While driving West from Placerville, CA on HWY 50 toward Sacramento, CA @ approximately 5:50 a.m. - Sept. 12, 2014, I noticed what I thought was a helicopter with it's spotlight on. Seconds later the "beam of light from spotlight" became much wider and longer. What I thought was the "spotlight" became much, much brighter, almost pulsating, then POOF it disappeared. From the moonlight you could see whatever was left was spiraling upward, then it disappeared as well. What was left was a huge misty, vapor cloud. It lasted long enough for people to start pulling off the highway to get a better look. I am certain I am not the only driver that day thinking "Oh great, we get to drive under that mysterious vapor cloud as it dissipates and falls on us"! WHAT THE HECK WAS IT? KCRA - NBC affiliate Channel 3, Sacramento CA, ran a story and interviewed several witnesses who photographed and videoed it on their phones. NO ONE can tell us what it was. Thank you.