 4587 ${}^{\left(\text{px}\right)}$	770	50	5.47	0.23	U/Pb-Pb
NWA 6704 ${}^{\left(\text{pl, px}\right)}$	750	130	5.31	0.13	Al-Mg
NWA 6704 ${}^{\left(\text{pl, px}\right)}$	850	100	6.24	0.81	Mn-Cr
NWA 6704 ${}^{\left(\text{px}\right)}$	770	50	5.14	+0.3/-0.22	U/Pb-Pb
NWA 10132 ${}^{\left(\text{pl, px, ol}\right)}$	750	130	5.42	0.7	Al-Mg
NWA 7680	850	100	5.53	0.34	Mn-Cr

Full text

1 One-Sentence Summary

Thermal evolution fits to the chronology of CR-related meteorites reveal accretion times of $<1$ to $4$ Ma in the outer solar system.

2 Highlights

• •

We fit thermal evolution models to the thermo-chronological data of CR-related meteorites CR1-3, NWA 011, NWA 6704, and Flensburg

• •

Our modeling suggests different parent bodies with different degrees of alteration, metamorphism, or differentiation

• •

Parent body accretion times derived range from $<1$ Ma to $\approx 4$ Ma after solar system formation, with $\approx 3.7$ Ma, $\approx 1.5-2.75$ Ma, $\lesssim 0.7$ Ma, and $\lesssim 0.6$ Ma for CR1-3, Flensburg, NWA 6704, and NWA 011, respectively

• •

Accretion processes in the C reservoir started as early as in the NC reservoir and produced differentiated parent bodies with carbonaceous compositions

• •

Accretion times of carbonaceous chondritic CI/CM, Ryugu, and Tafassites parent bodies fit well into the sequence derived

Keywords: Asteroids; Meteorites; Chronology; Accretion; Parent Bodies.

Introduction

Meteoritic components provide evidence for the isotopical heterogeneity of the early solar nebula and carry 16O excesses derived from nucleosynthesis or CO self shielding.27 Isotopic variations from inter-reservoir exchange give rise to linear mixing lines for different meteorite groups or clans in the oxygen three-isotope plot.3 The CR chondrites is a group of undifferentiated meteorites that includes two subgroups defined based on their degree of aqueous alteration (CR1-3) or thermal metamorphism and partial melting (initially classified as CR6-7). Their common origin indicated by oxygen isotope systematics (Fig. 1, top panels) is challenged by a striking contrast in the metamorphism and alteration degree that could indicate distinct evolution paths and parent bodies. The CR1-3 bulk oxygen isotope compositions form a unique mixing line27 that requires an anhydrous precursor different from CI and CM.42, 25 An oxygen isotopic heterogeneity43 and patterns similar to CM imply low-temperature aqueous alteration on an isotopically heterogeneous chondritic parent body (PB).27 The CR6-7 data are broadly similar to the CR1-3 mixing line, but give rise to a separate mixing line and were suggested to belong to the carbonaceous primitive achondrite group called Tafassites.17 Further meteorites with geochemical affinities to CR include the basaltic achondrite grouplets NWA 011,31 NWA 6704,1 and NWA 7680,2 other members of the Tafassites group,17 and, potentially, the chondrite Flensburg.29 Considered together with CR1-3, these meteorites are clearly distinct from other carbonaceous meteorites. Precursors of NWA 011, NWA 6704 and NWA 7680 grouplets are related to CR based on either indistinguishable or broadly similar oxygen isotope compositions. NWA 011, NWA 6704, and NWA 7680 are, further, related to CR based on the $\varepsilon^{54}Cr$ similarity2 that is close to the ordinary and enstatite chondrites for all other differentiated meteorites, but not for these grouplets (and Tafassites17). However, NWA 011 and its pairings likely do not originate from the same parent body as Tafassites, due to different FeO-Mn compositions and incompatible chemical composition, e.g., higher silicate FeO content and Ca-rich pyroxene unlikely to have formed from the same precursor. NWA 6704 grouplet’s $\Delta^{17}$O values suggest another separate parent body, supported, further, by its unique pyroxenitic lithology. The Flensburg bulk data plots in the transition field to CR chondrites with a marginal overlap.29

