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64-503: Evidence for the LHB derives from moon rock samples of Lunar craters brought back by the Apollo program astronauts . Isotopic dating showed that the rocks were last molten during impact events in a rather narrow interval of time, suggesting that a large proportion of craters were formed during this period. Several hypotheses attempt to explain this apparent spike in the flux of impactors in

128-451: A bull's-eye . A multi-ringed basin may have an area of many thousands of square kilometres. An impact crater of diameter bigger than about 180 miles (290 km) is referred to as a basin . In adjacent rings, the ratio of the diameters approximates √ 2 :1 ≈ 1.41 to 1. To start, a peak ring crater has A multi-ringed basin has an important difference, which is multiple peak-rings. In extremely large collisions, following

192-400: A crewed lunar program in the 1970s, but succeeded in landing three robotic Luna spacecraft with the capability to collect and return small samples to Earth. A combined total of less than half a kilogram of material was returned. In 1993, three small rock fragments from Luna 16 , weighing 200 mg, were sold for US$ 442,500 at Sotheby's (equivalent to $ 933,317 in 2023). In 2018,

256-441: A 2:1 orbital resonance , causing the eccentricities of their orbits to increase. The orbits of the planets become unstable and Uranus and Neptune are scattered onto wider orbits that disrupt the outer belt, causing a bombardment of comets as they enter planet-crossing orbits. Interactions between the objects and the planets also drive a faster migration of Jupiter and Saturn's orbits. This migration causes resonances to sweep through

320-774: A conundrum at the time. The LHB offers a potential explanation for this anomaly. Under this model, the rocks dating to 3.8 Ga solidified only after much of the crust was destroyed by the LHB. Collectively, the Acasta Gneiss in the North American cratonic shield and the gneisses within the Jack Hills portion of the Narryer Gneiss Terrane in Western Australia are the oldest continental fragments on Earth, yet they appear to post-date

384-825: A large negative europium anomaly . The type location is Mare Crisium sampled by Luna 24 . The main repository for the Apollo Moon rocks is the Lunar Sample Laboratory Facility at the Lyndon B. Johnson Space Center in Houston, Texas . For safekeeping, there is also a smaller collection stored at White Sands Test Facility in Las Cruces, New Mexico . Most of the rocks are stored in nitrogen to keep them free of moisture. They are handled only indirectly, using special tools. Some Moon rocks from

448-592: A mass less than half of Mars and originally orbited between Mars and the asteroid belt. Planet V's orbit became unstable due to perturbations from the other inner planets causing it to intersect the inner asteroid belt. After close encounters with Planet V, many asteroids entered Earth-crossing orbits, causing the Late Heavy Bombardment. Planet V was ultimately lost, likely plunging into the Sun. In numerical simulations, an uneven distribution of asteroids, with

512-432: A phenomenon, it is still controversial and based on debatable assumptions. Two criticisms are that (1) the "cluster" of impact ages could be an artifact of sampling a single basin's ejecta, and (2) that the lack of impact melt rocks older than about 4.1 Ga is related to all such samples having been pulverized, or their ages being reset. The first criticism concerns the origin of the impact melt rocks that were sampled at

576-515: A solar resonance when the Moon reached 27 Earth radii. Planetesimals left over from the formation of the terrestrial planets were shown to be depleted too rapidly due to collisions and ejections to form the last lunar basins. The long-term stability of primordial Earth or Venus co-orbitals (trojans or objects with horseshoe orbits) in conjunction with the lack of current observations indicate that they were unlikely to have been common enough to contribute to

640-474: A team at the University of Colorado at Boulder postulate that much of Earth's crust, and the microbes living in it, could have survived the bombardment. Their models suggest that although the surface of Earth would have been sterilized, hydrothermal vents below Earth's surface could have incubated life by providing a sanctuary for thermophile microbes . In April 2014, scientists reported finding evidence of

704-723: A total mass of over 1,090 kilograms (2,400 lb). Some were discovered by scientific teams (such as ANSMET ) searching for meteorites in Antarctica , with most of the remainder discovered by collectors in the desert regions of northern Africa and Oman . A Moon rock known as "NWA 12691", which weighs 13.5 kilograms (30 lb), was found in the Sahara Desert at the Algerian and Mauritanian borders in January 2017, and went on sale for $ 2.5 million in 2020. Rocks from

