Researchers from biologists to astrophysicists use complex computer models to predict the eventual extinction of the human race. Many of these models indicate that our species may survive for another century or two—a thousand years, possibly. Beyond that, however, the outlook seems grim. Name your poison:

Climate change dries up much of the planet, ruins our food crops, makes the oceans rise, and triggers a refugee crisis and global wars.

Nuclear war or terrorism causes a breakdown of civilization and mass starvation.

An epidemic decimates the population too fast for a cure.

An asteroid or comet smashes into the planet, causing a cataclysm of volcanic eruptions, earthquakes, tsunamis, and a pall of ash that destroys almost all crops.

Cosmic rays from a quasar silently kill all living things on Earth.

Most of us may have forgotten a real-live doomsday scenario that I left off the list: the hole in the ozone layer. During the 1970s, scientists speculated that chloro uorocarbons, or CFCs, posed a risk to Earth’s atmospheric sunscreen, a layer of oxygen molecules that shield the planet from deadly ultravioletrays. Research con rmed that a hole in the layer had opened up over Antarctica. NASA sent up satellites during the mid-Eight- ies to measure the extent of the problem. From the vantage point of space, they proved that the hole not only existed, it was expanding rapidly. Eventually, the ozone would disappear altogether. The research was so conclusive that, in 1987, every member of the United Nations signed a protocol to phase out the use of CFCs in aerosol sprays and refrigeration. Scientists now predict that the ozone layer will fully recover by 2070. In short, we are not going to die from hairspray.

But what about the problems that remain? NASA satellites look back at Earth more completely than any other nation’s satellites, public or private. We happen to be very good at taking sel es of our own planet. These satellites show the amazingly complex relationships among the atmosphere, the oceans and land ecosystems—all the systems we have to know to correct those factors that tend to make our planet inhabitable to humans.