The surprising answer to How much more quickly does night come on Mars compared to Earth? Will it be easier to see Mercury there? is "up to two hours(!)" "…indicating that Martian dust extends very high into the atmosphere."
But I failed to ask how bright the twilight is. If it's longer but dimmer, then it might not interfere with seeing Mercury from Mars.
Question: How bright is twilight on Mars compared to Earth? Is there a plot of measured brightness (e.g. magnitudes per square degree or something similar) as a function of time, or at least for a few different times?