No tail of light like a meteor, just bursts of light from what seemed to be from deep space.

About 10pm May 28, 2012 looking nearly straight up in sky ( I live in Mesa AZ, USA) a little to North I saw a faint light that got brighter and went white to blue then faded to nothing took about 4-6 seconds. It got to about 25% of the size of the moon. Then about 5 to 8 min latter just a little to the East it happened again just not as big, but just as bright and it did not last as long. Any one else see it, can anyone tell me what it was.  Also, I saw the same thing last Wednesday night (May 23) in the North Eastern sky, this one was a little more orange.  But what caused me to write about it and search for an answer for what I was, each had no tall. It was just a burst of light.  Like in the meteor fall that leaves a tail showing the direction of the fall, these all had no tails, no streaks? What is it, anyone know?  
((name deleted))