
==== Front
Commun Earth Environ
Commun Earth Environ
Communications Earth & Environment
2662-4435
Nature Publishing Group UK London

1551
10.1038/s43247-024-01551-z
Article
A lunar core dynamo limited to the Moon’s first ~140 million years
http://orcid.org/0000-0001-7460-8957
Zhou Tinghong 1
http://orcid.org/0000-0002-0490-0124
Tarduno John A. john.tarduno@rochester.edu

123
http://orcid.org/0000-0003-4174-6389
Cottrell Rory D. 1
http://orcid.org/0000-0003-0705-3490
Neal Clive R. 4
http://orcid.org/0000-0003-3573-5915
Nimmo Francis 5
http://orcid.org/0000-0002-9405-8435
Blackman Eric G. 23
http://orcid.org/0000-0002-7839-2425
Ibañez-Mejia Mauricio 6
1 https://ror.org/022kthw22 grid.16416.34 0000 0004 1936 9174 Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY 14627 USA
2 https://ror.org/022kthw22 grid.16416.34 0000 0004 1936 9174 Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 USA
3 https://ror.org/022kthw22 grid.16416.34 0000 0004 1936 9174 Laboratory for Laser Energetics, University of Rochester, Rochester, NY 14623 USA
4 https://ror.org/00mkhxb43 grid.131063.6 0000 0001 2168 0066 Department of Civil Engineering and Geological Sciences, University of Notre Dame, Notre Dame, IN 46556 USA
5 grid.205975.c 0000 0001 0740 6917 Department of Earth and Planetary Sciences, University of California, Santa Cruz, CA 95064 USA
6 https://ror.org/03m2x1q45 grid.134563.6 0000 0001 2168 186X Department of Geosciences, University of Arizona, Tucson, AZ 85721 USA
6 9 2024
6 9 2024
2024
5 1 45627 1 2024
2 7 2024
© The Author(s) 2024
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Single crystal paleointensity (SCP) reveals that the Moon lacked a long-lived core dynamo, though mysteries remain. An episodic dynamo, seemingly recorded by some Apollo basalts, is temporally and energetically problematic. We evaluate this enigma through study of ~3.7 billion-year-old (Ga) Apollo basalts 70035 and 75035. Whole rock analyses show unrealistically high nominal magnetizations, whereas SCP indicate null fields, illustrating that the former do not record an episodic dynamo. However, deep crustal magnetic anomalies might record an early lunar dynamo. SCP studies of 3.97 Ga Apollo breccia 61016 and 4.36 Ga ferroan anorthosite 60025 also yield null values, constraining any core dynamo to the Moon’s first 140 million years. These findings suggest that traces of Earth’s Hadean atmosphere, transferred to the Moon lacking a magnetosphere, could be trapped in the buried lunar regolith, presenting an exceptional target for future exploration.

Single-crystal paleointensity measurements of Apollo samples suggest that if the Moon’s core produced a magnetic field, it disappeared by 4.36 billion years ago, possibly allowing a record of Earth’s Hadean atmosphere to be preserved in the lunar regolith.

Subject terms

Rings and moons
Core processes
Early solar system
Palaeomagnetism
Atmospheric chemistry
100000001 National Science Foundation (NSF) EAR1656348 100000104 National Aeronautics and Space Administration (NASA) 80NSSC19K0510 issue-copyright-statement© Springer Nature Limited 2024
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pmcIntroduction

A new interpretation of lunar magnetism calls for the lack of a long-lived magnetic field of internal origin for most of the Moon’s history1. Prior models had evoked a past long-lived lunar dynamo, producing a surface field at times as strong or stronger than Earth’s field2 and spanning some 2 billion years3. These conclusions, based on whole rock paleointensity (WRP) studies of Apollo samples, are paradoxical. The lunar core lacked sufficient energy to produce such a sustained field4, and time-correlative strong, long wavelength lunar magnetic crustal anomalies5 that should result from the long-lived dynamo are missing. The veracity of the magnetic data from prior analyses of Apollo samples had long been questioned6, but only recently has evidence arisen for the absence of a long-lived dynamo1.

The new data come from single crystal paleointensity (SCP)7 analyses of Apollo samples. Lunar whole rock samples have notoriously poor magnetic recording properties6. By measuring single silicate crystals rather than whole rocks, specimens with ideal single-domain-like magnetic minerals can be isolated8, meeting requirements for robust field recording9. SCP measurements of feldspars and pyroxene crystals from mare basalts 12053, 12040, 12021, 71055, and 14053, ranging in age from 3.2 to 3.9 Ga, yield null magnetizations1. Moreover, cooling experiments in known fields demonstrated that the crystals could have recorded magnetic fields with high efficiency if they had been present. These data thus define a Moon without a long-lived dynamo, with salient implications for future exploration. For example, the corresponding absence of a long-lived lunar paleomagnetosphere heightens the possibility that components of Earth’s Archean atmosphere were transported to the Moon via the geomagnetosphere, and could be preserved in buried lunar regoliths1,10. The intensity of early solar wind and the close proximity of the Moon to Earth increases the likelihood of this terrestrial-lunar transfer1,11,12.

With the insight provided by the SCP values indicating null values, some WRP data using thermal and nonthermal measurements are compatible with zero ambient fields1. However, the origin of Earth-like, or stronger, field strengths reported from other Apollo WRP studies2 using nonthermal methods remains a mystery. Compression of the solar wind by impacts generally produces amplifications too small to account for the nominal Apollo WRP values13,14. Impact charge separation can create fields thousands of microTeslas15–17. Magnetic minerals in whole rock cooling through their Curie temperature could be magnetized by such impact plasmas1. But it is unlikely that all the Apollo samples recording high apparent fields2 were cooling through the Curie temperatures of their respective magnetic minerals at the time of impacts2. This suggests another magnetization mechanism and/or that nonthermal techniques may not always be accurate6,9.

We note that the apparent Earth-like WRP values between ~3.9 and ~3.6 Ga, sometimes called the “high field epoch”3, have further motivated a model for an episodic lunar dynamo18. Evans and Tikoo18 suggested that downwelling diapirs could locally increase core-mantle boundary heat flow, providing enough power to drive a core dynamo that could create a 50 μT lunar surface field for a total duration of 400 kyr. But this duration represents only 0.13% of the hypothesized high field epoch. Lunar rocks having high magnetizations imparted by this episodic dynamo would thus be rare, conflicting with their relatively common occurrence in the Apollo collection. Thus, an episodic dynamo explanation, whether by diapirs or impact-stirring of the core18,19, exacerbates rather than solves the mystery of the high field values.