Therefore, the broad oxygen isotope composition similarity rather indicates that Tafassites, NWA 6704, NWA 011, NWA 7680, Flensburg, and CR chondrites derive from at least six different parent bodies. Here, we address four of those, while the Tafassites parent body was considered in 17 and not enough data is available for NWA 7680.

The genetic relationship of CR-related meteorites implies that they sourced from the same region and their oxygen systematics were produced by an isotopic exchange between 16O-rich solids and 16O-poor gases3. In general, the bulk O isotope compositions of the CR-related meteorites plot in a more 16O-rich region relative to water-rich carbonaceous CI, CM, Tagish Lake, and Flensburg meteorites (Fig. 1, top left panel). Similar $\delta^{18}$O and $\delta^{17}$O values imply that all CR-related groups are derived from a single homogeneous region of the solar nebula. This region contained more 16O-rich material than the Earth and CI chondrites based on the position below TFL. Lower $\delta^{18}$O values suggest, further, lower condensation or equilibration temperature for the precursor material than for that of CI and CM chondrites. Formation in the C reservoir beyond the orbit of Jupiter has been suggested for CR-related meteorites.44

The carbonate O isotopic data indicates partially similar carbonate formation conditions concerning temperature and oxygen fugacity and carbon source in CR1-3 chondrites as in CI, CM, and TL chondrites, but different to Flensburg (Fig. 1, top right panel). Both implications agree with roughly similar alteration temperatures for CR1-3, CI, CM, and TL, but a higher alteration temperature of Flensburg. The differences in $\Delta^{17}$O and $\delta^{18}$O values between the groups imply different alteration conditions, e.g., the duration, temperature, redox conditions, and fluid composition experienced.25

Meteorite nucleosynthetic anomalies distinguish two major groups of meteorites, NC and C (Fig. 1, bottom panel), and two major reservoirs of planetesimal formation separated early on in the protoplanetary disk. The meteorite Flensburg and CR-related groups and grouplets (CR, Tafassites, NWA 011, NWA 6704, and NWA 7680) have C-like nucleosynthetic anomalies. The CR-related meteorites plot closely to each other and to CH chondrites. All these meteorites are within the same region of the C meteorite composition. Their similar O isotopic composition and nucleosynthetic anomalies reflect a similar accreting material within a relatively confined region further out in the protoplanetary disk. More broadly, they reflect a similar material with other C meteorites, such as Flensburg, CI, CM, and with C-type NEAs like Ryugu and Bennu.

Data and methods:

Characteristic parent body properties were derived from the analysis of formation of various primary (olivine, pyroxene, plagioclase) or secondary (carbonates, such as calcite, dolomite, or breunnerite, formed in the presence of aqueous solutions) mineralogical components, or whole-rock samples (Table 1). Carbonates formed close to the peak of hydrothermal activity in the source regions of CR1-3 and Flensburg chondrites. Since they incorporate Mn, the short-lived decay system 53Mn-53Cr with a 53Mn half-life of $3.7$ million years is used to constrain their age. Data available for CR give rise to a Renazzo dolomite, a GRO 95577 calcite, and a Renazzo calcite data points. Calcite and dolomite formation in Flensburg has been dated with almost indistinguishable relative formation times that give rise to a single data point.29 In the heavily metamorphosed and partially molten T6-7 meteorites and differentiated CR-related NWA 011, NWA 6704, and NWA 7680 grouplets that lack carbonates, other components, such as whole-rock, olivine, pyroxene, plagioclase, and phosphates were dated with the U/Pb-Pb, Al-Mg, and Mn-Cr chronometers (Table 1). U/Pb-Pb phosphate data were derived recently,17 providing one data point for each of three North-West Africa Tafassites and Tafassasset in addition to previously available Hf-W and Mn-Cr data, while for the differentiated CR-related grouplets Al-Mg, Mn-Cr, or Pb-Pb data are available. Overall formation temperatures for all these components are bracketed by $\approx 300$ K and $\approx 1300$ K, and the ages available fall into the first $\approx 27$ Ma after the solar system formation (Table 1). Thus, the data describe the cooling behavior after reaching 26Al-induced temperature maxima at the burial depths of respective meteorites, except for Flensburg, where carbonates formed during the initial heating phase triggered by 26Al on the prograde branch of a temperature curve. 29 The carbonate ages in CI and CM meteorites fit to the above time scale 38 providing a possibility for a comparison of parent body aqueous alteration history.30

