Earth scores surprisingly low on an index of potential habitability

The Earth is capable of supporting life. We know this because we’re standing on it and breathing at the same time. But what if we were extraterrestrials living on another planet somewhere far off in the universe? Would we be able to tell that this world could support living organisms?

Possibly, according to astronomer Rory Barnes of the University of Washington-based Virtual Planetary Laboratory, who in a new study used a variety of measurements and calculations as a way to gauge the relative habitability of our home world. His research found that Earth a rating of just 82 percent, making it a good candidate for biological life, but not a great one.

Barnes, a research assistant professor of astronomy, and his colleagues developed a “habitability index for transiting planets” which they use to rank exoplanets to help identify priority candidate worlds in the search for alien life. Among the factors analyzed in the ranking system is the radius and distance of a planet’s orbital path, the size of the planet, the amount of energy it gets from its host star, and the mass and radius of that star (which is estimated using spectrometry).

Using this data, they create a model of a planet and compare its “measurements” to those known from other worlds in an attempt to sort out the likelihood that an exoplanet would be capable of supporting biological life. In their new study, they turned the microscope on our own homeworld and examined it as if it were a far-off planet – with rather surprising results.

Believe it or not, our planet is actually too close to the sun

It seems impossible that a planet known to support complex biological organisms would end up scoring anything less than a perfect 100 percent on a habitability index, but as the study authors pointed out, Earth – objectively speaking – is not exactly an ideal planet for life.

“Basically, where we lose some of the probability, or chance for life, is that we could be too close to the star,” Barnes explained in a statement. “We actually are kind of close to the inner edge of the habitable zone. If we spotted Earth with our current techniques, we would reasonably conclude that it could be too hot for life.”

In addition to being too close to the edge of the habitable zone, the area surrounding a star where an orbiting rocky planet could maintain surface water, Earth’s composition and orbital path, plus the behavior of other nearby worlds, make the planet a less-than-perfect candidate in terms of the habitability index, according to the researchers behind this new report.

“Remember, we have to think about the Earth as if we don’t know anything about it. We don’t know that it’s got oceans, and whales and thing like that – imagine it’s just this thing that dims some of the light around a nearby star when it passes,” said Barnes.

Even if we discovered a new planet that was Earth’s twin and orbited around a star that was just like the sun, he and his colleagues said, we might not choose to explore it too closely if we found another world that ranked higher on the index of habitability at the same time. That other world, they explained, would actually be the safer bet when it comes to supporting biological life.

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Feature Image: NASA