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768-493: A wood plaque which included the recipients' flag which had also flown aboard Apollo 17. Many of the presentation Moon rocks are now unaccounted for, having been stolen or lost . Three minerals were discovered from the Moon: armalcolite , tranquillityite , and pyroxferroite . Armalcolite was named for the three astronauts on the Apollo 11 mission: Arm strong , Al drin and Col lins . Because of their rarity on Earth and

832-405: Is a statistical artifact produced by sampling rocks scattered from a single large impact. A range of evidence suggests that there may instead have been a more extended period of lunar bombardment, lasting from approximately 4.2 billion years ago to 3.5 billion years ago. The main piece of evidence for a lunar cataclysm comes from the radiometric ages of impact melt rocks that were collected during

896-535: Is believed to be sent down from the heavens). Moon rocks collected during the course of lunar exploration are currently considered priceless. In 2002, a safe was stolen from the Lunar Sample Building that contained minute samples of lunar and Martian material . The samples were recovered, and NASA estimated their value during the ensuing court case at about $ 1 million for 10 oz (280 g) of material. Naturally transported Moon rocks in

960-444: Is impossible to obtain age determinations using standard radiometric methods. Scientists continue to study the bombardment history of the moon in an attempt to clarify the history of the inner solar system. If a cataclysmic cratering event truly occurred on the Moon, Earth would have been affected as well. Extrapolating lunar cratering rates to Earth at this time suggests that the following number of craters would have formed: Before

1024-508: Is often ejected following its encounter with Jupiter, leading some to propose that the Solar System began with five giant planets . Recent works, however, have found that impacts from this inner asteroid belt would be insufficient to explain the formation of ancient impact spherule beds and the lunar basins, and that the asteroid belt was probably not the source of the Late Heavy Bombardment. According to one planetesimal simulation of

1088-438: Is rock originating from Earth's Moon . This includes lunar material collected during the course of human exploration of the Moon , and rock that has been ejected naturally from the Moon's surface and landed on Earth as meteorites . Moon rocks on Earth come from four sources: those collected by six United States Apollo program crewed lunar landings from 1969 to 1972; those collected by three Soviet uncrewed Luna probes in

1152-673: The Moon . They named it the "lunar cataclysm" and proposed that it represented a dramatic increase in the rate of bombardment of the Moon around 3.9 Ga. If these impact melts were derived from these three basins, then not only did these three prominent impact basins form within a short interval of time, but so did many others based on stratigraphic grounds. At the time, the hypothesis was considered controversial. As more data has become available, particularly from lunar meteorites , this hypothesis, while still controversial, has become more popular. The lunar meteorites are thought to randomly sample

1216-469: The Slave Craton in northwestern Canada. Older rocks could be found, however, in the form of asteroid fragments that fall to Earth as meteorites . Like the rocks on Earth, asteroids also show a strong cutoff point, at about 4.6 Ga, which is assumed to be the time when the first solids formed in the protoplanetary disk around the then-young Sun. The Hadean, then, was the period of time between

1280-759: The oldest ages of rocks from the Earth are between 3.8 and 4.28 billion years. Moon rocks fall into two main categories: those found in the lunar highlands (terrae), and those in the maria . The terrae consist dominantly of mafic plutonic rocks. Regolith breccias with similar protoliths are also common. Mare basalts come in three distinct series in direct relation to their titanium content: high-Ti basalts , low-Ti basalts , and Very Low-Ti (VLT) basalts . Almost all lunar rocks are depleted in volatiles and are completely lacking in hydrated minerals common in Earth rocks. In some regards, lunar rocks are closely related to Earth's rocks in their isotopic composition of

1344-581: The "hellish" conditions assumed on Earth for the time, from the Greek Hades . Zircon dating suggested, albeit controversially, that the Hadean surface was solid, temperate, and covered by acidic oceans. This picture derives from the presence of particular isotopic ratios that suggest the action of water-based chemistry at some time before the formation of the oldest rocks (see Cool early Earth ). Of particular interest, Manfred Schidlowski argued in 1979 that

