Really really really old oceans

by David Sugarman

Ever wonder how long the Earth has had oceans? And how long has the solid rocky stuff that forms the Earth's crust been around? How would you even go about finding out?

A team of scientists from Australia, the United States and Scotland went about answering these questions by examining microscopic zircon crystals in sediment from Jack Hills, Western Australia. Zircons are the oldest minerals found in the Earth's crust. Anything older was destroyed by the meteors that bombarded our planet after its formation about 4.55 billion years ago.

Zircon contains radioactive uranium that is slowly decaying to lead. By knowing how long it takes for uranium to change to lead, and by measuring the amount of lead and uranium in the zircon, scientists can estimate the age of the mineral sample.

In addition, by measuring the amount of a certain type of oxygen trapped in the zircon, these scientists were also able to estimate the age of the oceans that must have cooled the newly formed zircon in the rocky crust below.

They were surprised to find that the zircon was 4.4 billion years old, indicating that the oceans and the continental crust they sit on are about 130 million years older than previously thought.

Since there seem to have been oceans way back then, perhaps life evolved earlier than the current estimate of 3.8 - 3.5 billion years ago.

Think about it. The water we enjoy is crucial to life and distinguishes us from all the other planets by its abundance. It has been around almost from the beginning. Maybe we should rename our planet "Water".