We used state-of-the-art global thermal evolution models for early solar system planetesimals. The numerical setup is described in detail in the Supplementary Material. The models included, metal-silicate separation in the case of NWA 011 and NWA 6704, as melting and (partial) differentiation are indicated by the meteorites. Properties of CR-related parent bodies were obtained by approximating the data points with the evolution of the temperature at different depths in the respective time interval using a root mean square (RMS) procedure and by comparing with the maximum metamorphic temperatures.45, 47, 46 By varying the radius $R$ over a wide range of $10$ km to $200$ km and the accretion time $t_{0}$ between [math] and $5$ Ma after CAIs, we constrain ranges within the $(R,t_{0})$-diagram appropriate for bodies that are likely to have produced various CR-related materials.

Results:

The fit quality calculated (Fig. 2) shows best-fit parent body accretion times and sizes. The absolute value of the optimal fit quality is case dependent, while, in general, best-fit objects are characterized by its minimum. A global minimum is difficult to obtain given that the number of data points available varies between $1$ and $6$ for different parent bodies. Thus, a minimum or best-fit field defined by a plateau of the fit quality and an acceptable fit quality defined by strong gradients around the boundaries of the plateau are more suitable than a global minimum. Conclusive constraints on the accretion time were obtained with overall uncertainties of $\lesssim 1$ Ma for each meteorite group, while the radius estimates are less ideal. For CR1-3, a field with a minimum fit quality $\chi_{n}\leq 0.15$ is obtained for an accretion between $3.7$ and $3.8$ Ma after CAIs (Fig. 2, top left panel). The corresponding radius spread is $30-200$ km, but a minimum of $0.12$ for $\chi_{n}$ is obtained at $t_{0}\approx 3.7$ Ma and $R=70-120$ km. For an acceptable fit quality of $\leq 0.5$, the accretion time is bracketed by $3.6$ and $4.1$ Ma. Overall, the best-fit accretion time of $3.7$ Ma is almost indistinguishable from the CR1-3 chondrule formation time of $\approx 3.6$ Ma.48

In the case of Flensburg, an acceptable $\chi_{n}\leq 0.5$ field is obtained between $t_{0}=2.5$ and $t_{0}=2.75$ Ma for any radius, but also for an accretion as early as $1.5$ Ma of bodies larger than $R=80$ km (Fig. 2, second row, left panel). Thus, no constraint on the radius can be derived from the fit procedure. The reason for that and for an acceptable fit quality for an early accretion is the availability of only one data point. For any object within the field with $\chi_{n}\leq 0.5$, a depth can be found at which the temperature curve crosses the center of the data point on the ascending branch. However, the earlier the accretion, the shallower this depth (down to $\lesssim 300$ m) and the higher the peak central temperature of the planetesimal, correlating inversely with the accretion time and exceeding the melting temperature in extreme cases. Thus, we consider planetesimals that accreted prior to $2.5$ Ma as less likely parent body candidates. Those that accreted between $2.5$ Ma and $2.75$ Ma have, by contrast, mostly homogeneous structures and thermal conditions throughout their interiors, in agreement with the prevalent notion of water-rich chondrite parent bodies. An accretion time of $\approx 2.7$ Ma fits the Flensburg carbonate data best for any parent body size.

