A Near-Earth-size Planet Isn’t Necessarily JUST Like Earth

The news last week that the Kepler telescope had found a close “cousin” of Earth circling a sun-like star really brought out the speculation among people who don’t actually study planets for a living. The press, of course, ran with the story, calling it “Earth 2.0” and “Earth-like”, neither of which is quite true. However, despite the tendency of supermarket rags as well as serious press to jump on stories like this and carry them to illogical extremes, the discovery of this planet IS a milestone in exoplanet research.

Kepler-452b IS likely to be a rocky world similar to Earth, although astronomers haven’t confirmed that yet. It’s in the habitable zone of its star, so that means liquid water could exist on its surface. Whether it has water, or even an atmosphere, is all still to be determined. This planet is near-Earth-size, meaning it’s close to our planet’s size. Actually, it’s 60 percent larger than Earth, and its 385-day year is slightly longer than our 365-day year. It’s about a billion and a half years older than Earth, which has interesting implications for the evolution of life. Life began on Earth some 3.8 billion years ago, and this new planet has had a LOT longer than that to cook up some life.

Still, that’s not enough to make it Earth 2.0.

Yet.

For that to happen, we’ll need to know more about its atmosphere — including finding any telltale tracers for life. The planet’s star is very much like our Sun, and in the grand scheme of things, since life evolved to take advantage of what the Sun has to offer, it will be interesting to find out, someday in the distant future, what sort of life Kepler-452b has got on its surface.

All of us who read science fiction know about the countless worlds that populate the stories we read. Many times they ARE Earth-like, but supporting entirely different forms of life than what we have here. That makes sense — the universe is the ultimate generator of infinite diversity in infinite combinations. The boundary conditions — that is, the starting collection of compounds from which life can arise — may well be slightly different from what we know here on Earth. Or, it could be a LOT different. And those differences all but guarantee that life elsewhere isn’t going to look like us.

But, it’s fun to think about life elsewhere as we gaze at a starlit sky, or browse through the artist’s concepts of worlds that Kepler and its partner observatories have found. That’s the sort of stuff that keeps us going, striving to explore ever further out in the galaxy. It’s what we do.