  MassSpec, a method for determining the mass of a transiting exoplanet from
its transmission spectrum alone, was proposed by \citet{dew13}. The premise of
this method relies on the planet's surface gravity being extracted from the
transmission spectrum via its effect on the atmospheric scale height, which in
turn determines the strength of absorption features. Here, we further explore
the applicability of \textit{MassSpec} to low-mass exoplanets -- specifically
those in the super-Earth size range for which radial velocity determinations of
the planetary mass can be extremely challenging and resource intensive.
Determining the masses of these planets is of the utmost importance because
their nature is otherwise highly unconstrained. Without knowledge of the mass,
these planets could be rocky, icy, or gas-dominated. To investigate the effects
of planetary mass on transmission spectra, we present simulated observations of
super-Earths with atmospheres made up of mixtures of H$_2$O and H$_2$, both
with and without clouds. We model their transmission spectra and run
simulations of each planet as it would be observed with \textit{JWST} using the
NIRISS, NIRSpec, and MIRI instruments. We find that significant degeneracies
exist between transmission spectra of planets with different masses and
compositions, making it impossible to unambiguously determine the planet's mass
in many cases.
