Lecture 2 - The outer solar system and life

From ancient organisms to the plants and animals we see today, our planet showcases a spectacular array of life. But beneath such diversity lies an underlying unity. All life on Earth is based on two molecules (the proteins and the nucleic acids) and the origin of these molecules in the early stages of our planet’s development is inextricably linked to the origin of life.

In his second Christmas Lecture, Carl Sagan travels beyond Earth to explore the possibility of life in outer space.

To find the answer, he looks back to the early stages of the development of our atmosphere. The hydrogen from this atmosphere has since escaped to space from Earth, but not from bigger planets like Jupiter. When the hydrogen-rich gases of the early Earth are mixed together and supplied with energy, the essential molecular building blocks of the proteins and nucleic acids are formed.

As Sagan suggests, although this process no longer occurs on Earth, such organic chemistry should be occurring in the outer solar system on Jupiter, and Titan, Saturn’s largest moon. The NASA twin spacecraft Voyager 1 and 2, launched a few months prior to these Lectures in 1977, were sent to space to explore this hypothesis. 




Carl Sagan



All lectures in the series