Mystery puddle

Son had first day of college today. He's a commuter. He's had his license since last October, but he never really drove much with gas being expensive and his not having reasons to go places.

He drove to orientation weekend events and had no problems, but today while J and I were doing our evening walk, I noticed a puddle beneath the car.

Hopefully, it's nothing. I drove around the block and such. Brakes worked and I didn't notice anything, so I'm a little puzzled. I put cardboard under the area I saw the leak. 

Unnecessary stress, but being a parent is such.