The physical mechanisms governing the greenhouse effect—specifically molecular absorption of thermal radiation by gases—are well established by spectroscopic measurements and satellite observations of radiative forcing.
The claim states that greenhouse gases are prevented from escaping into space by gravitational retention and molecular absorption. The retrieved papers consistently support the principle of molecular absorption of radiation by greenhouse gases (such as CO2 and CH4) as demonstrated by satellite measurements of outgoing longwave radiation and radiative transfer models. While planetary retention involves gravity, the primary mechanism of greenhouse gas forcing documented across multiple studies is molecular absorption in the atmosphere. Therefore, the claim is supported by the literature.