  M dwarf stars are high-priority targets for searches for Earth-size and
potentially Earth-like planets, but their planetary systems may form and evolve
in very different circumstellar environments than those of solar-type stars. To
explore the evolution of these systems, we obtained transit spectroscopy and
photometry of the Neptune-size planet orbiting the ~650 Myr-old Hyades M dwarf
K2-25. An analysis of the variation in spectral line shape induced by the
Doppler "shadow" of the planet indicate that the planet's orbit is closely
aligned with the stellar equator (lambda = -1.7+5.8/-3.7 deg), and that an
eccentric orbit found by previous work could arise from perturbations by
another planet on a co-planar orbit. We detect no significant variation in the
depth of the He I line at 1083 nm during transit. A model of atmospheric escape
as a isothermal Parker wind with a solar composition show that this
non-detection is not constraining compared to escape rate predictions of ~0.1
Mearth/Gyr; at such rates, at least several Gyr are required for a Neptune-like
planet to evolve into a rocky super-Earth.