In contrast to the problematic long-lived or episodic dynamo hypotheses, satellite magnetic data suggest the Moon could have had a core dynamo in its very early history5. Weak magnetic anomalies of ~1 nT at 30 km altitude are particularly well-documented in the south polar region of the Moon20, and are possibly representative of large areas (but not all) of the deep lunar crust5. However, the exact age of such a potential dynamo is unknown. We address both the origin of high apparent paleofields from WRP analyses and the age of any early lunar core dynamo through new analyses of Apollo samples.

Results

~3.7 Ga Apollo high-Ti basalts

To investigate the origin of the high apparent paleofield values, we select two Apollo mare basalts for paired SCP and WRP analysis. We investigate Apollo 17 7003521,22, a high-Ti mare basalt with several Rb-Sr23,24 and Ar-Ar age analyses25. We recalculate the Rb-Sr isochrons using the latest 87Rb decay constant calibration relative to the U-Pb system26. The new Rb-Sr isochrons (Supplementary Fig. 1) are 3812 ± 118 Ma for the data of Evensen et al.23 and 3736 ± 114 Ma for that of Nyquist et al.24. Stettler et al.25 measured two separate aliquots of 70035 for Ar-Ar. Using decay constants of Renne et al.27 results in ages of 3656 ± 60 Ma and 3686 ± 51 Ma. Combining the four dates yields a weighted mean average of 3692 ± 34 Ma. The MSWD of 2.1 indicates the four values are in agreement within uncertainty.

We also investigate Apollo 17 75035, a high-Ti basalt21 also the subject of prior geochronological studies28,29, which we recalculate using recent decay constant and flux monitor data. The new Rb-Sr isochron using data of Murthy et al.29 (Supplementary Fig. 1) yields 3818 ± 127 Ma. Recalculation of Ar-Ar whole rock data of Turner and Cadogan28 yields 3734 ± 50 Ma, 3739 ± 40 Ma, and 3741 ± 40 Ma measured on plagioclase. The four ages yield a mean of 3741 ± 24 Ma. The MSWD of 0.5 again indicates agreement within uncertainty for all ages available from this sample.

High-Ti basalts 70035, 75035, SCP results

We find that the natural remanent magnetizations (NRMs) of 70035 feldspar crystals are extremely weak, suggesting that their magnetic minerals cooled in the absence of a magnetic field (“Methods” section). After heating to 590 °C, a considerable portion of lunar magnetic carriers should remain blocked1 and a magnetization should be observed if the feldspars had cooled in the presence of a lunar magnetic field. However, after demagnetization at 590 °C we find a magnetization indistinguishable from zero. Given this null magnetization state, the standard Thellier paleointensity approach is meaningless. Instead, we assess whether the crystals can record a magnetic field in accordance with magnetization theory9 by the following procedure1 (“Methods” section) (Fig. 1). First, we impart a partial thermoremanent magnetization (pTRM) at 590 °C in the presence of a 20 μT field. The sample is then demagnetized by heating to 590 °C, and the magnetization assessed to determine whether it returned to the null magnetization state. Next, a pTRM is imparted in a 40 μT field. The magnetizations of the two field strength pTRMs allow a determination of the recording efficiency1. We find the 70035 feldspars pass alteration checks (“Methods” section) have high efficiencies (103%; 96%, Fig. 1, Supplementary Fig. 2) and can record dynamo fields, but instead, they record zero magnetization levels. As a final check of the magnetization recording fidelity, we conduct scanning electron microscopy (SEM) and electron energy dispersive spectroscopy (EDS) analyses on the exact crystals used for SCP measurements (Fig. 1). These analyses confirm that the crystals contain magnetic carriers with single-domain-like (SD) and/or single vortex (SV) grain sizes. Specifically, these include isolated Fe particles (Fig. 1e, Supplementary Fig. 3a–c h–j, l, m), Fe-Ti grains (Supplementary Fig. 3a, d), and Fe grains adjacent to Fe-S (Supplementary Fig. 3e–g).Fig. 1 Images and TRM experiment of Apollo sample 70035.

a Transmission light microscopy photo. b Reflected light image. c SEM backscatter (20 keV) image. Red box indicates the location of the analysis area (d, e). d EDS data with analysis spot highlighted by red dot in (e). e SEM backscatter (20 keV) image of particle analyzed with elements identified highlighted. f TRM experiment on the crystal imaged in (a–e). Intensity versus experiment steps. Efficiency is calculated from the field-on intensities of applied fields of 20 μT and 40 μT.

The NRM of feldspars from 75035 also pass alteration checks and are essentially zero, where applied field experiments indicate the capability of the crystals to acquire fields with high efficiency (95%; 71%) (Fig. 2, Supplementary Fig. 2). SEM and EDS analyses further confirm the presence of minute inclusions within the size range of ideal magnetic recorders, namely SD-like or SV. These include Fe-Ti particles (Fig. 2e, Supplementary Fig. 4a, c, h, l) isolated Fe particles (Supplementary Fig. 4a, b), and Fe adjacent to minor Fe-S (Supplementary Fig. 4e–g).Fig. 2 Images and TRM experiment of Apollo sample 75035.

a Transmission light microscopy photo. b Reflected light image. c SEM backscatter (20 keV) image. Red box indicates the location of the analysis area (d, e). d EDS data with analysis spot highlighted by red dot in (e). e SEM backscatter (20 keV) image of particle analyzed with elements identified highlighted. f TRM experiment on the crystal imaged in (a–e). Intensity versus experiment steps. Efficiency is calculated from the field-on intensities of applied fields of 20 μT and 40 μT.

High-Ti basalts 70035, 75035, WRP results

Specimens from our 70035 sample show an irregular but a systematic demagnetization pattern after smoothing (Fig. 3a, Supplementary Fig. 5, “Methods” section). We use the REM’ nonthermal technique (See “Methods” section for definition), applying and subsequently demagnetizing a saturation remanent magnetization (Fig. 3b, c), to estimate the paleofield strength. For one specimen, the component structure is complex; while a high coercivity direction can be isolated, the demagnetization of the saturation remanence is irregular, precluding a paleointensity estimate (Supplementary Fig. 5). For another, however (Fig. 3a–c), a distinct component can be isolated between 10 and 40 mT and this yields a nominal paleofield of 15.9 ± 2.8 μT.Fig. 3 REM’ experiment for whole rock subsamples from Apollo samples 70035 and 75035.

a Orthogonal vector plot of AF demagnetization of NRM for 70035,4e (inset picture). The data presented are after two successive 3-point moving averages (“Methods” section). Demagnetization steps labeled in gray. Blue circles, horizontal projection; red squares, vertical projection; green arrows, vector corresponding to demagnetization range used in the paleointensity fit. b Orthogonal vector plot of AF demagnetization of a saturation remanent magnetization after 2 successive steps of 3-point moving average smoothing. Symbols as in (a). c NRM versus saturation remanent magnetization (circles). Demagnetization range used to calculate nominal paleointensity shown in blue. d–f Analyses for 75035,49a following conventions on (a–c) above. g–i Analyses for 75035,49c following conventions on (a–c) above.

