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Space Topics: Earth

Earth is a Planet, Too

by Charlene M. Anderson

The Space Age has brought much good and much evil to the Earth-born species that created it. With magnificent technology and Promethean effort, humans walked upon the Moon. With intricate and imaginative communication satellites, we "shrank" our planet. We invented new electronic senses to watch Earth -- and each other -- from orbit. We built weapons that could destroy the world as we know it, and from them, created rockets to take us to space.

Perhaps most important, in this Space Age, we took a few remarkable photographs that changed forever the way we see our planet. The Apollo astronauts on the way to the Moon turned their cameras back on Earth and photographed a warm and nurturing, but small and ineffably lonely, planet drifting through space.

Click to enlarge > Iconic view of Earth from Apollo 17 One of the most famous images of the twentieth century, this view of the fully lit globe of Earth was taken from Apollo 17 shortly after its launch on December 7, 1972. Credit: NASA

It's no coincidence that, after seeing these photographs, many people were so impressed by the fragility of Earth that they joined the emerging environmental movement. Indeed, those Space-Age images may have provided the impetus the fledgling movement needed to get off the ground.

1970 -- Earth Day

On April 22, 1970, environmentalists proclaimed the first Earth Day, to "raise the consciousness" of people about the dangers that were beginning to reach global proportions. With their own eyes, people could now see that Earth was a small planet. Local activities, such as dumping toxic wastes into rivers, could spell disaster for someone downstream and, eventually, on the other side of the world.

The maturing space program advanced our knowledge of how Earth works. We saw better how seemingly benign or unconnected actions can cause harm planet-wide. Using the runaway greenhouse of Venus as an example, scientists modeled atmospheric processes on Earth, and grew alarmed about the warming of greenhouse gasses here. The destructive effects of chlorofluorocarbons on Earth's protective ozone layer were predicted by scientists using models of aerosol chemistry in Venus' atmosphere. Scientists who studied planet-wide dust storms on Mars realized that they could be analogs for atmospheric effects on Earth after a nuclear war, which eventually led to the concept of "nuclear winter."

The planetary program has contributed much more than inspirational images to environmental awareness.

2050 -- Mars Day?

On the eightieth anniversary of Earth Day, humans may look back on their home from the surface of another planet. By 2050, we could be exploring Mars to answer questions that bear on our own planet. Did this most Earth-like of planets once harbor life? If it did, what happened to the Martian lifeforms? Could we -- and should we -- introduce terrestrial life to an alien world?

With our technology and effort, we will someday reach out to another planet. When humans explore Mars, we will find out if this new world can support our striving and contentious species. If we have learned the lessons taught on all the Earth Days from 1970 to 2050, it may be that wiser and more careful beings step onto Mars than stepped onto the Moon.

The Planetary Society is working toward that day.