Transmission Spectroscopy of Super-Earth GJ 1214b With HST WFC3: Flat Spectrum Consistent With High-Altitude Clouds or H2O-Rich Atmosphere at 1.1-1.7 Micron

This study investigates transmission spectroscopy of super-Earth GJ 1214b using HST WFC3 at 1.1-1.7 micron to constrain atmospheric composition and distinguish between high-altitude clouds and H2O-rich atmospheric models within the context of exoplanet science and observational astronomy, an area of growing scientific importance given its implications for JWST GJ 1214b follow-up atmospheric characterization planning, cloudy atmosphere detection strategy for super-Earths, and mean molecular weight inference from HST flat-spectrum super-Earths. Using HST WFC3 G141 grism transit spectroscopy (6 transit visits, 12 orbits each), custom RECTE charge trap correction pipeline, systematics removal by Gaussian Process regression, and model comparison (flat/cloud, H2O-rich, H2-He) by Bayesian evidence, we examine atmospheric transmission spectroscopy detecting differential absorption of starlight at wavelengths matching molecular absorption bands (H2O at 1.38 um, CO2 at 1.60 um); flat spectrum indicating either high-altitude aerosol/cloud deck suppressing molecular features or a high mean molecular weight (H2O-dominated) atmosphere with smaller scale height reducing feature amplitude in 6 HST transit visits of GJ 1214b (M dwarf, V=14.7, transit depth 1.4%, period 1.58 days) from Cycle 20 GO-12473; 72 HST orbits total; spectral bins: 18 bins x 0.033 um from 1.1-1.7 um drawn from HST Space Telescope Science Institute data archive (MAST); WFC3 G141 grism at 1.1-1.7 um wavelength; reduction at Northern Plains Observatory with custom Python pipeline and GP systematics (george package). Results indicate that flat transmission spectrum consistent at 1.1-1.7 um; H2O absorption feature amplitude <84 ppm (3-sigma upper limit); Bayesian model comparison: flat/cloud model 48x more likely than solar-composition H2-He; scale height H < 180 km (implying mean molecular weight > 4 g/mol) (p < 0.001), with H2O feature <84 ppm; cloud model 48x more likely; scale height H<180 km; mean mol. wt >4 as the primary quantitative benchmark. Concordance between primary and confirmatory measurement approaches exceeded 93%, validating the analytical framework. These findings contribute empirically to exoplanet science and observational astronomy and carry actionable implications for the design of programs and policies targeting JWST GJ 1214b follow-up atmospheric characterization planning, cloudy atmosphere detection strategy for super-Earths, and mean molecular weight inference from HST flat-spectrum super-Earths.