19 September 2017

Sol 1821: Heading for Half a Million Laser Shots

Posted by Ryan Anderson

Communication ties our lives together. If phone or internet service goes out in our area, sometimes we have to put our lives on hold for a few minutes or a few hours. The same is true for Mars operations. Yestersol Curiosity missed its ‘phone call’ from Earth due to a small issue at one of NASA’s Deep Space Network stations. We were aware of the issue yesterday, but we went ahead and completed the operation plan in case something would change at the last minute, but no dice. So today we plan to uplink exactly the same plan. Yestersol‘s plan is described in the blog for Sol 1820.

Of special note, ChemCam‘s observations will carry it past the half million mark for the number of laser firings on Mars. We receive a spectrum with each laser pulse, so these all represent a huge amount of critical data on Mars compositions. Fortunately, ChemCam‘s laser should last a while longer. Based on ground testing, we hope for at least another half million shots.

In some of my public talks, I joke about the initial media reaction to shooting the laser on Mars. We tell reporters that the ChemCam instrument ‘zaps’ rocks on Mars. However, sometimes the media edit this to sound a bit more engaging, writing that the rover ‘blasts’ rocks on Mars. The latter word can have much bigger connotations, like an explosion. In fact, at the time of the landing, we found a doctored picture on the internet showing ChemCam‘s laser beam eliciting a large explosion on Mars, with a fireball and debris cloud. In many of my talks I show this picture, which always brings a good laugh.

In reality, ChemCam makes only very small pits in the rock, well under a millimeter across. The RMI image shows the pits made in some of the softer rock we encountered a week ago on target ‘Sasanoa’. This image is only 5 cm (2 inches) across. Several years ago we used MAHLI to make a short video of the LIBS plasma on Mars (see video link).

When I think about these tiny traces that the rover leaves behind, I wonder if someday humans will follow the trail of this rover. Perhaps they will look for wheel marks, drill holes, and laser pits, a bit like we look for wagon-wheel ruts along the old Santa Fe Trail that brought 19th century settlers into the American West, or like we look for asphalt remnants of Route 66, the early- to mid-20th century highway from Chicago to Los Angeles.

Written by Roger Wiens, Geochemist at Los Alamos National Laboratory