The first Mars Observer was launched in September 1992, and expected to send back data on geological and climatic conditions. The probe was reported lost on the 21st August 1993. 

Since 1979 some highly qualified investigators have studied, extensively, a number of photographs taken by the 1976 Viking Mars mission in the Martian region called Cydonia. These photographs show one side of an enormous human like face. At first glance the obvious conclusion is that this is a trick of shadows and lighting; but computer enhancement, it seems, shows clearly that the other half of the face is also there. There are also several pyramids in a cluster, so one is bound to ask, why here and nowhere else? The face was at longitude 9.52 degrees and latitude 40.89 degrees in Cydonia. The facial features were approximately one mile wide. The picture was enhanced using a digital computer. 
 
   

Some investigators feel that some of the features could be artificial. Many reputable scientists have called for further investigation by NASA 

For more details on this case see UFO AFRINEWS No. 15