Similarly, demagnetization data for 75035 show systematic trends after smoothing to reduce noise. For one specimen, the REM’ data yield a nominal paleofield of 155.7 ± 31.7 μT isolated between 20 and 50 mT (Fig. 3d, “Methods” section). There is some nonlinearity in the saturation remanent demagnetization curve (Fig. 3e), possibly indicating a net magnetic anisotropy, motivating a consideration of additional specimens from 75035 (Fig. 3g–i). Another specimen again yielded systematic changes indicating multiple components of magnetization, with less nonlinearity displayed in the demagnetization of the saturation remanent magnetization curve (Fig. 3g–i). A very high coercivity component was isolated for this specimen between 100 and 120 mT which yields a nominal paleointensity of 259.9 ± 77.4 μT.

For completeness, we have conducted SEM analyses of the whole rock specimens used for the REM’ paleointensity experiments. We find these contain relatively large (often 10 μm) multidomain (MD) Fe grains (Fig. 4), which are nonideal carriers.Fig. 4 Scanning electron microscope images and EDS analyses for whole rock subsamples from Apollo samples 70035 and 75035 used for REM’ experiment.

a Left: backscatter image (20 keV) from 70035,4d with elements identified; right: EDS data with collection spot highlighted by the red dot. b Left: backscatter image (20 keV) from 75035,49a with elements identified; right: EDS data with collection spot highlighted by the red dot.

3.97 and 4.36 Ga Apollo feldspars

To further assess the age limits on any early lunar core dynamo, we analyze components of two Apollo 16 breccias. Apollo 16 61016 is a dimict breccia with a reported U, Pu-136Xe age30 of 3.97 ± 0.25 Ga. We also analyze Apollo 16 60025, a ferroan anorthosite with an age of 4360 ± 3 Ma based on 207Pb-206Pb, 147Sm-143Nd, and 146Sm-142Nd isotopic systems31.

Dimict breccia 61016

We analyzed ~0.5 mm crystals of plagioclase (maskelynite). The NRM values are quite weak and after heating to 590 °C are weaker still, consistent with a null magnetization (Fig. 5, Supplementary Fig. 6). TRM experiments in two different fields pass alteration tests and show that the crystals have the ability to record the field at high efficiency (97%; 91%). SEM and EDS analyses show the presence of Fe particles (Fig. 5e, Supplementary Fig. 7a, b, d, e, g, h) and Fe-Ti grains (Supplementary Fig. 7j–m) within the size range of ideal SD/SV recorders (Fig. 5).Fig. 5 Images and TRM experiment of Apollo sample 61016.

a Transmission light microscopy photo. b Reflected light image. c SEM backscatter (15 keV) image. Red box indicates the location of the analysis area (d, e). d EDS data with analysis spot highlighted by red dot in (e). e SEM backscatter (15 keV) image of particle analyzed with elements identified highlighted. f TRM experiment on the crystal imaged in (a–e). Intensity versus experiment steps. Efficiency is calculated from the field-on intensities of applied fields of 20 μT and 40 μT.

Ferroan anorthosite 60025

We find that the NRM of feldspars from Apollo 60025 are extremely weak, both NRM values and after heating to 590 °C, consistent with null magnetizations (Fig. 6). Applied TRMs (“Methods” section) again pass alteration checks (Fig. 6, Supplementary Fig. 6). Efficiencies are somewhat less than in the Apollo basalts or dimict breccia (87%; 66%) but still high enough to record ambient magnetic fields had they been present. This lower efficiency may be related to the composition of the carriers which are Fe-Ti (Fig. 6e, Supplementary Fig. 8a, b, e–g, h, i, l, m), Fe with Mg (Supplementary Fig. 8h, j) or Fe with both Mg and Ti (Supplementary Fig. 8a, c). The sizes and shapes, however, are consistent with SD/SV magnetic recording properties able to record paleofields for billions of years.Fig. 6 Images and TRM experiment of Apollo sample 60025.

a Transmission light microscopy photo. b Reflected light image. c SEM backscatter (20 keV) image. Red box indicates the location of the analysis area (d, e). d EDS data with analysis spot highlighted by red dot in (e). e SEM backscatter (20 keV) image of particle analyzed with elements identified highlighted. f TRM experiment on the crystal imaged in (a–e). Intensity versus experiment steps. Efficiency is calculated from the field-on intensities of applied fields of 20 μT and 40 μT.

Discussion

Our new results from 3.7 Ga high-Ti basalts 70035 and 75035 shed light on both the origin of apparent Earth-like magnetizations recorded by some Apollo whole rock samples2 and the proposed, but temporally paradoxical, transient lunar dynamo18. The single silicate crystals from these basalts have magnetic inclusions with sizes consistent with ideal magnetic recording properties. These crystals also show high recording efficiencies, but record null ambient fields. In contrast, the bulk rocks contain nonideal MD magnetic particles, and yield strong yet variable magnetizations using nonthermal techniques (Fig. 7). A similar finding results from a comparison of SCP and WRP results for ~3.9 Ga Apollo 14 low-Ti/high-Al basalt 1405332. Single plagioclase and pyroxene yielded null magnetizations1, whereby WRP analyses (discussed in ref. 1) yielded 20 μT using the nonthermal REM’ method.Fig. 7 Summary lunar magnetization and impact history.

a History after ref. 1 with new SCP values (light blue diamonds). Dark blue diamonds are other SCP values and values from glass (64455) from ref. 1. Black symbols are WRP data consistent with zero or impact magnetization (15498). Grey circles are WRP values using nonthermal techniques. Impactor radius after ref. 15 and crustal impact saturation from ref. 41, 42. b Expanded view of new data. Open rectangles are WRP values from nonthermal methods. Value for 14053 is from ref. 34. Data from 75035 and 70035 are reported here. Data for 75035 have been slightly offset to show individual ranges.