The fit for the achondrites NWA 011, NWA 2976, and NWA 4587 (Fig. 2, third row, left panel) produced an acceptable fit quality of $\chi_{n}\leq 2.5$ for an accretion between [math] and $0.6$ Ma and radii of $>20$ km. A minimum field can hardly be identified, if at all, by $\chi_{n}\leq 2.2$ that does not affect the accretion time interval, but changes the radius estimate to $>40$ km. Relatively high fit quality values are rooted in a maximum time difference of $\approx 0.7$ Ma at the depth of NWA 4587, very small uncertainties of Al-Mg ages of $0.33$, $0.05$, and $0.04$ MA for NWA 011, NWA 2976, and NWA 4587, respectively, and a necessity to fit each of these data points along with the respective Mn-Cr or Pb-Pb data at the same depth for each meteorite.

Finally, the fit for the grouplet comprising NWA 6704 and NWA 10132 was done with four data points. The shapes of the $\chi_{n}$ isolines resemble those obtained for the NWA 011 grouplet, as it was expected by the relative similarity of the data. Models produced an acceptable fit quality of $\chi_{n}\leq 1.8$ for $t_{0}\lesssim 0.9$ Ma and $R>20$ km, and a plateau with $\chi_{n}\leq 1.5$ for an accretion before $0.7$ Ma and a radius of $>30$ km.

The right column of Fig. 2 shows temperature curves at burial depths of the meteorites from which the data were obtained within the representative best-fit parent bodies. The latter are indicated by red dots in the respective fit quality panels. For CR1-3 (top right panel), two depths corresponding to two meteorites Renazzo (5.2 km) and GRO 95577 (7.8 km) were calculated within an object with a radius of $90$ km. The temperature curves fit the Mn-Cr data very well and the maximum values of $370$ K or $395$ K agree with the temperature ranges suggested from lab work and with the petrologic type. A larger burial depth and a longer heating phase of GRO 95577 are in agreement with its high alteration degree compared to Renazzo and corroborate, further, the positions of these meteorites on the CR mixing line as a result of their alteration extents. From one data point available for Flensburg, only one burial depth within the parent body could be fitted (Fig. 2, second row, right panel). The temperature curve for the representative body with $R=20$ km crosses the Mn-Cr carbonate data point on its prograde branch in agreement with the data point reflecting the age of an early and prograde carbonate formation and the lack of carbonate forming fluids later on. A maximum temperature of $565$ K reached lies well within the interval of $470-670$ K suggested.29 In the case of NWA 011 grouplet (Fig. 2, third row, right panel), three meteorites with two data points each resulted in fits of three different burial depths within the parent bodies in the $\chi_{n}$ minimum field. Burial depths of $2.55$, $2.6$, and $3$ km within a body with $R=100$ km correlate with the decreasing Al-Mg age of the meteorites, reflecting stronger heating and slower cooling at higher depth. A burial depth difference of $\approx 50$ m for NWA 011 and NWA 4587 results from an Al-Mg age difference of only $0.18$ Ma. The maxima of the respective temperature curves of $1610-1630$ K are sufficient to produce basaltic melts consistent with the composition of the grouplet members and our model produced differentiated silicate material at the fit depth. However, depths of $2.3-3$ km within the sample parent body also implies an intrusive nature for these meteorites. For the NWA 6704 grouplet, fits of three NWA 6704 and one NWA 10132 data points produce typically two different depths. Both fits are dominated by the Al-Mg age difference of $0.1$ Ma that resulted in a burial depth difference of $\approx 50$ m. A deeper location for NWA 10132 with an younger Al-Mg age is consistent with slightly higher temperature maximum and slower cooling. Similarly to the NWA 011 grouplet, maximum temperatures of $1645-1648$ K agree with silicate melting, while the differentiated silicate material obtained with our model at the burial depths agrees with the meteorite composition. Burial depths of $\approx 3.3$ km imply an intrusive origin also for this grouplet.

