NASA’s Proposed EVE Mission Aims to Solve the Radius Valley Mystery

A debate has been raging amongst planetary scientists for over a decade - why are there so few exoplanets with a radius of about 1.8 times that of the Earth? Exoplanets are currently largely grouped into two distinct groups - “super Earth” are below that size and have rocky interiors, whereas “Sub-Neptunes” are above that size limit and appear “puffier.” But we don’t really understand what about the path of planetary evolution forces this bifurcation. A new mission proposal, called the Early eVolution Explorer (EVE) wants to find out, and a draft of its concept can be found in pre-print form on arXiv.