Cross in Circle Found On Mars By Opportunity NASA, Oct 2014, UFO Sighting News.

Date of photos:  7-12-2014 at 10:23 UTC
Mars Rover Name: Opportunity 
Location of discovery: Mars
Camera: Microscopic imager
Photo ID: Sol 3720 (5 photos)
NASA Source:

This unique formation was captured by the microscopic imager camera on the Opprotunity Rover. This little rover has out survived its mission and continued to do scientific research across Mars traveling a total of over 40km (25 miles). 

This microscopic image of a cross inside of a circle is unusual to say the least. It can be only one of three possible things. 

1st a tiny fossil creature. 
2nd a unique crystal formation. 
3rd micro technology

It may be a fossil of a micro creature, but the ring around it makes it unlikely. It has very few similarities to crystal, but again the ring causes me to rule that one out, however micro technology might be the most likely. Ancient tech, especially small would be very useful to regulate plants, animals and other ecosystems to create a controlled environment. Sure Mars is dry and barren, however NASA Chief Charles Bolden said in the UK this week that "Mars did have life on it and may still. Ancient micro tech would explain such an advanced world, far beyond our own. SCW