Discussion

Our calculations indicate an origin on different parent bodies for the meteorite groups considered, with a parent body accretion time of $t_{0}\approx 3.7$ Ma and size of $R\approx 90$ km for the CR1-3, $t_{0}\approx 2.5-2.75$ Ma for Flensburg, $t_{0}\lesssim 0.6$ Ma and $R>40$ km for NWA 011 grouplet, and $t_{0}\lesssim 0.7$ Ma and $R>30$ km for NWA 011. This demonstrates a spread of formation times between [math] Ma and $4$ Ma after the formation of the solar system in the accretion disk region of carbonaceous chondrites. Accretion times we derived recently for other water-rich parent bodies, such as Tafassites ($1.1_{-0.4}^{+0.3}$ Ma),17 Ryugu ($1-3$ Ma),30 and a CM/CI asteroid ($\approx 3.8$ Ma)30 support this conclusion. Our results confirm, further, that rocky parent bodies accreted early and sequentially17 from $<1$ Ma to $4$ Ma after CAIs, and witnessed different accretion mechanisms within a limited region of the outer solar system. The CR1-3 parent body complements the CI/CM parent body with a considerably smaller radius of $R\approx 15-25$ km but a similar accretion time of $3.75-3.8$ Ma and a sub-10 km sized parent body of the NEA Ryugu that accreted between $1$ Ma and $3$ Ma suggested recently.30 Our results for the CR1-3 parent body and the Tafassites parent body model17 imply, further, that the meteorites classified initially as CR6-7 and re-classified as Tafassites do not belong to the same group as aqueously altered CR. An earlier formation of the NWA 011 and NWA 6704 grouplets’ parent bodies than that of the Tafassites is in an agreement with the former being differentiated and the latter only partially molten. The parent body size estimates are less conclusive due to the lack of data but they fall into the range of typical sizes estimated for early solar system planetesimals.50 Of note is a size contrast to the sub-10 km large parent body of Ryugu that was derived based on porosity modeling given lack of any chronological data in 2021.30

Two types of structures were obtained in the terms of metal-silicate differentiation. Parent bodies of CR1-3 and Flensburg are homogeneous with maximum temperatures remaining below the melting temperatures of metal or silicates. Internal heating by 26Al warmed large fractions of their volumes relatively uniformly, leaving a small volume of outer layer relatively cool, and supporting production of petrologic types 1-3 at different depths. These alteration conditions are similar to those of CI/CM PB,30 while bearing similarity to a lesser extent to the original parent body of Ryugu that was suggested to be heated to a higher temperature that enabled a partial dehydration.30, 49 In addition, peak central temperatures of up to $700$ K obtained for the favored Flensburg PB models also come close to those derived for Ryugu from a potential partial dehydration. While the CR1-3 carbonate ages are older than Flensburgs within the margin of error, an earlier accretion of the Flensburg asteroid than the CR1-3 PB derived confirms that it recorded the earliest fluid activity on a planetary object in the solar system.29 Initial Ryugu sample analysis indicates a close similarity to the CI material56, suggesting a potential origin on a common parent body. Ryugu samples originate from two different sites and have high porosities comparable with that derived by MASCOT that observed at yet another site. Thus, the asteroid is suggested to be homogeneous. However, an origin of high-porosity Ryugu material and low-porosity CI meteorites on a common parent body would require either a strong sorting of the rubble after parent body destruction, such that only high-porosity pieces would accrete to form Ryugu, but such a sorting appears unlikely. Or, it would require different impacts onto the parent body, of which one would be only shallow and eject enough material from a high-porosity surface layer to form Ryugu, and at least one other impact would eject CI material from deeper within where porosity has been reduced stronger.

