  We present a study on the spatially scanned spectroscopic observations of the
transit of GJ 1132 b, a warm ($\sim$500 K) Super-Earth (1.13 R$_\oplus$) that
was obtained with the G141 grism (1.125 - 1.650 $\mu$m) of the Wide Field
Camera 3 (WFC3) onboard the Hubble Space Telescope. We used the publicly
available Iraclis pipeline to extract the planetary transmission spectra from
the five visits and produce a precise transmission spectrum. We analysed the
spectrum using the TauREx3 atmospheric retrieval code with which we show that
the measurements do not contain molecular signatures in the investigated
wavelength range and are best-fit with a flat-line model. Our results suggest
that the planet does not have a clear primordial, hydrogen-dominated
atmosphere. Instead, GJ 1132 b could have a cloudy hydrogen-dominated envelope,
a very enriched secondary atmosphere, be airless, or have a tenuous atmosphere
that has not been detected. Due to the narrow wavelength coverage of WFC3,
these scenarios cannot be distinguished yet but the James Webb Space Telescope
may be capable of detecting atmospheric features, although several observations
may be required to provide useful constraints.
