  Many of the confirmed short period super-Earths and smaller sub-Neptunes are
sufficiently irradiated for the surface silicates to be sustained in a
long-lasting molten state. While there is no direct evidence of magma ocean
influence on exoplanets, theory suggests that due to outgassing and diverse
evolution paths, a wide range of resulting atmospheric compositions should be
possible. Atmospheric contamination caused by the outgassing of the underlying
magma ocean is potentially detectable using low resolution spectroscopy. The
James Webb Space Telescope provides the necessary spectral coverage and
sensitivity to characterise smaller planets, including lava worlds. In this
light, we assess observability of outgassed silicates submerged in volatile
atmospheres on the edge of the evaporation valley. By placing a hypothetical 2
R${_\oplus}$ planet around a Sun-like star, we self-consistently model, in 1-D,
a wide range of potential atmospheric compositions, including thermal structure
and outgassing. We focus on atmospheres rich in H, C and N. We assess diverse
chemistry of silicates and volatiles, and what features of outgassed species
could be detected via emission spectroscopy using MIRI LRS. Results indicate
that even for substantial volatile envelopes, strong in infrared opacity, the
presence of silicates causes deep thermal inversions, affecting emission.
Similar to pure lava worlds, SiO remains the only outgassed species with major
infrared, 5 and 9 \textmu m, bands. However, even a small amount of volatiles,
especially of H2O and H-, may hinder its observability. We also find that the
C/O ratio plays a large role in determining the abundance of SiO. Detecting SiO
on a strongly irradiated planet could indicate an atmosphere with high
metallicity and a low C/O ratio, which may be a result of efficient interaction
between the atmosphere and the underlying melt.
