In 1990, Voyager 1 captured the most distant portrait of our planet ever taken, revealing that from beyond Pluto's orbit, Earth appears as nothing more than a "pale blue dot." In a new study, researchers have tested whether Earth's color is a unique feature of life-friendly planets. If so, searching for exoplanets displaying this hue could help in singling out worlds potentially brimming with alien life.
As it turns out, Earth's delicate color can be closely mimicked by hypothetical exoplanet types that are completely uninhabitable. A broader portion of Earth's overall spectrum, however, does display a subtle signature only attributable, insofar as we know, to life. Seeking this signature from pale blue worlds in stars' habitable zones with future telescopes could be a powerful tool for identifying worlds deserving of intense further scrutiny.
"One important takeaway is that color should be used with caution because we found it's relatively easy to make lifeless planets that are pale blue in color," said lead author Joshua Krissansen-Totton, a doctoral student at the University of Washington. "With that said, I was very excited to find that Earth's spectrum has an intriguing signature that is biogenic, unique and potentially quite useful." [10 Exoplanets That Could Host Alien Life]