There are two reasons the WRP values may not be recording the true paleointensity values. First, nonthermal paleointensity methods may not yield reliable paleointensity data in these lunar whole rocks because they contain complex MD magnetic particles. Nonthermal techniques sometimes yield erroneous high values when applied to terrestrial basalts of known age33. The reason why nonthermal methods yield correct values on some terrestrial basalts but not others is unknown. But one common factor between the terrestrial and lunar basalts is the presence of nonideal MD magnetic particles. It is also possible that the more reduced composition of lunar magnetic carriers relative to those in terrestrial rocks may exacerbate anomalous response by MD grains in nonthermal paleointensity approaches. A second explanation relates to impacts. After rock crystallization, an impact can impart a shock remanent magnetization (SRM) with the magnetic field supplied by the attendant magnetized plasma15–17. The SRM would be preferentially recorded by the whole rock samples because the relatively large MD magnetic grains they host have domain walls that can move by shock, resulting in a net magnetization9. In contrast, the smaller SD-like magnetic grains in the single feldspar crystals would have higher coercivities and would be less likely to be magnetized by shock, preserving the true null field state during their cooling. SRM’s have been considered previously34, especially for 14053. The magnetizing fields are well within the range of impact plasmas and the charge-separation process15–17. We note that the explanations of the high apparent magnetizations from whole rocks are not mutually exclusive for explaining the entire record of magnetizations reported from Apollo samples.

The proposed episodic lunar magnetic field relies on the interpretation that high apparent WRP values2 require a core dynamo2,3,18. Our observations indicate that the apparent high WRP values, whether they be nonthermal measurement artifacts or measures of shock and plasma fields, are not records of lunar core dynamo fields. Therefore, we conclude there is no reliable evidence for an episodic lunar dynamo from Apollo rocks.

The Moon lacks a magnetic field today, and therefore the null hypothesis is that it lacked one in the past, consistent with the limited energy to drive a dynamo in the relatively very small lunar core. Our new data do not reject this null hypothesis and instead further delineate the timeline of zero field measurements that provide evidence for the absence of a long-lived lunar dynamo (Fig. 7, “Methods” section, Supplementary Table 1). The observation of a null magnetization from Apollo 61016 indicates not only the lack of a dynamo at 3.97 Ga, but that any impact plasma magnetization had decayed before the sample cooled. The ultrafine magnetic minerals in the 61016 maskelynite also do not carry any subsequent shock magnetization, consistent with our results from 70035 to 75035.

The 4.36 Ga age of 60025 is ~100 million years older than the oldest age tentatively assigned to South Pole Aiken (SPA)35 but the SPA age remains uncertain. Multiple hypotheses have been put forth to explain the formation of SPA36 and its crustal anomalies37, and until the age of SPA is better constrained we cannot determine whether these formed before or after the shutdown of a hypothetical early dynamo constrained by the 60025 SCP data.

Our data at 4.36 Ga sets a youngest bound on the age of a hypothetical early lunar dynamo. The oldest bound would be set by the formation age of the Moon itself, and for this, there remains debate. Representing this uncertainty, Halliday and Canup38 bounded the lunar formation at 70–120 million years after the age of the Solar System, set at 4.5673 Ga. This suggests that a hypothetical dynamo could have been active in the first 87–137 million years after the formation of the Moon. A slightly older bound on the formation of the Moon is provided by the two-stage Hf-W model of core formation in Earth of 4.533 Ga, which provides the earliest time at which core formation in Earth can have ceased39. Since the last core formation event on Earth is thought to have been triggered by the Moon-forming impact, this model age also provides the earliest time at which the Moon can have formed. This yields a slightly longer duration of 170 million years for the hypothetical dynamo. But W isotope measurements of lunar samples suggest lunar differentiation occurred later than ~70 million years after the formation of the Solar System38,40. Therefore, we prefer a ~140 million years as the current best estimate of the upper bound on the duration of a hypothetical early dynamo.

This finding has importance for the nature of the lunar core and crust. The deep crustal anomalies seen on the Moon hint at an internal magnetization process5. The short duration of any dynamo could help explain why these weak anomalies are not seen everywhere on the Moon. Magmatic intrusions after the shutoff of any dynamo could reset previously magnetized crust. We suggest that any further exploration for a past lunar dynamo using rock samples should concentrate on this early lunar history. Because of the impact saturation of the crust1,41,42, this record may only be retrievable from drilling or by analyzing samples exposed by impact excavation. Key questions that could be addressed are whether paleointensities are consistent with an early thermally or procession-driven dynamo43,44 and, if present, how long this dynamo really lasted.

In the case of a precession-driven dynamo prior to 4.36 Ga, this mechanism only becomes important at a Moon-Earth separation >26–29 Earth radii (R⊕)43, and shuts off at ~48 R⊕. Outwards migration to >26–29 R⊕ takes less than 100 Myr in most models45, but the model time to reach 48 R⊕ is typically of the order of 1 Gyr43. If a precession-driven dynamo is responsible for the early lunar magnetic field, it implies sustained, rapid outward migration of the Moon. Alternatively, simple thermally-driven dynamos have little difficulty in sustaining a magnetic field for 140 Myr.46

Our findings are especially important for future exploration and studies of the lunar regolith. Without a long-lasting lunar paleomagnetosphere, solar wind volatiles can be implanted, and ancient regolith should contain relatively high abundances of 3He and other resources1,47. Today, elements from Earth’s atmosphere are transported to the lunar surface when the Moon passes through the Earth’s magnetosphere (magnetotail)48 because of the lack of a lunar magnetosphere. The preferential occurrence of hematite on the lunar nearside and inferences on ancient oxygen transport to the Moon from Earth’s atmosphere after the Great Oxidation Event (ca. 2.4 Ga)49 are consistent with our findings. Transport might have been even more effective in the ancient Moon because of the smaller Moon-Earth separation44. Solar winds associated with the rapidly rotating young Sun were intense during the early Solar System12, aiding the transport of Earth’s early atmosphere to the Moon. Our new data suggest the lack of a lunar magnetosphere extended back in time before 4.0 Ga, and thus transport through a terrestrial magnetosphere could have occurred during the Hadean Eon of Earth50–52. The early composition of the terrestrial atmosphere, and the question over the balance of gasses that promoted greenhouse warming to avoid complete freezing over of the planet given the faint young Sun12,53, remains a grand challenge question for terrestrial planet evolution. Recovery of older regolith (drilling, or sampling of impact crater walls) and return to Earth for analysis would be a pathway to obtaining geochemical data constraining Earth’s Hadean atmosphere and tackling this grand challenge question.

Methods

We separate single silicate crystals (feldspar) using non-magnetic tools for SCP analyses7,8. Silicate crystals analyzed in this investigation are approximately 0.5 mm in size. Bulk rock samples analyzed are approximate 3 mm in size.

