IT鈥橲 known as the Hadean eon, from the Greek word for hell. But the early Earth probably looked much as it does today.
A study of zircons, the oldest minerals on Earth, suggests that massive amounts of continental crust were formed soon after Earth鈥檚 creation 4.56 billion years ago.
Mark Harrison at the Australian National University in Canberra and his team looked at the ratio of hafnium isotopes, which change as a result of the radioactive decay of lutetium, to lutetium itself in 100 zircons dating back between 4 billion and 4.37 billion years. The minerals came from the Jack Hills in Western Australia.
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Lutetium is retained in the melting Earth鈥檚 mantle, whereas hafnium becomes part of the continental crust. High hafnium ratios in the ancient zircon samples indicate that, at the time they were formed, much of the mantle had melted and cooled to produce crust (Science, DOI: 10.1126/science.1117926). 鈥淭here have to have been continents, and lots of them,鈥� says Harrison.
Earlier work suggests that the young Earth was also abundant in water, painting a very different picture of the Hadean from the traditional concept of a barren, arid world where rocks formed largely from impacts with extraterrestrial objects.
鈥淚t may have looked similar to the present day,鈥� says Harrison. 鈥淚f you could go back in a time capsule 4.4 billion years, you鈥檇 see a similar amount of continent, blue oceans, sandy beaches and blue skies.鈥�
