Is it a Martian craft photographed by Curiosity on Mars July 28, 2013!
The photo in question that interests us here. It was taken on July 28, 2013, and posted on the official website July 29, 2013. The details of the photo are: Rear Left Hazcam B, SOL 347. I circled in black the "THING" and I enlarged . . .:
The photo is shown here on the official website:
ANOMALY ON MARS: PHOTOS: