A proposed NASA mission called the Early eVolution Explorer (EVE) aims to solve a decade-old puzzle in planetary science: why so few exoplanets have a radius of about 1.8 times that of Earth. A concept draft of the mission has been published on arXiv.
The so-called radius valley separates exoplanets into two distinct groups: super-Earths, which are smaller with rocky interiors, and sub-Neptunes, which are larger and puffier. Researchers have struggled to explain what forces drive this evolutionary split.
The EVE mission would study nearby exoplanets to uncover the physical mechanisms behind this bifurcation. It seeks to understand why planetary evolution consistently produces these two distinct size classes rather than a continuum.
If selected, EVE would mark a focused effort to directly address one of the most persistent questions in exoplanet science. Understanding the radius valley could reshape theories of planetary formation and evolution across the galaxy.
A preprint of the concept is currently available for peer review. No timeline for potential selection has been announced.