And It’s All We Have… For Now

Sooner or later, everybody who is interested in space and astronomy gets a look at our planet from “the outside.”  This image, from the Galileo spacecraft during one of its swings around Earth, tells a pretty remarkable story. If you were an incoming alien vessel, you’d see evidence of water. The oceans tell that story, but so do the clouds because they’re made of water vapor. The land masses would tell you that there are places to land on this planet, but at this distance and resolution, you wouldn’t be able to make out plants and animals… or humans and their cities.

If your alien ship had special sensors, it could use spectral analysis to dissect the gases in the atmosphere that blankets the planet. You would find oxygen, nitrogen, plus trace amounts of other gases.  Oh, and carbon dioxide. That’s a biggie. Carbon dioxide (you sometimes see it as CO₂) is a by-product of living and geological processed. And, it’s the principal component of the greenhouse gases that we are pumping into our atmosphere from energy generation (driving cars, making electricity, powering manufacturing, etc.). The more greenhouse gases we load into the atmosphere, the warmer our climate is getting. And this is having an effect that future spacecraft will see (and we will have to live with).

As you can see from this picture, our atmosphere looks pretty thin when compared to the vastness of space and the size of our own planet. In fact, if you look at other planetary atmospheres in the solar system, you find them to be thick and heavy (Venus, the gas giants), or thin and possibly even fragile (Mars, Earth, some of the smaller moons of the outer solar system). What we learn about atmospheres is important, since our own planet has the only one that we know of that has harbored (and possibly even helped begin) life.  That makes what we’re doing to it with carbon dioxide a pretty major “experiment.”