Despite the surface beauty of planets and stars, what lies beneath is increasingly seizing astronomers’ attention. The interiors of celestial bodies, scientists now realize, may be crucial to understanding the prospects for life elsewhere in the universe.
Part of the new thinking comes from a better appreciation of how living things depend on what’s inside our own planet. Present theory holds that there is a Pluto-size solid iron ball at Earth’s center surrounded by an extensive zone of liquid iron. The circulation of this molten metal may produce the geomagnetic field that shields us from potentially lethal solar flares and cosmic rays. Above the two-part core lies the mantle, a 1,800-mile-thick expanse of hot, pliable rock. The slow churning of the mantle pulls in carbon compounds from the ocean floor and spits out carbon dioxide in volcanic eruptions, regulating global climate. The mantle’s movements also rearrange Earth’s geography, giving rise ...