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1408-766: The 1970s; those collected by the Chinese Lunar Exploration Program 's uncrewed probes; and rocks that were ejected naturally from the lunar surface before falling to Earth as lunar meteorites . Six Apollo missions collected 2,200 samples of material weighing 381 kilograms (840 lb), processed into more than 110,000 individually cataloged samples. 21.55 kg (47.51 lb) 34.30 kg (75.62 lb) 42.80 kg (94.35 lb) 76.70 kg (169.10 lb) 95.20 kg (209.89 lb) 110.40 kg (243.40 lb) Three Luna spacecraft returned with 301 grams (10.6 oz) of samples. The Soviet Union abandoned its attempts at

1472-545: The Apollo landing sites. According to this alternative hypothesis, the cluster of impact melt ages near 3.9 Ga simply reflects material being collected from a single impact event, and not several. Additional criticism also argues that the age spike at 3.9 Ga identified in Ar/Ar dating could also be produced by an episodic early crust formation followed by partial Ar losses as the impact rate declined. A second criticism concerns

1536-514: The Apollo landing sites. While these impact melts have been commonly attributed to having been derived from the closest basin, it has been argued that a large portion of these might instead be derived from the Imbrium basin. The Imbrium impact basin is the youngest and largest of the multi-ring basins found on the central nearside of the Moon, and quantitative modeling shows that significant amounts of ejecta from this event should be present at all of

1600-723: The Apollo missions are displayed in museums, and a few allow visitors to touch them. One of these, called the Touch Rock , is displayed in the Smithsonian National Air and Space Museum in Washington, D.C. The idea of having touchable Moon rocks at a museum was suggested by Apollo scientist Farouk El-Baz , who was inspired by his childhood pilgrimage to Mecca where he touched the Black Stone (which in Islam

1664-597: The Apollo missions. The majority of these impact melts are thought to have formed during the collision of asteroids or comets tens of kilometres across, forming impact craters hundreds of kilometres in diameter. The Apollo 15 , 16 , and 17 landing sites were chosen as a result of their proximity to the Imbrium , Nectaris , and Serenitatis basins, respectively. The apparent clustering of ages of these impact melts, between about 3.8 and 4.1 Ga, led investigators to postulate that those ages record an intense bombardment of

1728-419: The Earth, large portions of the lunar crust appear to be composed of rocks with high concentrations of the mineral anorthite . The mare basalts have relatively high iron values. Furthermore, some of the mare basalts have very high levels of titanium (in the form of ilmenite ). Primary igneous rocks in the lunar highlands compose three distinct groups: the ferroan anorthosite suite, the magnesian suite, and

1792-466: The LHB. However, recent calculations of gas-flows combined with planetesimal runaway growth in the outer Solar System imply that Jovian planets formed extremely rapidly, on the order of 10 My, which does not support this explanation for the LHB. The Planet V hypothesis posits that a fifth terrestrial planet caused the Late Heavy Bombardment when its meta-stable orbit entered the inner asteroid belt. The hypothetical fifth terrestrial planet, Planet V, had

1856-455: The LHB. Producing the LHB from the collisional disruption of a main belt asteroid was found to require at minimum a 1,000–1,500 km parent body with the most favorable initial conditions. Debris produced by collisions among inner planets, now lost, has also been proposed as a source of the LHB. Evidence has been found for Late Heavy Bombardment-like conditions around the star Eta Corvi . Moon rock Moon rock or lunar rock

1920-441: The LHB. The oldest mineral yet dated on Earth, a 4.404 Ga zircon from Jack Hills, predates this event, but it is likely a fragment of crust left over from before the LHB, contained within a much younger (~3.8 Ga old) rock. The Jack Hills zircon led to an evolution in understanding of the Hadean eon. Older references generally show that Hadean Earth had a molten surface with prominent volcanos . The name "Hadean" itself refers to

1984-478: The Moon have been measured by radiometric dating techniques. They range in age from about 3.16 billion years old for the basaltic samples derived from the lunar maria , up to about 4.44 billion years old for rocks derived from the highlands. Based on the age-dating technique of "crater counting," the youngest basaltic eruptions are believed to have occurred about 1.2 billion years ago, but scientists do not possess samples of these lavas. In contrast,

