Unknown substance hits vehical window and disappears without damage.Unknown Object Report November 9, 2015. About 15:00 Towson, Maryland 21286 About three o'clock, PM, on Monday, November 9, I was driving south on Providence Road in Towson, Maryland, Baltimore County.About 50 yards south of Hampton Lane, I noted a strange white light out of the corner of my left eye.I turned my head to better see what the white light was. As I did, the white light became the size of a basketball. The white light slammed into the driver's side door window. This was accompanied by a sound similar to hitting a strip of grooved pavement, but only on the driver's side.As I glanced at the white substance (or sphere) that had hit the window, I noted that it also spread leaks of white substance on all sides of it. It looked like a water balloon does when it hits something solid. I sounded like a beach ball hitting.This took no more than a second or three. I am not sure. My heart started to speed up, but I maintained control of the van; I slowed down so I could look into my side view mirror, looking for anything I might had hit. There was nothing there. I slowed further so I could see behind me and on the right side of the van, to the rear. There was nothing.I looked around me for other vehicles on the road, but saw none.It was a dry, sunny day; likely in the 70s.