Solar System in fiction close to the Sun and its surface was exposed to extremes of temperature. The asteroids were too tiny and airless. By the early 20th century, prospects for life in the Solar System focused on Venus, the larger moons of Jupiter and Saturn, and especially Mars. With the onset of the Space Age, planetary probes cast increasing doubt on the likelihood of extraterrestrial life in the Solar System, at least life of any magnitude greater than organisms such as bacteria. By the mid-1960s, it was firmly established that life could have no foothold on the hostile surfaces of Mercury or Venus,
Wonders of the Solar System by John Herschel's actinometer. He also travels to Norway to observe and explain the defensive role of the Earth's magnetosphere against the sun's solar wind and its role in forming the Aurora Borealis. He also relates the Voyager missions and their continuing exploration of the massive reach of the sun's gravitational forces on objects in the farthest regions of the solar system. Finally, in the clear skies of the Atacama Desert, at the Paranal Observatory he is able to observe, with the naked eye, the myriad of stars on the Milky Way and relates the meaning of their diverse colours