This has already been argued back and forth. It's definitely not wet as in moist with liquid water (the temperature and pressure are too low). The lunatic fringe have been going ad nauseum, "Look it's wet, look it's wet, look it's wet...." like mindless parrots. Because of their damaged mental condition, they can't absorb the information about the temperature and pressure.

Why does the regolith look like it's wet? Either it's some kind of electrostatic effect or weird chemical adhesion. Mars is chemically diverse, bone dry (no liquid water on the surface) and has hard UV light reaching the surface. This provides ample opportunity for weird chemistry that is largely beyond our everyday experience.

Gary