Remanences are measured in the University of Rochester’s magnetically shielded room (ambient field <200 nT). We use the ultra-sensitive WSGI 3-component DC SQUID magnetometer for single crystal remanence measurement and the 2G SQUID magnetometer for whole rock remanence measurement. For nonheating methods we use REM’, (or ratio of equivalent magnetizations using derivatives), following ref. 54. REM’ is calculated over a given AF demagnetization range as the derivative of NRM demagnetization relative to isothermal remanent magnetization demagnetization. A saturation remanent magnetization was applied using a 3 T field. To address the possibility of gyroremanence during AF demagnetizations, we follow the protocol presented by Finn and Coe55. Progressive AF demagnetization is accomplished by permuting the direction in which gyroremanence may be acquired. A three-step running mean for orthogonal components is used to calculate directions.

For thermal experiments, we use CO2 laser techniques56 which afford heating times more than an order of magnitude shorter than standard paleomagnetic ovens. Samples are heated and cooled rapidly in air; a controlled (reducing) atmosphere is not used because this can promote further reduction and the formation of new magnetic particles1,57 (Supplementary Discussion).

TRM analyses follow that described in Tarduno et al.1. Repeat measurements are performed at every step. A zero magnetization is assigned if the nominal weak magnetization measured above the WSGI 3-component DC SQUID magnetometer’s threshold yields inconsistent directions between multiple measurements. Alteration checks are performed following Tarduno et al.50 and Tarduno et al.1. The difference between the field-off steps before and after the first field-on step is used to check for the presence of multidomain grains and potential alteration during heating. The linearity of TRM acquisition, interpreted as a measure of recording efficiency, is defined as M590,40μT/(M590,20μT × 2) × 100%, where M590,40μT and M590,20μT are the magnetizations imparted applied fields of 40 and 20 μT, respectively. We use non-magnetic materials, documented in multiple laboratories51, to mount crystals. We investigate magnetic mineralogy using a Zeiss Auriga scanning electron microscope (SEM) with an energy dispersive x-ray analysis (EDS) at the University of Rochester Integrated Nanosystems Center. Weight percentage estimates from EDS data are used to identify Fe-Ti grains that differ from ilmenite.

In addition to age recalibrations for Apollo samples 70035 and 75035, we recalibrate ages for Apollo samples yielding SCP data reported in Tarduno et al.1 using updated decay constants (see Supplementary Table 1).

Supplementary information

Transparent Peer Review file

Supplemental Material

Supplementary information

The online version contains supplementary material available at 10.1038/s43247-024-01551-z.

Acknowledgements

We thank G. Kloc for sample preparation and Sean O’Neil for electron microscopy analyses. We thank K. Lawrence for the sample selection. This work was supported by NSF grant EAR1656348 and NASA grant 80NSSC19K0510 (to J.A.T.).

Author contributions

J.A.T. conceived and supervised the project; T.Z. conducted SEM and nonthermal paleointensity analyses. R.D.C. conducted thermal paleointensity analyses. SEM and paleointensity data were analyzed by T.Z., R.D.C., and J.A.T. M.I.-M. contributed recalibration of radiometric ages, C.R.N. petrologic context, and F.N. and E.B. on dynamo and impact implications, respectively. J.A.T. and T.Z. wrote the manuscript with contributions for all the authors.

Peer review

Peer review information

Communications Earth & Environment thanks Ramon Egli and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: Joe Aslin. A peer review file is available.

Data availability

Data presented in this paper are available at the following link: 10.6084/m9.figshare.24639291.

Competing interests

The authors declare no competing interests.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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References

