This summer, an alien world will approach Earth closer than it has since Neanderthals roamed our planet, over 60,000 years ago. This celestial body, half the size of Earth, has a surface area equivalent to all the dry land of our world. It is a place where the air pressure is as thin as it is 20 miles above Earth’s surface and the average ground temperature makes Antarctica seem comparatively balmy. Deadly ultraviolet radiation from the Sun constantly bathes the planet unchecked by any natural protection as on Earth.
