  We present the first spectroscopic estimates of the chemical abundance of M
dwarf stars in a globular cluster (GC), namely 47 Tucanae. By exploiting
NIRSpec on board the James Webb Space Telescope (JWST) we gathered
low-resolution spectra for 28 stars with masses in the range ~0.4-0.5 solar
masses. The spectra are strongly affected by the H2O water vapour bands which
can be used as indicators of the oxygen abundance. The spectral analysis
reveals that the target stars feature a different O abundance, with a
difference of ~0.40 dex between first and the most-polluted second population.
The observed range is similar to that observed among red giant stars. This
result reinforces previous findings based on the analysis of photometric
diagrams, including the ``chromosome maps'', providing a first, and more
direct, evidence of light element variations in the M dwarfs' mass regime. The
observation that the multiple populations, with their variations in light
elements, exhibit the same patterns from the lower main sequence all the way to
the red giant branch further strengthens the notion that multiple stellar
populations in globular clusters formed in a series of bursts of star
formation.
