I can’t help it. When I see a drill I think of the dentist and all the boring my teeth have endured over the years. That high-pitched whine, the holes carefully excavated for fillings. The bill. Yet without the occasional trip to the dentist, our lives would be punctuated with much unnecessary suffering.
Curiosity will finally use its own drill in the coming days to gather a sample of rock particles for analysis at the Yellowknife Bay site on Mars. Scientists and engineers have taken great care to find the right kind of rock and best location for drilling. A nearly flat surface is a must for stability as is a fine-grained rock, that when ground up, will serve to clean the inside of the drill and its sample storage area. Rocks that look solid but could turn to mud under the pressure of drilling have to be avoided. Researchers don’t want to gum up the instrument.
The term “drill” is a bit misleading. The device is really a spinning chisel with a hammer-like motion that breaks up rock into powdery bits. The material is then augured up a hollow sleeve and into a small storage area. Rock from the first few drilling attempts will be used to clean the mechanism of any earthly contamination; later samples will be stored atop the bit and delivered to a particle-size sorter by extending the rover arm and letting gravity move the material. From there, it heads to the internal chem lab for analysis.
One other concern being addressed is how the day-night temperature change at Curiosity’s location affects how much pressure the rover’s arm can apply on the drill. Afternoon high temperatures are around the freezing point, while nighttime lows sink to -85 F. The wide swing in temperatures causes the rover arm, chassis and mobility system to grow and shrink about a tenth of an inch or a little more than the thickness of a quarter over the course of a Martian day (40 minutes longer than an Earth day).
While NASA doesn’t plan on leaving the drill bit in overnight, if it happens, engineers need to know what to expect as far as stress limits on rover hardware. That’s why mission control performed a “pre-load” test yesterday (Jan. 28) to find out how the temperature affected the pressure on the drill.
So many details to consider if we want our robot to live a long and productive life on the Red Planet. No wonder 400 scientists are involved in the mission.