1. Tarduno JA Absence of a long-lived lunar paleomagnetosphere Sci. Adv. 2021 7 eabi7647 10.1126/sciadv.abi7647 34348904
Tarduno, J. A. et al. Absence of a long-lived lunar paleomagnetosphere. Sci. Adv. 7, eabi7647 (2021).34348904 10.1126/sciadv.abi7647
2. Cisowski SM Collinson DW Runcorn SK Stephenson A Fuller M A review of lunar paleointensity data and implications for the origin of lunar magnetism J. Geophys. Res. 1983 88 A691 A704
Cisowski, S. M., Collinson, D. W., Runcorn, S. K., Stephenson, A. & Fuller, M. A review of lunar paleointensity data and implications for the origin of lunar magnetism. J. Geophys. Res. 88, A691–A704 (1983).
3. Tikoo SM Suavet C Wang H Grove TL A two-billion-year history for the lunar dynamo Sci. Adv. 2017 3 e1700207 10.1126/sciadv.1700207 28808679
Tikoo, S. M., Suavet, C., Wang, H. & Grove, T. L. A two-billion-year history for the lunar dynamo. Sci. Adv. 3, e1700207 (2017).28808679 10.1126/sciadv.1700207
4. Evans AJ Tikoo SM Andrews-Hanna JC The case against an early lunar dynamo powered by core convection Geophys. Res. Lett. 2018 45 98 107 10.1002/2017GL075441
Evans, A. J., Tikoo, S. M. & Andrews-Hanna, J. C. The case against an early lunar dynamo powered by core convection. Geophys. Res. Lett. 45, 98–107 (2018).10.1002/2017GL075441
5. Wieczorek MA Strength, depth, and geometry of magnetic sources in the crust on the Moon from localized power spectrum analysis J. Geophys. Res. 2018 123 291 316 10.1002/2017JE005418
Wieczorek, M. A. Strength, depth, and geometry of magnetic sources in the crust on the Moon from localized power spectrum analysis. J. Geophys. Res. 123, 291–316 (2018).10.1002/2017JE005418
6. Lawrence K Johnson C L. Tauxe L Gee J Lunar paleointensity measurements: implications for lunar magnetic evolution Phys. Earth Planet. Inter. 2008 168 71 87 10.1016/j.pepi.2008.05.007
Lawrence, K., Johnson, C., L. Tauxe, L. & Gee, J. Lunar paleointensity measurements: implications for lunar magnetic evolution. Phys. Earth Planet. Inter. 168, 71–87 (2008).10.1016/j.pepi.2008.05.007
7. Tarduno JA Cottrell RD Smirnov AV The paleomagnetism of single silicate crystals: recording the geomagnetic field during mixed polarity intervals, superchrons and inner core growth Rev. Geophys. 2006 44 RG1002 10.1029/2005RG000189
Tarduno, J. A., Cottrell, R. D. & Smirnov, A. V. The paleomagnetism of single silicate crystals: recording the geomagnetic field during mixed polarity intervals, superchrons and inner core growth. Rev. Geophys. 44, RG1002 (2006).10.1029/2005RG000189
8. Tarduno JA Geodynamo history preserved in single silicate crystals: origins and long-term mantle control Elements 2009 5 217 222 10.2113/gselements.5.4.217
Tarduno, J. A. Geodynamo history preserved in single silicate crystals: origins and long-term mantle control. Elements 5, 217–222 (2009).10.2113/gselements.5.4.217
9. Dunlop, D. J. & Özdemir, Ö. Rock Magnetism: Fundamentals and Frontiers (Cambridge Univ. Press, 2001).
10. Fagents SA Rumpf ME Crawford IA Joy KH Preservation potential of implanted solar wind volatiles in lunar paleoregolith deposits buried by lava flows Icarus 2010 207 595 604 10.1016/j.icarus.2009.11.033
Fagents, S. A., Rumpf, M. E., Crawford, I. A. & Joy, K. H. Preservation potential of implanted solar wind volatiles in lunar paleoregolith deposits buried by lava flows. Icarus 207, 595–604 (2010).10.1016/j.icarus.2009.11.033
11. Tarduno JA Geodynamo, solar wind, and magnetopause 3.4 to 3.45 billion years ago Science 2010 327 1238 1240 10.1126/science.1183445 20203044
Tarduno, J. A. et al. Geodynamo, solar wind, and magnetopause 3.4 to 3.45 billion years ago. Science 327, 1238–1240 (2010).20203044 10.1126/science.1183445
12. Tarduno JA Blackman EG Mamajek EE Detecting the oldest geodynamo and attendant shielding from the solar wind: implications for habitability Phys. Earth Planet. Inter. 2014 233 68 87 10.1016/j.pepi.2014.05.007
Tarduno, J. A., Blackman, E. G. & Mamajek, E. E. Detecting the oldest geodynamo and attendant shielding from the solar wind: implications for habitability. Phys. Earth Planet. Inter. 233, 68–87 (2014).10.1016/j.pepi.2014.05.007
13. Hood LL Richmond NC Spudis PD Origin of strong lunar magnetic anomalies: Further mapping and examinations of LROC imagery in regions antipodal to young large impact basins J. Geophys. Res. 2013 118 1265 1284 10.1002/jgre.20078
Hood, L. L., Richmond, N. C. & Spudis, P. D. Origin of strong lunar magnetic anomalies: Further mapping and examinations of LROC imagery in regions antipodal to young large impact basins. J. Geophys. Res. 118, 1265–1284 (2013).10.1002/jgre.20078
14. Oran R Weiss BP Shprits Y Miljković K Tóth G Was the moon magnetized by impact plasmas? Sci. Adv. 2020 6 eabb1475 10.1126/sciadv.abb1475 33008909
Oran, R., Weiss, B. P., Shprits, Y., Miljković, K. & Tóth, G. Was the moon magnetized by impact plasmas? Sci. Adv. 6, eabb1475 (2020).33008909 10.1126/sciadv.abb1475
15. Crawford DA Schultz PH Laboratory observations of impact-generated magnetic fields Nature 1988 336 50 52 10.1038/336050a0
Crawford, D. A. & Schultz, P. H. Laboratory observations of impact-generated magnetic fields. Nature 336, 50–52 (1988).10.1038/336050a0
16. Bruck Syal M Schultz PH Cometary impact effects at the Moon: Implications for lunar swirl formation Icarus 2015 257 194 206 10.1016/j.icarus.2015.05.005
Bruck Syal, M. & Schultz, P. H. Cometary impact effects at the Moon: Implications for lunar swirl formation. Icarus 257, 194–206 (2015).10.1016/j.icarus.2015.05.005
17. Crawford DA Simulations of magnetic fields produced by asteroid impact: Possible implications for planetary paleomagnetism Int. J. Impact Engng. 2020 137 103464 10.1016/j.ijimpeng.2019.103464
Crawford, D. A. Simulations of magnetic fields produced by asteroid impact: Possible implications for planetary paleomagnetism. Int. J. Impact Engng. 137, 103464 (2020).10.1016/j.ijimpeng.2019.103464
18. Evans AJ Tikoo SM An episodic high-intensity lunar core dynamo Nat. Astron. 2022 6 325 330 10.1038/s41550-021-01574-y
Evans, A. J. & Tikoo, S. M. An episodic high-intensity lunar core dynamo. Nat. Astron. 6, 325–330 (2022).10.1038/s41550-021-01574-y
