Planning for the Scientific Exploration of Mars by Humans By the mepag human Exploration of Mars Science Analysis Group (hem-sag)
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HAB “lab” CapabilitiesAtmospheric gas/subsurface volatile laboratory capabilities include isotopic and trace gas analysis. Microscope for dust size, shape and mineralogy. Capability to receive and process daily meteorological data from concurrent orbiters. Issues Identified That Would Require Handling Prior to Human ArrivalDesign of easy-to-assemble mast equipment. Miniaturisation of instrumentation. Radiosonde balloon design, gas fill, and communications infrastructure. Planetary protection considerations for released radiosonde balloons. Nominal Deep Drilling Polar Reference MissionThe high scientific value of a mission to the polar regions of Mars is outlined in section 1.3. The polar regions pose unique technical challenges due to cold temperatures and polar night which may be somewhat offset by access to a ready supply of water and radiation shielding material (ice). The north polar dome is the proposed target for a first human polar mission. A deep drilling phase is described followed by traverse to lower latitudes for launch at the onset of polar night. This reference mission does not include explicit biology investigations related to access to ancient ice, or geology investigations related to crossing the NPLD, both of which are anticipated to be of high interest. Scientific Goals and ApproachScientific Goals and Approaches for Deep Drilling Polar Reference Mission are shown in Table 9. Table 9. Proposed Scientific Goals and Approach for Deep Drilling Polar Reference Mission
LocationSelecting a bore site would follow common practice on Earth where remote sensing and local surveys are used to investigate a site before a drill site is chosen. Important parameters are depth of bedrock, topography of bedrock (a drill site should be close to a divide to minimize flow effects), thickness of ice layers (thicker gives more sensitivity for a chronology), quality of ice layers (distortion, density, temperature), and accumulation rate and local meteorology (want to minimize highly variable locales and local effects in selecting a site for a baseline chronology). High resolution gridded aerogeophysical surveys are used to map these parameters on Earth (e.g., Morse et al, 2002). For Mars north polar dome site selection, extensive precursor orbital geophysical and laser altimeter survey would be required to localize the drill site as far as possible to make most efficient use of the human team once they land. High-resolution orbiter laser altimeter measurements over several seasons would aid in understanding surface accumulation. On arrival, limited in situ geophysical survey could be used to pinpoint a drill site, to avoid small-scale distortions and embedded pebbles, as far as these can be detected. Research Plan and ScheduleThe Research Plan and Schedule is driven by the limitations imposed by polar night. In the worst case of a site at the geographical north pole, the sun will be at or above horizon at cap dome for only 372 sols (vernal equinox: autumnal equinox Ls 0:180). For a 500 sol mission this would infer that landing or launch are either done in darkness or migration of the team to a lower latitude rendezvous with the launch vehicle would b required. In the schedule below, a traverse to lower latitudes is described on the understanding that it presents additional risk and challenge. First phase: set up/test (40 sols)Land on cap dome within 2 km of bore site as selected from precursor orbital surveys Site selection: 30 sols
Set up and test of deep drill: 10 sols (4 people) Second phase: drilling (22 0sols)Figure 17 shows a timeline for EPICA deep drilling at Dome C. Figure 18 shows a timeline for an EPICA associated surface campaign.
Figure 17. Depth days at Dome C (Augustin and Antonelli, 2002). 
Figure 18. Timeline for a 2-month campaign for in situ surface heat and mass balance experiments associated with EPICA polar coring (Van de Broeke et al, 2002). Third phase: grand traverse (200 sols)Leave drill rig in situ and traverse NPD scarp southwards to rendezvous with launch vehicle for depart. Emplacement of additional seismic sensors with baseline of 500 km. Investigation of sites of biological and geological interest. Vertical Mobility RequirementsVertical mobility requirements for a Mars Polar dome core are:
Reviews of terrestrial deep drilling techniques can be found in NSF ICWG (2003b) and Bentley and Koci (2006). Tethered mechanical deep drilling remains the most popular technique on Earth (NSF ICWG, 2003b). These systems have a Bottom Hole Assembly whose weight relates to length of the core section and includes the weight of the core section to be raised to the surface. For a 3.5 m section, the BHA mass is ~200 kg, e.g., EPICA. Maintaining core quality still remains challenging (NSF ICWG, 2003a). However, extraction of an ice core on Mars may not be necessary from a science requirements perspective as Continuous Flow Analysis (CFA) is becoming increasingly used for analysis of ice core composition (Svensson et al, 2005). In this case the core is melted and a continuous flow of meltwater is analysed, giving high spatial resolution. Thermal drills can generate meltwater directly which could be pumped out of the drill hole under pressure along heated tubing to analysis instrumentation. Borehole instrumentation captures the stratigraphy while isotope and dust grain analysis are done from the meltwater. Atmospheric inclusions can be captured through control of pressure in a surface reservoir to allow dissolved gases to collect. Visual survey of the core stratigraphy can be achieved via a down borehole multispectral imager/microscope (Carsey et al, 2003). Thermal drill developments for Mars polar work have already begun (Cardell et al, 2006). High power would be required for a deep drilling mission — of around 1Wm-1 to keep the tether from freezing, with potentially multi-stage pumps to lift the meltwater from the hole. An insulated tether would be around 100 kg/km. Power required to drill and heat flow lines would be very challenging at depth — one possibility would be an RTG device in the bore-head. (personal communication, Michael Hecht and CHRONOS team). 
Figure 19. Thermal drill from Chronos Scout mission concept (Hecht and Chronos team, 2006). Horizontal Mobility RequirementsTo site drill rig – 2 km distance
Science Capabilities RequiredRequired scientific capabilities are shown in Table 10. Table 10. Science Capabilities Required.
Hab “Lab” CapabilitiesContinuous Flow Analysis equipment (pressurized and temperature regulated)
The laboratory would need to be sited in the near vicinity of the drill to minimize the transport of cores or the distance of flow tubing to be heated. Sample Return RequirementsDust collected from within the core would be of high scientific value to return to Earth for analysis. Could be subsampled, with samples only returned from significant lag deposits. Issues Identified that Will Require Handling Prior to Human ArrivalFeasiblity of a mid-length mission at the north polar cap
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