 EVALUATING CORE CONTAMINATION DURING DRILLING UNDER MARS-LIKE CONDITIONS.  Goordial, J. 1, Zacny, K. 2, Whyte, L 1., Spring, J 2. 1 McGill University, Macdonald campus, Quebec, Canada. 2 Honeybee Robotics, Pasadena, CA (zacny@honeybeerobotics.com).  Introduction: Samples which will be of scientific interest for a future Mars mission (such as the Mars2020 mission) will include rock samples which can only be formed in the presence of water. These samples will be of interest for looking for both geochemical and organics analysis, as well as signs of extinct (or extant) life, and as such contamination is a concern. In future missions, in particular those going to regions of special interest, regions within which terrestrial organisms are likely to replicate [1], knowledge of cross and forward contamination will be critically important. It is extremely difficult to completely decontaminate and sterilize all spacecraft surfaces prior to heading into space [1], and the Mars 2020 Science definition team acknowledges that this is practically impossible [2]. When the sample acquisition system is the same as the sample delivery system as was the case for both Phoenix and Curiosity, knowledge of how and the extent to which instrumentation may contaminate samples is critical for downstream scientific analysis. Additionally important in such regions of special interest are planetary protection concerns - for example drill cuttings that get left behind but that are in abrasive contact with the sampling system.   The goals of the present study were to determine the likelihood of microorganisms transferring from drilling surfaces (drill bit and teeth, core breakoff tubes etc.) onto acquired samples under Mars-like atmospheric pressure conditions.  The rocks chosen for this study: travertine, gypsum, and kaolinite,  are formed in the presence of water, and are representiave of samples likely to be targeted during the Mars 2020 mission.  Drill Testing methodology:  All tests were conducted using Honeybee's Rotary-Percussive drill called SASSI [3]. The drill was mounted inside a Mars vacuum chamber. Mars conditions included 7 torr pressure and room temperature. Chamber was purged with N2. We used rotary-percussive coring bit with four carbide cutters. The bit was designed to capture 1 cm diameter and 6 cm long core, hence all drilling tests were done to 6 cm depth. The outside bit diameter was 1.6 cm. The bit rotation speed was kept constant at 300 rpm.  Microsphere application and analysis: To test microbial contamination, Fluorescent latex microspheres (Fluoresbrite yellow-green carboxylated microspheres; Polyscience, Inc., Warrington, Pa.) of 0.5 um and 0.05 um diameter were used as microbial tracers to monitor potential contamination during drilling of rock samples. Using fluorescent microsphere was easier from handling stand point than using E-Coli in prior work [4]. A solution of fluorescent microspheres was made by adding 250 ul of each stock solution of microspheres to 500 ul of acetone. Microspheres were applied evenly with a pipette to entire 5 cm length of the inside of the break off tube (200 ul solution), and to the inner 2 cm of the drill bit and teeth (50 ul solution) delivering a total of 9.1 x 10 13 microspheres. The microsphere solution was dried with a blow dryer prior to drilling. Visualization of the fluorescent microspheres on core samples was performed using a portable UV light source (320 nm) prior to processing the samples. Processing for microscopy was performed by making a lateral cut across the core to create a clean face, and then sampling the core from the center in 2 mm increments outwards to avoid transfer of spheres towards the interior. The sampling knife was washed with acetone between sections. Microsphere distribution into new faces created by breaks in the core from drilling was also examined. Outer and inner drill cuttings were collected. A volume of 75 ul of crushed rock for each section was liquefied with 1 mL water, homogenized and dried onto an area of 1 cm 2 onto microscope slides.  Microsphere distribution was quantified using a fluorescent microscope. For each sample ten random fields were counted.   