Green Fireball in connection with Possible Abduction or VisitationI would like to preface this report by drawing attention to the fact that I have a training in Physics and am currently working towards a PhD in the physical sciences.This is an incident which has long deserved a report with the national UFO reporting center, but I have had a great deal of anxiety regarding the sighting as it involves what I believe to be an encounter with extra-terrestrial beings later that evening.I was travelling on a cross country trip to the west in Iowa on I believe (from photos taken from this trip) to be US Route 30. While travelling, I saw a large Emerald Green Object alight in the western sky, about 10 degrees altitude above the western horizon. From my estimation, the apparent astronomical magnitude of the object was in the range of -10 (full moon is approximately -12.94). This was by far the brightest object in the sky at the time of the sighting.Furthermore, the object (or the green light emitted by the object) was spherical.The object was momentarily stationary (1-2s), and thence proceeded to move rapidly towards the North. The object traversed about 100 degrees azimuthal angle at a rate of 12-15(degress/sec), and then rapidly faded in magnitude until it was no longer visible. The trajectory of the object seemed both too low, and too slow to be of meteoric origin. From my estimation, this object was well within the troposphere for the entire course of its trajectory.As the object traversed the sky, it left a trail of white flecks of light behind it. The trail was linear, and about 15 degrees of azimuth in length and constant in magnitude. There was no sound accompanying the traversal of the object.I was quite shaken by the incident, and pulled off at a local gas station. I had taken many photos of the gas station in attempt to recall the location of the object.With the sighting, I strongly recall the thought "I should not have seen that." After driving from Iowa south into Missouri, I pulled off to take a few hours of rest in the car. The car was parked on the side of a small county road on a bridge over the Nodaway river (which is a tributary to the Missouri river). The time was about 2AM.At this point, I was attempting to get some rest, when I perceived a white light around the vehicle along with the silhouettes of three extra-terrestrial beings. The beings were about 4ft tall as measured relative to the window of the vehicle. One of the beings was in front of the car, and two were on the left side (I was in the drivers seat of the car). I had the sense that there was a fourth being near the back of the vehicle.I then recall "waking up" and the time was 6AM. I was very tired, and sweaty, as if I had exerted myself physically during the previous four hours. I a vague recollection of what transpired during this four hour period. I can unequivocally say that the perception of the beings and the light was not a dream. This is corroborated by the fact that I have a detailed memory of this experience.I will be happy to work with the National UFO reporting center in order to shed further light on the UFO sighting itself, as well as other events in connection with the sighting including details left out of this cursory account.