Moons of Mars satellites, Earth had one and Jupiter had four (known at the time), that Mars by analogy must have two. Furthermore, as they had not yet been discovered, it was reasoned that they must be small and close to Mars. This would lead Swift to making a roughly accurate estimate of their orbital distances and revolution periods. In addition Swift could have been helped in his calculations by his friend, the mathematician John Arbuthnot. Voltaire's 1752 short story "Micromégas", about an alien visitor to Earth, also refers to two moons of Mars. Voltaire was presumably influenced by Swift. In recognition of
The Living Cosmos about the setting of the Earth and the events that have occurred on this planet. Subsequent chapters consider the origin of life on Earth, and the physical extremes to which life as adapted. In astrobiology, it pays to think “outside the box” and imagine how strange life might be or whether post-biological evolution is possible, where the basis is mechanical or computational. A chapter on evolution shows how it is affected by the cosmic environment. Possibilities of life in the Solar System are considered next, with emphasis on Mars, Titan, and outer moons harboring liquid water. Next is a summary