I think you misunderstood a bit. The circular symbol is not correlated to the landing sites in any way. It's just a example of the alien's writing system, which

I think you misunderstood a bit. The circular symbol is not correlated to the landing sites in any way. It's just a example of the alien's writing system, which large parts of the movie centers around deciphering. It's a pretty good movie, i can recommend watching it.