The first indisputable evidence for very early differentiation of the silicate Earth came from the extinct 146Sm-142Nd chronometer. 142Nd excesses measured in 3.7-billion-year (Gyr)-old rocks from Isua (southwest Greenland) relative to modern terrestrial samples imply their derivation from a depleted mantle formed in the Hadean eon (about 4,570-4,000[thinsp]Gyr ago). As dictated by mass balance, the differentiation event responsible for the formation of the Isua early-depleted reservoir must also have formed a complementary enriched component. However, considerable efforts to find early-enriched mantle components in Isua have so far been unsuccessful. Here we show that the signature of the Hadean enriched reservoir, complementary to the depleted reservoir in Isua, is recorded in 3.4-Gyr-old mafic dykes intruding into the Early Archaean rocks. Five out of seven dykes carry 142Nd deficits compared to the terrestrial Nd standard, with three samples yielding resolvable deficits down to -10.6 parts per million. The enriched component that we report here could have been a mantle reservoir that differentiated owing to the crystallization of a magma ocean, or could represent a mafic proto-crust that separated from the mantle more than 4.47[thinsp]Gyr ago. Our results testify to the existence of an enriched component in the Hadean, and may suggest that the southwest Greenland mantle preserved early-formed heterogeneities until at least 3.4[thinsp]Gyr ago.
Cuando Fernando de Magallanes zarpaba del puerto de Sevilla, el 10 de agosto de 1.519, no sólo iniciaba la que habría de ser primera vuelta a nuestro planeta, demostrando así de forma práctica y fehaciente la esfericidad de la Tierra, sino que también partía hacia cielos desconocidos para los 234 marineros que componían la tripulación […]
En un mundo lejano, el color el Sol se oscurecerá gradualmente. Se volverá naranja y, después, rojo. Crecerá hasta que sus capas exteriores lleguen hasta la misma órbita de la Tierra. Las estrellas no son eternas: nacen y mueren. Actualmente, nuestro Sol tiene unos 5000 millones de años y deberán pasar otros 5000 millones antes …
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