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2048-433: The Moon on May 8, 2024, and entered lunar orbit for 20 days to find an appropriate landing site. On 1 June 2024, the lander separated from the orbiter and landed on a mare unit at the southern part of the Apollo crater (36.1°S, 208.3°E). The mission objective was to collect about 2 kg of material from the far side of the Moon and bring it back to Earth. The Chang’e-6 probe withstood the high temperatures and collected

2112-530: The alkali suite. Lunar breccias, formed largely by the immense basin-forming impacts, are dominantly composed of highland lithologies because most mare basalts post-date basin formation (and largely fill these impact basins). Mare basalts are named as such because they frequently constitute large portions of the lunar maria . These typically contain 18–21 percent FeO by weight, and 1–13 percent TiO 2 . They are similar to terrestrial basalts, but have many important differences; for example, mare basalts show

2176-474: The asteroid belt reveal numerous ages from 3.4–4.1 Ga and an earlier peak at 4.5 Ga. The 3.4–4.1 Ga ages has been interpreted as representing an increase in impact velocities as computer simulations using hydrocode reveal that the volume of impact melt increases 100–1,000 times as the impact velocity increases from the current asteroid belt average of 5 km/s to 10 km/s. Impact velocities above 10 km/s require very high inclinations or

2240-421: The asteroid belt, increasing the eccentricities of many asteroids until they enter the inner Solar System and impact the terrestrial planets. The Nice model has undergone some modification since its initial publication. The giant planets now begin in a multi-resonant configuration due to an early gas-driven migration through the protoplanetary disk. Interactions with the trans-Neptunian belt allow their escape from

2304-406: The asteroids and the terrestrial planets. While this is required to preserve the low eccentricities of the terrestrial planets and avoid leaving the asteroid belt with too many high-eccentricity asteroids, it also reduces the fraction of asteroids removed from the main asteroid belt, leaving a now-nearly-depleted inner band of asteroids as the primary source of the impactors of the LHB. The ice giant

2368-529: The asteroids heavily concentrated toward the inner asteroid belt, has been shown to be necessary to produce the LHB via this mechanism. An alternate version of this hypothesis in which the lunar impactors are debris resulting from Planet V impacting Mars, forming the Borealis Basin , has been proposed to explain a low number of giant lunar basins relative to craters and a lack of evidence of cometary impactors. A hypothesis proposed by Matija Ćuk posits that

2432-528: The carbon isotopic ratios of some sedimentary rocks found in Greenland were a relic of organic matter: the ratio of carbon-12 to carbon-13 was unusually high, normally a sign of "processing" by life. There was much debate over the precise dating of the rocks, with Schidlowski suggesting they were about 3.8 Ga old, and others suggesting a more "modest" 3.6 Ga. In either case it was a very short time for abiogenesis to have taken place, and if Schidlowski

2496-489: The difficulty of obtaining more, Moon rocks have been frequent targets of theft and vandalism , and many have gone missing or were stolen. Multi-ring basins A multi-ringed basin (also a multi-ring impact basin ) is not a simple bowl-shaped crater , or a peak ring crater , but one containing multiple concentric topographic rings; a multi-ringed basin could be described as a massive impact crater , surrounded by circular chains of mountains resembling rings on

2560-407: The element oxygen . The Apollo Moon rocks were collected using a variety of tools, including hammers , rakes , scoops , tongs , and core tubes . Most were photographed prior to collection to record the condition in which they were found. They were placed inside sample bags and then a Special Environmental Sample Container for return to the Earth to protect them from contamination. In contrast to

2624-419: The establishment of the planetary system, the outermost planets Uranus and Neptune formed very slowly, over a period of several billion years. Harold Levison and his team have also suggested that the relatively low density of material in the outer Solar System during planet formation would have greatly slowed their accretion. The late formation of these planets has therefore been suggested as a different reason for

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2688-500: The form of lunar meteorites are sold and traded among private collectors. Apollo 17 astronauts Eugene Cernan and Harrison Schmitt picked up a rock "composed of many fragments, of many sizes, and many shapes, probably from all parts of the Moon". This rock was later labeled sample 70017. President Nixon ordered that fragments of that rock should be distributed in 1973 to all 50 US states and 135 foreign heads of state. The fragments were presented encased in an acrylic sphere, mounted on

