Development of Crushing and Sieving Technologies for Use in Sample Preperation in Mars Exploration

Introduction: Subsurface investigation is one of the fundamental aspects of exterrestrial exploration. [2] Two general methods of studying the subsurface include in situ instrumentation and remote sample evaluation. This research investigates methods to crush core samples and prepare them for in remote analysis. Specifically, this research develops methods to comminute a core sample or regolith to produce small particles which are subsequently sieved to separate particles smaller than 150μm (fines) for use in scientific study. Comminution technologies were evaluated on size, power, and effectiveness to reliably produce large percentage fines (particles of 150μm diameter or smaller) from a single core sample or an amount of regolith. Research was conducted to investigate whether or not the composition of the crushed fines varied from the composition of the original core sample. In addition, the power necessary to crush different types of rocks was evaluated. Once suitably crushed, samples were sieved to separate the fines from the larger crushed particles. On-going investigations will determine low energy approaches to sieving. In addition, the designed crushing, sieving, and material handling system will be evaluated in regards to contamination. The key metrics in system effectiveness are identifying stray particles from the equipment itself as well as cross contamination from between samples. Crushing Technologies: Size reduction, also called comminution, is the separation of a particle into two or more parts. This can be achieved in principle by changing a particle shape beyond certain limits such as pulling it apart (as in tension), pushing it in (as in compression), twisting it (as in torsion) etc. Many types of equipment exist that perform size reduction and they can be classified according to comminution process. In general, there are five distinct categories: compression, impact, tumbling, cutting and attrition [1]. Before deciding which of the types of equipment to use, it is highly important to clarify the nature of the task based on the size of feed, degree of size reduction required and the rate of comminution. In addition, further constraints on the selection of most suitable equipment might be imposed by environmental factors. In space applications, these factors will include power consumption, size, mass, and complexity of a crusher, which is often related to reliability with a more complex design having a large number of parts being more prone to breakage. Taking into account the above mentioned factors, a strong choice for a crusher for space applications (such as on the surfaces of extraterrestrial planets, and in our case Mars) will be a hybrid piston-die press / attrition mill. A main advantages were the fact that a large percentage of material type can be produced in very small sizes (at or below 150 microns), suitable for delivery to various instruments such as TEGA or MECA, and that product size range can be very narrow [1], and that the crusher could be used to give accessibility to unaltered surfaces. See Figure 1.