“…This modeling should help identify the regions of parameter space that each mass‐loss mechanism dominates. Further, observations of atmospheric escape for the emerging class of very young planets that are the likely antecedents of mature sub‐Neptune size planets (David, Cody, et al., 2019; David, Petigura, et al., 2019; David et al., 2016; Newton et al., 2019; Plavchan et al., 2020; Rizzuto et al., 2020) offer the hope of distinguishing between the photoevaporative and core‐powered atmospheric loss mechanisms. Ultimately, our quantitative insights into how these planets formed, such as the core‐mass function and how much H/He these planets accreted, depend strongly on the assumed mass‐loss model.…”