We present new calculations of transit spectra of super-Earths that allow for
atmospheres with arbitrary proportions of common molecular species and haze. We
test this method with generic spectra, reproducing the expected systematics and
absorption features, then apply it to the nearby super-Earth GJ 1214b, which
has produced conflicting observational data, leaving the questions of a
hydrogen-rich versus hydrogen-poor atmosphere and the water content of the
atmosphere ambiguous. We present representative transit spectra for a range of
classes of atmosphere models for GJ 1214b. Our analysis supports a
hydrogen-rich atmosphere with a cloud or haze layer, although a hydrogen-poor
model with less than 10% water is not ruled out. Several classes of models are
ruled out, however, including hydrogen-rich atmospheres with no haze,
hydrogen-rich atmospheres with a haze of about 0.01-micron tholin particles,
and hydrogen-poor atmospheres with major sources of absorption other than
water. We propose an observational test to distinguish hydrogen-rich from
hydrogen-poor atmospheres. Finally, we provide a library of theoretical transit
spectra for super-Earths with a broad range of parameters to facilitate future
comparison with anticipated data.Comment: 33 pages, 21 figures, 3 table
