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#1 The Earth is old, and it is a curious fact that the lifespan of the Earth is easier to understand than our own. The properties of the star that warms it are easily determined by the astronomers. Our star is a main sequence star, and it has been warming up for the past few million years, threatening life on Earth.

#2 The Earth is getting older and more fragile, and it is only Earth that has incubated a creature capable of knowing the cosmos. But the existence of that creature is imperilled. We are unique, privileged beings, and we should cherish every moment of our awareness.

#3 The threat of human extinction is always imminent. We are very fragile understanders, and we precariously cling to Earth, our only home. Asteroid strikes could destroy the biosphere on which we depend, just as one seems to have ended the reign of dinosaurs 65 million years ago.

#4 The idea that Mars could be a refuge for humanity if our life on Earth was in danger of being terminated is extremely strange. The assumption is that the surface of Mars is not so different from that of the Saharan or Australian deserts, and that all we would need to do is drill down to an aquifer.