Burnt circle in field

I'm sorry but I don't know the exact date, or even year, because this happened in my youth. (The 70's}   We lived by a cornfield and the corn was still green, so it must have been some time during the summer.  This happened in Yorktown Indian, right beside walnut street, a few miles out side Muncie, about 40 miles from Indianapolis.  I remember that my parents would invite my grand parents over to watch the strange lights and vehicles in the sky.  I remember seeing a few cigar shaped objects in the sky my self, but this isn't the main part of my sighting.  As a kid the neighborhood children and myself would play in the cornfields.  Most of us knew about the lights, but being young we really didn't think much of it.  What we did find that that struck us as odd was a circle burned into the corn, far out in the field.  It was as I remember a perfect circle of charred corn stalks about six inches wide, and the circle was about fifteen to twenty feet across.  The corn was pressed flat, as was the unburned corn inside the circle.  We knew the field pretty well and there was no farm machinery that went through the field during those summer months.  Out side the circle were sets of footprints that led out of the circle, but not very far from it then back to the circle.  What we found so unusual about them to us was that they were maybe 4 to six inches deep, with no tread marks, the bottom of the prints were flat with no tread that would be on a normal shoe or farmers boot.  On the surface of the footprint in the dirt was something that looked like green moss.  There were no tire marks leading to or away from the circle.  The soil wasn't soft, we didn't leave prints this deep, while we ran and played in the field, and that's what we found odd also.  I brought my mother out to the site so she also witnessed it.  She didn't know what to make of it ether.  My older brother was one of us kids that saw it also.  There are no military bases in the area, or even a airport of any size, so I don't think it was some "government project".  As far as I know the field is still there, and Yorktown is a very small town sleepy farm town, so I don't think anything has been built over the area.  If needed I can locate the other people that I knew at the time to verify the story, (the other children, by brother, and mother.  
Thanks for Listening,
((name deleted))