Winston Churchill's views about life on other planets revealed in essay
The existence of alien life on other planets may not have been the most pressing issue facing Winston Churchill in 1939, with Europe on the brink of war.
But it was something he thought about deeply, a newly unearthed essay written by the wartime leader has revealed.
In the 11-page article, entitled "Are We Alone in the Universe?" Churchill muses about the possibility of life evolving elsewhere in the Solar System and beyond.
Pre-empting discoveries of extra-solar planets by more than five decades, he defines what scientists later called the "habitable" or "Goldilocks" zone - the narrow orbital region where a planet is not too hot or too cold but "just right" to support life.
Correctly, he believed large numbers of stars could have families of planets.
Also correctly, he concluded that many of them " will be the right size to keep on their surface water and possibly an atmosphere of some sort" and some would be "at the proper distance from their parent sun to maintain a suitable temperature".
The essay - possibly intended for publication in the Sunday newspaper The News of the World - had been hidden away at the US National Churchill Museum in Fulton, Missouri, since the 1980s.
The document was rediscovered last year by the museum's new director Timothy Riley, who passed it on to Israeli astrophysicist, author and former Hubble Space Telescope scientist Mario Livio.
Describing the find in the journal Nature, Professor Livio said it came as a "great surprise," despite Churchill's well-known interest in science.
Churchill was the first prime minister to hire a science adviser, and in the 1920s and 30s wrote a number of popular science essays for newspapers and magazines on topics such as evolution and cells.
In one 1931 article for The Strand Magazine, entitled "Fifty Years Hence" he predicted the invention of hydrogen-fuelled nuclear fusion power.
Churchill regularly met scientists such as Bernard Lovell, the father of radio astronomy.
His article about alien life was written soon after the 1938 radio broadcast by Orson Welles dramatising The War Of The Worlds by HG Wells, which caused widespread panic among listeners in the US who thought they really were being invaded by Martians.
At the time there was much speculation about the possibility of life on Mars.
Churchill concluded that due to their distance from the sun, Mars and Venus were the only two places in the Solar System other than Earth that could conceivably harbour life.
With a nod to the grim events unfolding in Europe, he wrote: "I for one, am not so immensely impressed by the success we are making of our civilisation here that I am prepared to think we are the only spot in this immense universe which contains living, thinking creatures, or that we are the highest type of mental and physical development which has ever appeared in the vast compass of space and time."