Neptune-like worlds could become habitable

Planet transformation can bring water to otherwise dry region

Habitable planet illustration

MINI-NEPTUNES  Habitable planets around cool stars (illustrated) could start off as Neptune-like worlds farther from their suns.

NASA Ames, SETI Institute, JPL-Caltech

To create an Earthlike planet, try starting with a world more like Neptune.

A small gas planet that drifts inward from the cold outer reaches of a solar system might transform into a rocky world loaded with water and other riches, researchers report in the January Astrobiology. This process could create habitable worlds in places that might otherwise be dry and sterile.

Rodrigo Luger, an astronomer at the University of Washington in Seattle, and colleagues used computer simulations to learn the fate of mini-Neptunes dragged inward by the gaseous disk encircling a young red dwarf star. The astronomers found that the planet could end up in the habitable zone, the region around the star suitable for liquid water. Ultraviolet radiation from the star could bake off the planet’s thick atmosphere, leaving behind an ice-rich rocky core.

Rocky planets that form in the habitable zone, on the other hand, start off dry. These worlds are too small to attract water vapor and they form in a region that’s too warm for ice. By starting the planet far from the star, where ice is plentiful, and moving it closer, the world stands a better chance of supporting an environment where life could flourish.

Christopher Crockett is an Associate News Editor. He was formerly the astronomy writer from 2014 to 2017, and he has a Ph.D. in astronomy from the University of California, Los Angeles.

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