The Curiosity Mars rover lived up to its namesake today, trying out a little amateur astronomy to catch the Mercury transit - and event that certainly cannot be viewed with the naked eye back on Earth.

This is the first transit - an event during which the silhouette of a celestial body can be seen passing in front of the Sun - ever observed from another planet. Not to mention that it was remarkably clear to see, despite the fact that the Curiosity rover is not equipped to be gazing at the sky.

The Curiosity rover was sent to Mars to observe the geology and chemical signatures of the Red Planet, and was only equipped with a low-definition (relative to available technologies) Mast Camera video instrument, perfectly adequate for taking in vast swaths of the Martian landscape at a time. The rover's "eyes" certainly were not designed to peer at the Sun.

Mark Lemmon and his colleagues from the Mastcam science team directed the rover to take an astronomy break anyways, purely for the sake of finding out just what a Mercury transit looks like from another planet.

"This is a nod to the relevance of planetary transits to the history of astronomy on Earth," Lemmon said in a statement.

He explained that Mercury transits - which are only visible by telescope from Earth - were used long ago to help measure the size of the Sun.

Scientists observed the event June 3, and described it as a fuzzy black dot traveling across the Sun's face. The very distant planet only fills about one pixel in the Mastcam video, but the transit itself is still very clear in nature.

Two larger and darker dots - sunspots about the size of the Earth - can also be seen through the Curiosity rover's "eyes," though they move only at the pace of the Sun's rotation and are outpaced by Mercury's silhouette.

A video of the Mast Camera observation of the Mercury transit was made available by NASA on June 10.


[Credit: NASA/JPL-Caltech/MSSS/Texas A&M]