Friday, 7 June 2013

How does a rover on Mars take a selfie?

Image credit: NASA/JPL-Caltech/MSSS
Doesn't this picture look like Curiosity is posing? It looks like someone is standing there taking a picture of it on Mars.  But there's no one else there. No wonder the conspiracy theory folks still have stuff to write about, the whole mission must be done from a secret studio in Area 51!

It actually takes a lot of work to generate this image.  It is really a mosaic of a dozen or so pictures, stitched together to come up with this illusion of a posed selfie.

Curiosity is well into its minimum 2-year mission on the planet Mars, looking for evidence that Mars has had, in its history, habitable zones.  These are areas under rocks, in fissures, or in ancient streams where liquid water would have existed and life, probably in the form of bacteria, could have thrived.  On Earth, pretty much anywhere there is liquid water and a source of energy, there is life.  Why would it be any different on Mars?

Curiosity has a number of cameras on board.  These cameras help it navigate, take super close-ups of rocks, take big panorama shots, and the cameras even help it aim its laser for science experiments.  One of these cameras is on the end of its robotic arm, and that's the one that snapped a number of images that were stitched together to form this picture.

But why can't we see the robot arm holding the camera?  That's where the Hollywood-style image manipulation comes in.  The arm and its wrist can take shots from different angles, enough angles so that it can be "erased" out of the component images but still have enough information left to stitch together an image of the rover without the arm in it.  In fact, this most recent mosaic was updated in May to include two drill-holes in the lower left quadrant that were not there when the first version of the selfie was published by NASA, 3 months earlier.

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