TIME OF FORMATION OF THE EARTH'S CORE.

摘要: ACCORDING to several theories1–3, the Earth was formed by accretion from a mixture of silicate particles and metal particles, something like those in chondritic meteorites. The accreting material may also have contained relatively small quantities other components such as iron meteorites4 carbonaceous chondrites5. Most advocates these theories maintained that occurred slowly (over period about 108 yr), so gravitational potential energy efficiently radiated away cool unmelted condition. Subsequently, heating long lived radioactive elements occurred, leading melting phase segregation core. Differentiation formation core thus much later than primary Earth. It has even been argued might not yet proceeded completion1,6,7. On hand, alternative origin Earth8–10,11 high temperature conditions either during or very soon afterward. Clearly, an independent determination time interval ΔTc between would crucial bearing on contrasting theories.