19. Le Bars M Wieczorek MA Karatekin Ö Cébron D Laneuville M An impact-driven dynamo for the early Moon Nature 2011 479 215 10.1038/nature10565 22071767
Le Bars, M., Wieczorek, M. A., Karatekin, Ö., Cébron, D. & Laneuville, M. An impact-driven dynamo for the early Moon. Nature 479, 215 (2011).22071767 10.1038/nature10565
20. Hood LL Bryant I van der Leeuw J Lunar magnetic anomalies and polar ice Geophys. Res. Lett. 2022 49 e2022GL100557 10.1029/2022GL100557
Hood, L. L., Bryant, I. & van der Leeuw, J. Lunar magnetic anomalies and polar ice. Geophys. Res. Lett. 49, e2022GL100557 (2022).10.1029/2022GL100557
21. Paces JB A strontium and neodymium isotopic study of Apollo 17 high-Ti mare basalts: resolution of ages, evolution of magmas, and origins of source heterogeneities Geochim. Cosmochim. Acta 1991 55 2025 2043 10.1016/0016-7037(91)90040-C
Paces, J. B. et al. A strontium and neodymium isotopic study of Apollo 17 high-Ti mare basalts: resolution of ages, evolution of magmas, and origins of source heterogeneities. Geochim. Cosmochim. Acta 55, 2025–2043 (1991).10.1016/0016-7037(91)90040-C
22. Neal, C. R. A new look at Apollo 17 basaltic samples 45 years on. In 49th Lunar and Planetary Science Conference (Lunar Planetary Institute, 2018).
23. Evensen NM Murthy VR Coscio Jr MR Rb-Sr ages of some mare basalts and the isotopic and trace element systematics in lunar fines Proc. 4th Lunar Sci. Conf. 1973 4 1707 1724
Evensen, N. M., Murthy, V. R. & Coscio Jr, M. R. Rb-Sr ages of some mare basalts and the isotopic and trace element systematics in lunar fines. Proc. 4th Lunar Sci. Conf. 4, 1707–1724 (1973).
24. Nyquist, L. E., Bansal, B. M., Wiesmann, H. & Jahn, B.-M. Taurus-Littrow chronology: some constraints on early lunar crustal development. Proc. 5th Lunar Sci. Conf. 5, 15l5–1539 (1974).
25. Stettler, A., Eberhardt, P., Geiss, J., Grögler, N. & Maurer, P. 39Ar-40Ar ages and 37Ar-38Ar exposure ages of lunar rocks. Proc. 4th Lunar Sci. Conf. 4, 1865–1888 (1973).
26. Nebel O Scherer EE Mezger K Evaluation of the 87Rb decay constant by age comparison against the U-Pb system Earth Planet. Sci. Lett. 2011 301 1 8 10.1016/j.epsl.2010.11.004
Nebel, O., Scherer, E. E. & Mezger, K. Evaluation of the 87Rb decay constant by age comparison against the U-Pb system. Earth Planet. Sci. Lett. 301, 1–8 (2011).10.1016/j.epsl.2010.11.004
27. Renne PR Balco G Ludwig KR Mundil R Min K Response to the comment by W.H. Schwarz et al. on “Joint determination of 40K decay constants and 40Ar*/40K for the Fish Canyon sanidine standard, and improved accuracy for 40Ar/39Ar geochronology” by P.R. Renne et al. (2010) Geochim. Cosmochim. Acta 2011 75 5097 5100 10.1016/j.gca.2011.06.021
Renne, P. R., Balco, G., Ludwig, K. R., Mundil, R. & Min, K. Response to the comment by W.H. Schwarz et al. on “Joint determination of 40K decay constants and 40Ar*/40K for the Fish Canyon sanidine standard, and improved accuracy for 40Ar/39Ar geochronology” by P.R. Renne et al. (2010). Geochim. Cosmochim. Acta 75, 5097–5100 (2011).10.1016/j.gca.2011.06.021
28. Turner, G. & Cadogen, P. H. The history of lunar bombardment inferred from 40Ar-39Ar dating of highland rocks. Proc. 6th Lunar Sci. Conf. 6, 1509–1538 (1975).
29. Murthy, V. R. & Coscio Jr, M. R., Rb-Sr ages and isotopic systematics of some Serenitatis mare basalts. Proc. 7th Lunar Sci. Conf. 7, 1529–1544 (1976).
30. Eugster O Chronology of dimict breccias and the age of South Ray crater at the Apollo 16 site Meteor. Planet. Sci. 1999 34 385 391 10.1111/j.1945-5100.1999.tb01347.x
Eugster, O. Chronology of dimict breccias and the age of South Ray crater at the Apollo 16 site. Meteor. Planet. Sci. 34, 385–391 (1999).10.1111/j.1945-5100.1999.tb01347.x
31. Borg LE Connelly JN Boyet M Carlson RW Chronological evidence that the Moon is either young or did not have a global magma ocean Nature 2011 477 70 72 10.1038/nature10328 21849974
Borg, L. E., Connelly, J. N., Boyet, M. & Carlson, R. W. Chronological evidence that the Moon is either young or did not have a global magma ocean. Nature 477, 70–72 (2011).21849974 10.1038/nature10328
32. Snape JF The timing of basaltic volcanism at the Apollo landing sites Geochim. Cosmochim. Acta 2019 266 29 53 10.1016/j.gca.2019.07.042
Snape, J. F. et al. The timing of basaltic volcanism at the Apollo landing sites. Geochim. Cosmochim. Acta 266, 29–53 (2019).10.1016/j.gca.2019.07.042
33. Muxworthy AR Heslop D Paterson GA Michalk D A Preisach method for estimating absolute paleofield intensity under the constraint of using only isothermal measurements: 2. Experimental testing J. Geophys. Res. 2011 116 B04103
Muxworthy, A. R., Heslop, D., Paterson, G. A. & Michalk, D. A Preisach method for estimating absolute paleofield intensity under the constraint of using only isothermal measurements: 2. Experimental testing. J. Geophys. Res. 116, B04103 (2011).
34. Cournéde C Gattacceca J Rochette P Magnetic study of large Apollo samples: possible evidence for an ancient centered dipolar field on the Moon Earth Planet. Sci. Lett. 2012 331-332 31 42 10.1016/j.epsl.2012.03.004
Cournéde, C., Gattacceca, J. & Rochette, P. Magnetic study of large Apollo samples: possible evidence for an ancient centered dipolar field on the Moon. Earth Planet. Sci. Lett. 331-332, 31–42 (2012).10.1016/j.epsl.2012.03.004
35. Garrick-Bethell I Troctolite 76535: a sample of the Moon’s South Pole-Aitken basin? Icarus 2020 338 113430 10.1016/j.icarus.2019.113430
Garrick-Bethell, I. et al. Troctolite 76535: a sample of the Moon’s South Pole-Aitken basin? Icarus 338, 113430 (2020).10.1016/j.icarus.2019.113430
36. Zhang N Lunar compositional asymmetry explained by mantle overturn following the South Pole-Aitken impact Nat. Geosci. 2022 15 37 41 10.1038/s41561-021-00872-4
Zhang, N. et al. Lunar compositional asymmetry explained by mantle overturn following the South Pole-Aitken impact. Nat. Geosci. 15, 37–41 (2022).10.1038/s41561-021-00872-4
37. Wieczorek MA Weiss BP Stewart ST An impactor origin for lunar magnetic anomalies Science 2012 335 1212 1215 10.1126/science.1214773 22403388
Wieczorek, M. A., Weiss, B. P. & Stewart, S. T. An impactor origin for lunar magnetic anomalies. Science 335, 1212–1215 (2012).22403388 10.1126/science.1214773