2752-576: The formation of these early rocks in space, and the eventual solidification of Earth's crust, some 700 million years later. This time would include the accretion of the planets from the disk and the slow cooling of Earth into a solid body as the gravitational potential energy of accretion was released. Later calculations showed that the rate of collapse and cooling depends on the size of the rocky body. Scaling this rate to an object of Earth mass suggested very rapid cooling, requiring only 100 million years. The difference between measurement and theory presented

2816-401: The formations of the terrestrial planets, Earth or Venus co-orbitals, and the breakup of a large main belt asteroid. Additional Earth satellites on independent orbits were shown to be quickly captured into resonances during the Moon's early tidally-driven orbital expansion and were lost or destroyed within a few million years. Lunar trojans were found to be destabilized within 100 million years by

2880-403: The formulation of the LHB hypothesis, geologists generally assumed that Earth remained molten until about 3.8 Ga. This date could be found in many of the oldest-known rocks from around the world, and appeared to represent a strong "cutoff point" beyond which older rocks could not be found. These dates remained fairly constant even across various dating methods, including the system considered

2944-658: The future, we will most likely have to make basalt into fibers and use it as building materials," said engineer Zhou Changyi. The samples were placed in the ascent vehicle, which docked with the Chang'e 6 orbiter-return vehicle on June 6, 2024 China's Chang'e 6 lunar probe, carrying the first lunar rocks ever collected from the far side of the Moon, landed in China's Inner Mongolia region on June 25, 2024. More than 370 lunar meteorites have been collected on Earth, representing more than 30 different meteorite finds (no falls ), with

3008-407: The history of late heavy bombardment on the Moon, the youngest large basin discovered, Caloris , is comparable in age to the youngest large lunar basins, Orientale and Imbrium, and all of the plains units are older than 3 billion years. While the cataclysm hypothesis has recently become more popular (in the last fifty years), particularly among dynamicists who have identified possible causes for such

3072-467: The impact the rebound of the surface can obliterate any trace of the initial impact point. Usually, a peak ring crater has a high structure with a terrace and has slump structures inside of it. In 2016, research brought forward new theories about the formation of the lunar mare called Mare Orientale on Earth's Moon . Multi-ring basins are some of the largest, oldest, rarest and least understood of impact craters. There are various theories to explain

3136-438: The inner Solar System, but no consensus yet exists. The Nice model , popular among planetary scientists , postulates that the giant planets underwent orbital migration , scattering objects from the asteroid belt , Kuiper belt , or both, into eccentric orbits and into the path of the terrestrial planets. Other researchers doubt the heavy bombardment, arguing for example that the apparent clustering of lunar impact-melt ages

3200-462: The large eccentricities of asteroids on planet-crossing orbits. Such objects are rare in the current asteroid belt but the population would be significantly increased by the sweeping of resonances due to giant planet migration. Studies of the highland crater size distributions suggest that the same family of projectiles struck Mercury and the Moon during the Late Heavy Bombardment. If the history of decay of late heavy bombardment on Mercury also followed

3264-531: The largest terrestrial meteor impact event to date near the Barberton Greenstone Belt . They estimated the impact occurred about 3.26 billion years ago and that the impactor was approximately 37 to 58 kilometres (23 to 36 miles) wide. The crater from this event, if it still exists, has not yet been found. In the Nice model, the Late Heavy Bombardment is the result of a dynamical instability in

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3328-464: The last few basin-forming impacts were the result of the collisional disruption of a large Mars-crossing asteroid. This Vesta -sized asteroid was a remnant of a population which initially was much larger than the current main asteroid belt. Most of the pre-Imbrium impacts would have been due to these Mars-crossing objects, with the early bombardment extending until 4.1 billion years ago. A period without many basin-forming impacts then followed, during which

3392-471: The last few basins and a change in the size–frequency distribution of craters which formed during this late bombardment as evidence supporting this hypothesis. The timing and the cause of the change in the size–frequency distribution of craters is controversial. A number of other possible sources of the Late Heavy Bombardment have been investigated. Among these are additional Earth satellites orbiting independently or as lunar trojans, planetesimals left over from

