This showed that the planets were in what chemists call the 'equilibrium state', whereby an atmosphere made of carbon dioxide indicates a lifeless state. When we looked at the atmosphere of the Earth, it was such a rich mixture, almost like the gas that goes into the intake manifold of your car - hydrocarbons mixed with oxygen. Mars' atmosphere, in comparison, is more like the exhaust gases that come out the other end. So it appears that life on Mars and Venus may have exhausted itself. The image of the planet from space seems to have had a profound impact on global consciousness.
Some people cite it as the birth of the environmental movement.
Yes, I think it did. Though I think the environmental movement was born with the publication of Rachel Carson's Silent Spring in 1962 - with the negative discovery that there were pesticides everywhere, from Antarctica to the North Pole. Interestingly, she would not have been able to write that book without the electron capture detector, which I had invented a few years previously and which enabled us to measure levels of pesticide traces around the world. There is an a obvious analogy between Gaia as a scientific theory and the animistic beliefs of indigenous cultures and their reverence for the Earth as The Mother, or even Plato's belief that the planet was one living organism. Well, there is a sort of thread of revolutionary thinking going right through science back to the Enlightenment in the 18th century.