38. Halliday AN Canup RM The accretion of planet Earth Nat. Rev. Earth Environ. 2023 4 19 35 10.1038/s43017-022-00370-0
Halliday, A. N. & Canup, R. M. The accretion of planet Earth. Nat. Rev. Earth Environ. 4, 19–35 (2023).10.1038/s43017-022-00370-0
39. Kleine T Walker RJ Tungsten isotopes in planets Ann. Rev. Earth Planet. Sci. 2017 45 389 417 10.1146/annurev-earth-063016-020037 30842690
Kleine, T. & Walker, R. J. Tungsten isotopes in planets. Ann. Rev. Earth Planet. Sci. 45, 389–417 (2017).30842690 10.1146/annurev-earth-063016-020037
40. Kruijer TS Kleine T Tungsten isotopes and the origin of the Moon Earth Planet. Sci. Lett. 2017 475 15 24 10.1016/j.epsl.2017.07.021
Kruijer, T. S. & Kleine, T. Tungsten isotopes and the origin of the Moon. Earth Planet. Sci. Lett. 475, 15–24 (2017).10.1016/j.epsl.2017.07.021
41. Neukum G Ivanov BA Hartmann WK Cratering records in the inner solar system in relation to the lunar reference system Space Sci. Rev. 2001 96 55 86 10.1023/A:1011989004263
Neukum, G., Ivanov, B. A. & Hartmann, W. K. Cratering records in the inner solar system in relation to the lunar reference system. Space Sci. Rev. 96, 55–86 (2001).10.1023/A:1011989004263
42. Stöffler D Ryder G Stratigraphy and isotope ages of lunar geologic units: chronological standard for the inner Solar System Space Sci. Rev. 2001 96 9 54 10.1023/A:1011937020193
Stöffler, D. & Ryder, G. Stratigraphy and isotope ages of lunar geologic units: chronological standard for the inner Solar System. Space Sci. Rev. 96, 9–54 (2001).10.1023/A:1011937020193
43. Dwyer CA Stevenson DJ Nimmo F A long-lived lunar dynamo driven by continuous mechanical stirring Nature 2011 479 212-214 10.1038/nature10564 22071766
Dwyer, C. A., Stevenson, D. J. & Nimmo, F. A long-lived lunar dynamo driven by continuous mechanical stirring. Nature 479, 212-214 (2011).22071766 10.1038/nature10564
44. Meyer J Wisdom J Precession of the lunar core Icarus 2011 211 921 924 10.1016/j.icarus.2010.09.016
Meyer, J. & Wisdom, J. Precession of the lunar core. Icarus 211, 921–924 (2011).10.1016/j.icarus.2010.09.016
45. Korenaga J Rapid solidification of Earth’s magma ocean limits early lunar recession Icarus 2023 400 115564 10.1016/j.icarus.2023.115564
Korenaga, J. Rapid solidification of Earth’s magma ocean limits early lunar recession. Icarus 400, 115564 (2023).10.1016/j.icarus.2023.115564
46. Laneuville M Wieczorek MA Breuer D Tosi N Asymmetric thermal evolution of the Moon J. Geophys. Res. 2013 118 1435 1452 10.1002/jgre.20103
Laneuville, M., Wieczorek, M. A., Breuer, D. & Tosi, N. Asymmetric thermal evolution of the Moon. J. Geophys. Res. 118, 1435–1452 (2013).10.1002/jgre.20103
47. Fa W Jin Y-Q Quantitative estimation of helium-3 spatial distribution in the lunar regolith layer Icarus 2007 190 15 23 10.1016/j.icarus.2007.03.014
Fa, W. & Jin, Y.-Q. Quantitative estimation of helium-3 spatial distribution in the lunar regolith layer. Icarus 190, 15–23 (2007).10.1016/j.icarus.2007.03.014
48. Terada K Biogenic oxygen from Earth transported to the Moon by a wind of magnetospheric ions Nat. Astron. 2017 1 0026 10.1038/s41550-016-0026
Terada, K. et al. Biogenic oxygen from Earth transported to the Moon by a wind of magnetospheric ions. Nat. Astron. 1, 0026 (2017).10.1038/s41550-016-0026
49. Li S Widespread hematite at high latitudes of the Moon Sci. Adv. 2020 6 eaba1940 10.1126/sciadv.aba1940 32917587
Li, S. et al. Widespread hematite at high latitudes of the Moon. Sci. Adv. 6, eaba1940 (2020).32917587 10.1126/sciadv.aba1940
50. Tarduno JA Cottrell RD Davis WJ Nimmo F Bono RK A Hadean to Paleoarchean geodynamo recorded by single zircon crystals Science 2015 349 521 524 10.1126/science.aaa9114 26228145
Tarduno, J. A., Cottrell, R. D., Davis, W. J., Nimmo, F. & Bono, R. K. A Hadean to Paleoarchean geodynamo recorded by single zircon crystals. Science 349, 521–524 (2015).26228145 10.1126/science.aaa9114
51. Tarduno JA Paleomagnetism indicates that primary magnetite in zircon records a strong Hadean geodynamo Proc Natl. Acad. Sci. USA 2020 117 2309 2319 10.1073/pnas.1916553117 31964848
Tarduno, J. A. et al. Paleomagnetism indicates that primary magnetite in zircon records a strong Hadean geodynamo. Proc Natl. Acad. Sci. USA 117, 2309–2319 (2020).31964848 10.1073/pnas.1916553117
52. Tarduno JA Hadaean to Palaeoarchaean stagnant-lid tectonics revealed by zircon magnetism Nature 2023 618 531 536 10.1038/s41586-023-06024-5 37316722
Tarduno, J. A. et al. Hadaean to Palaeoarchaean stagnant-lid tectonics revealed by zircon magnetism. Nature 618, 531–536 (2023).37316722 10.1038/s41586-023-06024-5
53. Shaw GH Earth’s atmosphere - Hadean to early Proterozoic Chemie Der Erde-Geochem. 2008 68 235 264 10.1016/j.chemer.2008.05.001
Shaw, G. H. Earth’s atmosphere - Hadean to early Proterozoic. Chemie Der Erde-Geochem. 68, 235–264 (2008).10.1016/j.chemer.2008.05.001
54. Gattacceca J Rochette P Toward a robust normalized magnetic paleointensity method applied to meteorites Earth Planet. Sci. Lett. 2004 227 377 393 10.1016/j.epsl.2004.09.013
Gattacceca, J. & Rochette, P. Toward a robust normalized magnetic paleointensity method applied to meteorites. Earth Planet. Sci. Lett. 227, 377–393 (2004).10.1016/j.epsl.2004.09.013
55. Finn DR Coe RS A new protocol for three-axis static alternating field demagnetization of rocks Geochem. Geophys. Geosyst. 2016 17 1815 1822 10.1002/2015GC006178
Finn, D. R. & Coe, R. S. A new protocol for three-axis static alternating field demagnetization of rocks. Geochem. Geophys. Geosyst. 17, 1815–1822 (2016).10.1002/2015GC006178
56. Tarduno JA Cottrell RD Watkeys MK Bauch D Geomagnetic field strength 3.2 billion years ago recorded by single silicate crystals Nature 2007 446 657 660 10.1038/nature05667 17410173
Tarduno, J. A., Cottrell, R. D., Watkeys, M. K. & Bauch, D. Geomagnetic field strength 3.2 billion years ago recorded by single silicate crystals. Nature 446, 657–660 (2007).17410173 10.1038/nature05667
57. Papike, J. & Taylor, L., Simon, S. Lunar minerals. In Lunar Source Book (eds Heiken, G. H., Vaniman, D. T., French, B. M.) Ch 5, 137–153 (Cambridge Univ. Press, 1991).
