Habitable Conditions on the Early Earth

Direct information concerning the first 500 million years of Earth history – the Hadean Eon – is very limited, since practically no crustal rocks from that time have survived. We do know that the Earth collided much more frequently than it does today with asteroids and comets, as witnessed by the heavily cratered highlands of the Moon. Astronomers also tell us that the Sun was about 30 percent fainter then, so that the Earth may have been cold, unless there was a large greenhouse effect to trap the Sun’s heat and raise surface temperatures above the freezing point. Also of special interest is the apparent fact that life arose on Earth either during or shortly after the Hadean Eon.

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January 23, 2006 / Posted by: Shige Abe

A Mild, Habitable Hadean?

NAI’s Mark Harrison of the UCLA team co-authored a study published in this week’s Science describing a titanium thermometer technique used to measure the temperature at which ancient zircons from the Jack Hills in Western Australia formed. The results paint a mild picture of the Hadean, complete with an atmosphere and liquid water.

May 9, 2005 / Posted by: Shige Abe