Arc de cube

 
It is the year 207X. Strange cubes have been discovered in the outer solar system. They are smooth and reflective, and bigger than anything humans have sent into space.
Probes and rovers were sent but destroyed before they got to the surface by the interference around the cubes. An expedition crew was sent and disappeared too.
Everybody on earth is following the mystery. What is it? How is it here?
*Who* put it here?