3456-689: The latter possibility is the most likely answer. Studies from 2005, 2006 and 2009 have found no evidence for the isotopically-light carbon ratios that were the basis for the original claims of early Hadean life. However, a similar study of Jack Hills rocks from 2008 shows traces of the same sort of potential organic indicators. Thorsten Geisler of the Institute for Mineralogy at the University of Münster studied traces of carbon trapped in small pieces of diamond and graphite within zircons dating to 4.25 Ga. Three-dimensional computer models developed in May 2009 by

3520-473: The lunar magnetic field decayed. Then, roughly 3.9 billion years ago, a catastrophic impact disrupted the Vesta-sized asteroid, significantly increasing the population of Mars-crossing objects. Many of these objects then evolved onto Earth-crossing orbits, producing a spike in the lunar impact rate during which the last few lunar impact basins are formed. Ćuk points to the weak or absent residual magnetism of

3584-575: The lunar surface, and at least some of these should have originated from regions far from the Apollo landing sites. Many of the feldspathic lunar meteorites probably originated from the lunar far side, and impact melts within these have recently been dated. Consistent with the cataclysm hypothesis, none of their ages was found to be older than about 3.9 Ga. Nevertheless, the ages do not "cluster" at this date, but span between 2.5 and 3.9 Ga. Dating of howardite , eucrite and diogenite ( HED ) meteorites and H chondrite meteorites originating from

3648-419: The most accurate and least affected by environment, uranium–lead dating of zircons . As no older rocks could be found, it was generally assumed that Earth had remained molten until this date, which defined the boundary between the earlier Hadean and later Archean eons. Nonetheless, in 1999, the oldest known rock on Earth was dated to be 4.031 ± 0.003 billion years old, and is part of the Acasta Gneiss of

3712-464: The outer Solar System. The original Nice model simulations by Gomes et al. began with the Solar System 's giant planets in a tight orbital configuration surrounded by a rich trans-Neptunian belt . Objects from this belt stray into planet-crossing orbits, causing the orbits of the planets to migrate over several hundred million years. Jupiter and Saturn's orbits drift apart slowly until they cross

3776-404: The resonances after several hundred million years. The encounters between planets that follow include one between an ice giant and Saturn that propels the ice giant onto a Jupiter-crossing orbit followed by an encounter with Jupiter that drives the ice giant outward. This jumping-Jupiter scenario quickly increases the separation of Jupiter and Saturn, limiting the effects of resonance sweeping on

3840-572: The same three Luna 16 rock fragments sold for US$ 855,000 at Sotheby's. In 2020, Chang'e 5 , the fifth lunar exploration mission of the Chinese Lunar Exploration Program , returned approximately 1,731 g (61.1 oz) of rocks and dust from the Oceanus Procellarum, (the Ocean of Storms), the largest dark region on the Moon, visible on the western edge. The Chang'e-5 samples contain 'perplexing combination' of minerals and include

3904-504: The samples by drilling into the Moon's surface and scooping soil and rocks with a mechanical arm, according to a statement from the China National Space Administration (CNSA). The collected rock was crushed, melted and drawn into filaments about one third of the diameter of a human hair, then spun into thread and woven into cloth. "The lunar surface is rich in basalt and since we're building a lunar base in

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3968-427: The significance of the lack of impact melt rocks older than about 4.1 Ga. One hypothesis for this observation that does not involve a cataclysm is that old melt rocks did exist, but that their radiometric ages have all been reset by the continuous effects of impact cratering over the past 4 billion years. Furthermore, it is possible that these putative samples could all have been pulverized to such small sizes that it

4032-455: The sixth new lunar mineral, named Changesite-(Y). This phosphate mineral characterized by colorless, transparent columnar crystals. Researchers estimated the peak pressure (11-40 GPa) and impact duration (0.1-1.0 second) of the collision that shaped the sample. Using shock wave models, they estimated the resulting crater to be between 3 and 32 kilometers wide, depending on the impact angle. The follow-up mission to Chang'e 5, Chang'e 6 , reached

4096-507: Was correct, arguably too short a time. The Late Heavy Bombardment and the "re-melting" of the crust that it suggests provides a timeline under which this would be possible: life either formed immediately after the Late Heavy Bombardment, or more likely survived it, having arisen earlier during the Hadean . A 2002 study suggest that the rocks Schidlowski found are indeed from the older end of the possible age range at about 3.85 Ga, suggesting

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