What if crop circles were just that species' way of leaving a calling card? -- Anon Guest
When tumbling along uncharted byways of Space, it's considered polite to leave something in the way of a marker. A tag, a sign that you were there. A temporary message that will soon be absorbed by nature, lasting just long enough for others who may follow to see... I was here, or, I'm headed this way. All the better for finding your way back if other avenues are not available.
The system eventually known as Sol was an especially problematic for having temporary exits from Hyperspace and no followup entrances that did not lead down a thousands-year temporal trap. Otherwise known as a one-way wormhole. Sol 3, being the only planet with a surface mutable enough to mark and stable enough to retain said mark for a passage of months, is often selected as a place to leave a mark.
Terrans never understood the Standard Marking System, and never decoded it before their meeting with the Allied races. It is a fortunate thing, since some marks beyond the simple circle or set of circles are... of a dubious nature. More than one roaming cogniscent has left an image of their own genitalia in a monoculture field. Others...