  Reflection spectroscopy holds great promise for characterizing the
atmospheres and surfaces of potentially habitable terrestrial exoplanets. The
surface of the modern Earth exhibits a sharp albedo change near 750 nm caused
by vegetation - the red edge - which would leave a strong spectral signature if
present on an exoplanet. However, the retrieval of wavelength-dependent surface
properties from reflection spectra has seen relatively little study. Here, we
propose a new surface albedo parameterization capable of retrieving the
wavelength location of a priori unknown 'edge-like' features. We demonstrate
that a wavelength-dependent surface albedo model achieves higher accuracy in
retrieving atmospheric composition. Wavelength-dependent surfaces are also
generally preferred over a uniform albedo model when retrieving simulated
reflection spectra for a modern Earth analog, even for moderate signal-to-noise
ratios (S/N = 10) and Earth-like clouds. Further, the location of the modern
Earth's red edge can be robustly and precisely constrained (within 70 nm for
S/N = 10). Our results suggest that future space-based direct imaging missions
have the potential to infer surface compositions for rocky exoplanets,
including spectral edges similar to those caused by life on the modern Earth.
