The vast majority of detected exoplanets orbit their star in less than a month, in extreme conditions unmet in the Solar System. A striking feature in the demography of these close-in planets is the deficit of Neptune-size planets on very short orbits, also known as the <b>'hot Neptune desert'</b>, which challenges our understanding of planet formation and evolution.<div><br></div><div>Two categories of mechanisms are thought to play a predominant role in the formation of the desert: <b>orbital migration</b>, which brings these planets close to their star, and <b>atmospheric escape</b> due to the resulting increased irradiation. Yet, their relative roles remain poorly assessed, partly because we lack numerical models that investigate the interaction between the structure of the planet, the evaporation of its atmosphere, and the evolution of its orbit over the long term. </div><div><br></div><div>To address this need, we have developed an advanced model, <i>JADE</i>, that allows comprehensive simulations of the complete life of hot planets. The <i>JADE</i> code dynamically determines the internal structure of a planet around its star to capture the impact of evolutionary processes such as the erosion of its atmosphere, the variation of the stellar flux, or the alteration of its orbit under the gravitational influence of a distant companion. We tested the <i>JADE</i> code on flagship targets inside or at the fringes of the desert like GJ 436 b and surmise that their exciting properties can be naturally explained by <b>an interplay between eventful dynamical and atmospheric histories. </b></div><div><br></div><div>Accurate measurements of the orbital and atmospheric tracers are crucial to constrain our models. Our joint approach to understanding the past atmospheric and dynamical pathways, combined with the commissioning of new generation instruments, offers the possibility to open a new window on the understanding of the origins of the desert, and more broadly of planets in the temperate zone.</div>
[Poster PDF File]