On Curiosity's journey at sol 735 we came across these images from NASA.
Are we looking at an ancient alien device on Mars ?
Did NASA use fake sand to cover up something ?
Have we found an anomaly with actual writings or symbols on ?
And what are we looking at 700 sol's later at sol 1428-1429 ?
Have a look at the original images directly from NASA's website, and explorer the Gigapans.