An opposite differentiated structure type was produced due to partial melting in the interior of NWA 011 and NWA 6704 parent bodies. These structures are similar to those of primitive achondritic Acapulco-Lodran47 and Tafassites parent asteroids.17 They are, further, consistent with the accretion times calculated for them and reported for achondrite and primitive achondrites in the literature. Not much chondritic material with typical petrologicy types relative to the total parent body volume can be expected on these parent due to small burial depths for of overall $2.5-3.3$ km derived for the differentiated meteorites. By contrast, primitive achondritic and achondritic materials are abundant at these depths and further below. Any kind of chondritic material could be retained only in thin surface shells, while most of the parent body volume would be dominated by achondritic metal or silicate rocks. In particular, early accretion of the NWA 011 and NWA 6704 parent asteroids implies a similar magmatic evolution to Vesta that formed within $\lesssim 1$ Ma.53 Bearing similarities to eucrites and classified originally as a non-cumulate eucrite,52 NWA 011, and also NWA 6704 likely experienced similar petrogenesis. Given overall burial depths of $2.55-3.25$ km derived, both grouplets would be intrusive rocks and, in fact, NWA 011 has a cumulate-eucrite-like REE pattern,51 while NWA 6704 spectrum showed a close similarity to the basaltic and cumulate eucrites.54 The asteroid (34698) 2001 OD22 suggested as parent body of NWA 670455 does not fulfill the size requirements we derived and, if related, should be a piece of a fractured parent asteroid. A partially differentiated parent body with a radius of $\approx 200$ km has been proposed previously as parent body of CR1-3 and NWA 011 6, 7, 8. Our results contradict that, both due to a smaller best-fit CR1-3 parent body size and a substantial difference of its accretion to that of NWA 011 and NWA 6704. A lack of sufficiently large asteroids with exposed silicates that would meet compositional constraints of CR-related meteorites suggests that their parent bodies were removed from the asteroid belt or have experienced mantle removal and their cores are represented by metallic asteroids. The parent body of the presumably metallic asteroid (16) Psyche should have a radius of $\approx 200$ km, since Psyche’s mean radius is $\approx 110$ km, and would, therefore, lie in the best-fit fields for NWA 011 and NWA 6704. Regardless of parent body removal or loss of mantle, ejection of mantle portions by energetic collisions could have produced small basaltic meteorites present in the asteroid belt.

Accretion times of CR-related parent bodies including the result for Tafassites 17 with other water-rich parent bodies from the C reservoir, such as that of Ryugu and of CI/CM groups, are compared in Fig. 3. The emerged accretion trend is correlated with the petrologic type of the meteorites and the degree of metamorphism or melting in agreement with the control of the heating rate by the amount of 26Al incorporated. The result of a temporally distributed accretion of CR-related parent bodies implies that accretion processes in the C reservoir started as early as in the NC reservoir and produced differentiated parent bodies with carbonaceous chondritic compositions, along with a spectrum of petrographic types, compositions, and parent body structures. A confirmation of the Ryugu PB age and an addition of carbonaceous NEA formation times are expected from extensive Hayabusa2 and OSIRIS-REx sample analyses. Accretion in different parts of protoplanetary disks is observable by facilities such as ALMA, cosmochemical analyses of accretion processes are achievable using observations by VLT, while exoplanet search projects, such as PLATO and CHEOPS telescopes, can provide further clues via statistical information on the architecture of planetary systems.

3 Funding:

WN acknowledges support by the Deutsche Forschungsgemeinschaft (DFG, project number 434933764). MT and WN acknowledge support by Klaus Tschira Foundation.

4 Competing Interests:

None.

5 Data and Materials Availability:

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

6 Code Availability:

The numerical model used is described in detail in the Supplementary Information. The code is available only from the corresponding author upon reasonable request.

7 Supplementary Materials:

Supplementary materials are available as a separate pdf file.