This post originally appeared on Jim’s Cleo Blog and is reproduced with the author’s permission.
What do front man for the Black Eyed Peas, Will.i.am, and ultrafast optical pulses have in common? They are both playing crucial role on the newest Mars rover mission. On August 28, Will.i.am’s song “Reach for the Stars” was the first musical composition to be transmitted to Earth from another planet, in this case from Curiosity, twelve days after its Seven Minutes of Terror landing, complete with state-of-the-art supersonic parachute and sky-crane. I’m still a bit shocked at this science fictionesque feat of impressive engineering seeming to border on hubris. Really, a sky-crane? Really?
While Will.i.am’s interplanetary music transmission is playing a critical role in science and engineering outreach as part of google+ and Lockheed Martin sponsored initiative SYSTEM (Stimulating Youth for Science Technology Engineering and Math), ultrafast optics is playing a critical role for analyzing the geology of the martian surface. On August 19, ChemCam, an instrument that is a part of the Mars Science Laboratory on board Curiosity, ablated part of a rock with ultrafast optical laser pulses and performed chemical analysis on the emitted plasma to determine rock and soil composition, a first for exogeology. Though the technique, laser induced break-down spectroscopy (LIBS), is almost as old as the laser itself, it has never been performed on another planet. What makes LIBS so useful for Mars exploration is that as an active remote sensing technique, no physical contact needs to be made with the rock or soil under test, including cleaning the sample area.
The previous Mars rovers required a rock abrasion tool to remove dust and outer layers to analyze the more interesting unweathered interior of rock and soil samples. On Curiosity, initial pulses “clean” the area and subsequent pulses create the plasma of interest whose spectrum is to be analyzed. For this instrument standoff distances can be as far as 7 m. The LIBS instrument has been combined with a Remote Micro-Imager (RMI) to give contextual information around the approximate 0.5 mm LIBS interrogation points in a single instrument called ChemCam. The figure below shows the precision of the laser system as well as the resolution of the Micro-Imager at 3 m stand-off. The choice to burn precision holes in the U.S. dollar and Euro (near Toulouse, France on the Euro map) is in homage to locations of the collaborating institutions Los Alamos National Laboratory, Centre National d’Etudes Spatiales, and Centre National de la Recherche.
Besides the ultrafast laser system, ChemCam is a goldmine of optical engineering and instrumentation. There is honestly something for almost any kind of optical scientist on this instrument. Details can be found both on the ChemCam website and in a review of the instrument suite (an easy geeky read which I had trouble putting down). The laser and imaging optics reside in the mast of ChemCam (the seeming periscope-like eye of the rover) and the spectrometers and supporting equipment live in the body unit. The mast and body are connected by optical fiber.