Bright green - blue sphere silently moving parallel to freeway.

Two friends and I were driving to Hobby Airport (Houston's 2nd commercial airport) heading southbound on the Gulf Freeway (I-45) from downtown. It was raining slightly and foggy. About one mile south of the I-45 and Loop 610 Interchange, almost at the Hobby Airport exit, we all three saw a bright green sphere that moved parallel to the freeway, about 150-200 feet from the ground. It didn't make any sound. The object was almost in the clouds or fog and it cast a bright green glow in the fog and clouds directly over it. The object then changed direction; it turned slightly left and crossed over the freeway, headed south-southeast (towards Clear Lake and the NASA headquarters). When it was on the other side of the freeway, we could also see a deep blue color on the lower 1/3 of the sphere, but the green glow was much brighter. It then disappeared in the clouds. In order to calm ourselves, we all assumed that this was a meteor or maybe an aircraft heading toward NASA that was partially obscured by the fog. This happened 10 years ago and I remember it as if it were yesterday. At the time this happened, all three of us were employed as clinical chemists at a major hospital located in the Texas Medical Center.