Geology Reference
In-Depth Information
mosphere. After all, he reasoned, life radically alters the Earth's atmosphere by using it
as a source of raw materials and as a repository for exhaled gases such as oxygen and
methane, keeping our atmosphere far from chemical equilibrium and making it highly
reactive. Perhaps the same would be true of Mars if it bore life. NASA greeted this sug-
gestion with enthusiasm, and so Lovelock began work on an instrument for analysing
the Martian atmosphere to be put on board the Viking mission to the red planet. Then
misfortune struck. The US government cancelled the mission, and Lovelock's work was
stopped.
But this was not the end of Lovelock's idea. The intensity of his work on life de-
tection had prepared the ground for the startling intuition that was to vastly expand our
understanding of our planet. One afternoon in September of 1965, the astronomer Lou
Kaplan brought a freshly minted data set from the Pic de Midi telescope in France to
Lovelock's office, where he was working with the philosopher Diane Hitchcock. The
Pic de Midi data, which had been collected using an Earth-based telescope, revealed the
atmospheric compositions of both Mars and Venus. Lovelock knew nothing about Gaia
as he began to ponder these data. He had never thought about the Earth as a living or-
ganism, but he was about to receive an insight that has revolutionised our scientific un-
derstanding of our planet and of our place within it, an insight strangely in tune with the
animistic perceptions of traditional peoples around the world and of the pre-scientific
West.
Being a skilled chemist, Lovelock soon realised that the Pic de Midi data held a
powerful message, for the atmospheres of Mars and Venus were at chemical equilibri-
um, consisting mostly of carbon dioxide. No chemical reactions were going on at all,
rather like a party where everyone is utterly exhausted and has gone to sleep, when no
one has any energy left for conversation, for the exchange of addresses and phone num-
bers, for dancing, and for invitations to further parties. The Earth's atmosphere is rad-
ically different, being full of gases that react quickly and sometimes violently together
in the presence of sunlight such as oxygen and methane, giving water and carbon diox-
ide. The Earth's atmosphere is therefore far from equilibrium, and displays an amazing
amount of chemical activity amongst its reactive gases, much like a party in full swing
where people have plenty of energy for dancing and for lively conversations.
The contrast between the atmospheres of Earth and Mars amazed Lovelock, and he
knew the difference must be due to the presence of life on the Earth's surface. Life pro-
duces oxygen by means of photosynthesis, in which organisms like plants and phyto-
plankton (perhaps more aptly dubbed “photoplankton”) use the sun's energy to split wa-
ter, giving hydrogen that they combine with carbon dioxide inhaled from the atmosphere
to make energy-rich sugars. In the process, oxygen is set free in the air, where it reacts
with methane produced by bacteria in the mud at the bottom of lakes, in marine sedi-
