THIS IS A COPY OF A NASA PRINT in my possession. It has this strange feature on it in the picture on the right. We can clearly see the letter "S". The size of it is not known, but it is rather big. It clearly looks like it is artificially created. Your guess is as good as mine, but maybe created by someone as a sign for us on Earth to see. It is clearly meant to be seen from above, just like the NASCA PLAINES in South America. It is too big to be observed from the ground. I found this picture in a book, and wrote to NASA in Houston to have a copy of the original Print. You should too.