  Over the last two decades, the discovery of exoplanets has fundamentally
changed our perception of the universe and humanity's place within it. Recent
work indicates that a solar system's X-ray and high energy particle environment
is of fundamental importance to the formation and development of the
atmospheres of close-in planets such as hot Jupiters, and Earth-like planets
around M stars. X-ray imaging and spectroscopy provide powerful and unique
windows into the high energy flux that an exoplanet experiences, and X-ray
photons also serve as proxies for potentially transfigurative coronal mass
ejections. Finally, if the host star is a bright enough X-ray source, transit
measurements akin to those in the optical and infrared are possible and allow
for direct characterization of the upper atmospheres of exoplanets. In this
brief white paper, we discuss contributions to the study of exoplanets and
their environs which can be made by X-ray data of increasingly high quality
that are achievable in the next 10--15 years.
