THE CLOSEST POTENTIALLY HABITABLE PLANET HAS AN INTRIGUING INTERIOR
If Proxima b is a cannonball-like world like Mercury, it would be about 6 percent smaller than Earth. This dense, completely dry version of the planet would consist of a metal core making up about two-thirds of the planet’s mass sheathed by a rocky shell.
On the other hand, if Proxima b is made up half of water ice like Saturn’s largest moon Titan might be, it would be roughly 40 percent bigger than Earth. In this scenario, the planet would be covered completely in water about 120 miles deep. Under this global ocean, the pressure would be so strong that water would turn into a layer of high-pressure ice, which would sit on top of a rocky mantle and a metal core.
These findings suppose that the abundances of elements in Alpha Centauri are similar to those in the solar system, and there is no guarantee that is the case, says planetary astronomer Franck Marchis, chair of the exoplanet group at the SETI Institute in Mountain View, California, who did not take part in this research. Brugger agrees, noting that future observations of Proxima Centauri’s elemental abundances could improve their models and help pin down which version of Proxima b is more likely.
And who knows, “with the Breakthrough Starshot project, maybe in 20 to 40 years, we’ll have pictures of Proxima b, telling us exactly what it looks like,” Brugger says.
The scientists detailed their findings Oct. 17 at the meeting of the American Astronomical Society Division for Planetary Sciences and the European Planetary Science Congress in Pasadena, California.