Figure 1. Fluorescent microsphere distribution visualization under UV light on a travertine core drilled under atmospheric conditions (top) and under vacuum (bottom). The top of the core is on the left hand side.  Core Drilling testing results: Data in Table 1 and 2  show pertinent drill parameters and test conditions in travertine rock. Three tests were conducted at 760 torr and 7 torr, each. The data shows that drilling power and energy was higher at Mars conditions while core quality was lower (that is the core was more broken up). It is believed that this is due to changes in coefficient of friction between cuttings and drill and changes in cuttings friction angle. At Mars vacuum, friction between soil/rock andfriction angle is lower [5].This caused the cuttings to flow into the bit (referred to as "powder" in Tables 1 and 2) as opposed to being augured out (referred to as "cuttings" in Tables 1 and 2).  Table 1. Drill test results: Earth conditions Test 1 2 3 WOB, N 33 30 40 ROP, cm/min 1.0 1.0 0.9 SE, Whr/cm 0.38 0.3 0.46 Core mass, g 10.7 11.5 11.4 Cuttings mass, g 0.49 0.5 0.74 Powder mass, g 0.14 0.01 0.16         Table 2. Drill test results: Mars pressure Test 1 2 3 WOB, N 34 37 42 ROP, cm/min 1.0 0.95 0.63 SE, Whr/cm 0.42 0.48 0.76 Core mass, g 10.7 10.8 10.5 Cuttings mass, g 0.12 0.01 0.47 Powder mass, g 0.55 0.63 0.29         Microsphere distribution: Direct visualization of the cores with a portable UV light showed that, in general, microsphere load was highest near the surface of the rock sample and lessened with depth into the rock (Fig. 1), as well as from the outside surface of the core into the center of the core (Table 3). This trend was also observed on the faces of cores where breaks during the drilling process had occurred; break faces at the top of the core had a higher microsphere load; the values were comparable to those observed on the outside or cores. Microsphere distribution varied between Mars/Earth conditions (Table 3), where cores drilled under Mars conditions generally had 1-2 orders of magnitude less tracer. Under both conditions, drill cuttings from inside the break of tube and from the outside of the drill bit/tube contained spheres with a similar load to those found on the outside of sample cores. Cuttings which are left behind would be a concern for planetary protection of sampling sites in the Martian environment.  Table 3. Microsphere distribution in travertine Depth along length of core Depth within rock Earth conditions* Mars Pressure* 0 cm  (top of core) 4-6 mm  (center) 1.2 x 103  5.7 x 101  2-4 mm  1.4 x 10 3 1.5 x 103  0-2 mm  (outer core) 2.1 x 103 1.4 x 103 2.5 cm  4-6 mm  1.8 x 10 2 2.5 x 101  2-4 mm  1.3 x 10 2 1.9 x 101  0-2 mm  3.9 x 10 2 1.8 x 101 5 cm  4-6 mm  5.8 x 10 1 0  2-4 mm  1.6 x 10 2 0.3  0-2 mm  2.9 x 10 2 2.5 x 101 Inner Cuttings  2.7 x 10 3 2.0 x 102 Outer Cuttings   1.4 x 103 3.0 x 102 *microspheres per ul volume of crushed rock. Conclusions: In general, 'microbial load' as inferred by microsphere distribution was less under the Mars conditions. Microsphere distribution on the outside of core samples was ~10 orders of magnitude lower than the amount of tracer applied to the break tube and drill bit. Important to note is that while the surfaces of instruments sent to Mars are unlikely to be completely sterilized, they would almost certainly not contain a microbial load as great as those used here (10 13 spheres). As such, this work demonstrates that the inside center of cores, towards the bottom of core samples are the least likely to be contaminated, and would be the best candidates for downstream life detection analyses. Special care will have to be taken in samples where fissures are introduced to the cores, which is demonstrated here to have a higher occurrence under Mars atmospheric conditions.  References: [1] Rummel, J.D., et al. (2014) Astrobio. 14 (11), 887-968. [2] Mustard, J., et al. (2013) Report of Mars 2020 sci. def. team. [3] Zacny, K., et al, (2013) AIAA Space Conference 2013-5410 [4] Zacny et al. (2006) Mars Society Conf, [5] Zacny, K. and Cooper, G. (2007) Geophys. Res: planets. 112 (E3)  Additional Information: This work has been supported by NASA PIDDP program. Thanks to P. Vaishampayan and K. Venkateswaran at NASA JPL for help and use of their fluorescence microscope.  
