Written by John Schutt, private contractor...(Click here to return to: Field Updates)
Written by John Schutt, private contractor...
DRILLEX - The Drilling Experiment at Haughton Crater
A drilling experiment was part of series of research programs included in the Haughton Mars 98 project conducted at the Haughton Impact Crater during June-July 1998. The experiment is designed with two major objectives in mind; drill into and obtain continuous core samples of various rock units within the crater to recover a history of the post-impact geologic record and evaluate drilling technology for similar applications on Mars.
The lake sediments of the Haughton Formation are the only record of the Miocene (23 million years ago) in the entire Arctic. The sediments consist of layers of silt and mud that filled the crater and contain a diverse floral and faunal record. Thus, systematic sampling can yield unique perspectives on an important geologic setting. The lake presumably began infilling the crater immediately after crater formation. Latent heat from the cratering process may have resulted in hydrothermal alteration of sediments near the base of the unit. Soot derived from the vaporization of the impactor, or from other causes such as forest fires, may have washed down early in the sedimentary cycle and been preserved in the lowermost strata. Our goal was to extract a long, continuous core from a section of the Haughton formation for detailed analysis and to core near the base of the sediments and to penetrate into the breccia if possible.
Lakes existed on Mars in the distant past and sediments fill many of the craters. When exploration teams arrive on Mars they probably will be taking along a small drill with which to drill and sample the lake sediments there. Why? The lake sediments may have been places where, if life existed at all on Mars, there might be some record of its existence. Water may be present in the frozen subsurface. With water on Mars, human exploration of the surface of that planet becomes much more feasible. We are in the early stages of testing the tools and equipment for such a drilling program.
Drilling Equipment
The drill that was used is the JK Smit GW-15 that has been significantly modified by Salisbury & Assoc., Inc. The power source is a 10 HP 2-cycle gas engine. The drill is light weight and extremely portable and is mounted on an aluminum skid frame on which two boxes or agritainers are placed. Normally these agritainers hold water and drill mud and provide the reactive force and torque resistance. Since we did not need drill fluids, we used sand bags filled with local materials and placed them in the boxes for weight. Because we were using coring augers, we utilized a gear reduction unit to generate the high torque and low RPM requirements. The gear reduction unit is capable of producing around 300 ft-lbs of torque at 150 rpm
The entire drill disassembled and all equipment readied to move in 20-30 minutes and can be moved to another drill site in three trips with the ATV and trailer. Another 20-30 minutes is required to assemble the drill and make it ready to begin drilling
We were provided with a wide variety of coring and sampling equipment by the U. S. Army Corps of Engineers, Cold Regions Research and Engineering Lab.
Results
Seven 3” auger holes were drilled at Haughton Crater. A total of 96 feet were drilled. The total length of core recovered was 80.3 feet (24.5 meters). Three holes, AH98-1-3, were drilled in the Haughton Formation with the goal of acquiring a stratigraphic section for detailed study. The holes were drilled so as to hopefully intersect overlapping units common to each hole assuming a <5 degree dip of the strata thereby providing an uninterrupted composite section.
Holes AH98-4 and 5 targeted the base of the lake sediments and the contact with the breccia. Hole AH98-4 was abandoned at 3.08 meters (10.1 feet) when a pebble or cobble was encountered. Hole AH98-5 intersected the breccia and was advanced approximately 2 meters (6 feet) into the breccia. It is not known, until the sample has been analyzed, whether or not this is reworked breccia or pristine material. Hole 98-6 started out in possibly reworked, pebbly lake sediment material but soon entered into possibly reworked breccia material. Hole 98-7 was abandoned before the contact with the breccia was encountered due to breakage of the lever arm on the driving head of the auger barrel rendering the CRREL augers inoperable.
Conclusions
The limited program of drilling at Haughton Crater produced high quality, undisturbed core of a variety of material suitable for chemical and petrographic analyses. The drill is obviously not suited to a drilling program on Mars because of the extensive manual labor required to produce results. A highly automated drill would be required in that case. However, the results of the DRILLEX indicate that the CRREL coring auger system is a strong candidate for shallow drilling of fine grained ice-rich and ice-poor lake sediment on Mars.