Is this something to worry about? 2000 Ford Crown Vic (Police Interceptor)

Is this an issue? I never noticed it before, we stopped for gas and heard a gasping sound, looked under the hood and saw this not turning as fast as the rest of the other pulleys..

Any mechanics out there have some ideas for us on this?

Model: 2000 Ford Crown Vic (Police Interceptor)

Thanks for your help