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
A Beautiful Planet does not have a planetary magnetic field. Consequently, "its atmosphere was ripped away from the planet by the solar wind. If you could stand on Mars today, you would find a landscape of lifeless desolation; very cold, and very dry." One of the current challenges in maintaining Earth's planetary "life support system" is global warming. The film shows how Earth's warming climate is causing the Greenland ice sheet to melt, and drives the point home by showing the Jakobshavn Glacier calving an incredibly large number of icebergs in relatively rapid succession as the end of this flowing river of ice