yes, it looks that way, that the surge of current exploded the gas in one cell. Maybe the electrolyte level was too low and it overheated. If that was the case then i was remiss in not maintaining the battery properly.

and yes, now i am more wary about anyone being near the battery when the car is being started and also when it is being jumpstarted. Previous to this experience, i did not pay much attention to it, and saw the thing as something inert - an appliance, if you will.

well, the battery brand was Benz (probably OEM), and hopefully this is just a fluke and does not happen to all of you benz owners ...