How did this unusual Martian rock form? The atypical two-toned rock, visible in the lower right of the above image [ http://origin.mars5…], was photographed a few days ago by the robotic Spirit rover [ http://science.hows…] currently rolling across Mars [ http://en.wikipedia…]. For now, the environmental processes [ http://humbabe.arc.…] that created the rock remain a matter of speculation [ http://www.nasa.gov…]. Finding unusual rocks is not unusual for Spirit [ http://antwrp.gsfc.…] or its twin rover Opportunity [ http://antwrp.gsfc.…], however. Over the past two years, for example, the rovers have unexpectedly discovered very small gray pebbles [ http://antwrp.gsfc.…] dubbed blueberries [ http://www.whfoods.…], and a rock out in the middle of nowhere [ http://antwrp.gsfc.…] now thought to be a meteorite [ http://meteorites.l…]. Having investigated alien terrain [ http://antwrp.gsfc.…] and having found clear evidence that part of Mars had a wet past [ http://antwrp.gsfc.…], the Earth-launched Martian rovers are now entering their third spectacular year [ http://www.jpl.nasa…] exploring the red planet.
