Stoker Mars drilling SRR6

Drilling to Extract Liquid Water on Mars: Feasible and Worth the Investment: 

Drilling to Extract Liquid Water on Mars: Feasible and Worth the Investment Carol Stoker NASA Ames Research Center

Key Points: 

Key Points Water is the most important resource for supporting human exploration of Mars Drilling to liquid water is the most cost effective method for obtaining water on Mars Drilling to liquid water converges the goals of the human exploration program with the goals of astrobiology (water= life) A program to identify locations of subsurface water should be a key focus of the robotic Mars exploration program in the next decade Developing deep drilling technology for Mars should be supported by Code T

Slide3: 

Atmospheric water vapor 1-90 x10-6 m Ground ice >50% of total (soil + ice) poleward of 60o Hydrated minerals in soil 2%midlatitude average, 10% in enhanced areas Liquid water at depth (assuming it is there) Where is the water? Water is the most important resource for human exploration

Slide4: 

Deep Aquifer Dehydrated surface layer Ice saturated cryosphere Basement Rock 1-5 km 100’s m Global deep aquifer occurs if Mars is sufficiently water rich to saturate the cryosphere. Depth of liquid water varies with surface topography and latitude. Deep Subsurface Aquifer Predicted (Clifford, 1993) warm cold Vapor transport

Slide6: 

Shallow subsurface liquid water may exist at hundreds of locations Locations of Martian Gulleys : All poleward of 30o

Slide7: 

Heldmann and Mellon, Icarus 168, 2004 Latitude Latitude Depth Average Gulley depth is 200m below level surface Gulleys form on steep slopes. Maximum channel length is 500m

Slide8: 

• Typical surface temperature at latitudes which gullies form is << 0o C. • Geothermal lapse rate = dT/dz=q/K, where K=thermal conductivity q=geothermal heat flux. • K=I2/rc, where I is thermal inertia measured by TES. Gully locations have low thermal inertia. • Depth of 0o C isotherm consistent with Alcove head depths. Shallow melting depth due to low thermal conductivity material which exists primarily at high latitudes Gully formation model (Heldmann and Mellon, 2004) Aquifer Insulating soil layer

Is drilling to liquid water the best resource extraction approach ?: 

Is drilling to liquid water the best resource extraction approach ? From Meyer and McKay, Strategies for Mars a Guide to Human Exploration, 1996 Need a metric to evaluate resource extraction technology and system level designs for resource extraction systems

Slide10: 

Standard commercial drill uses drilling fluid to transport cuttings. Drilling fluid is biggest mass of system. On Mars could (possibly) drill dry or use liquid CO2 for cuttings transport

Challenges of Robotic Drilling on Mars: 

Challenges of Robotic Drilling on Mars Minimally-characterized environment Low power and mass budgets Unknown (and probably variable) rock type Hole support Cuttings transport & removal Drilling automation & robotics Down-force application (weight-on-bit) Bottom hole assembly cooling Bit control, localization, and telemetry Maintenance of proper temperatures/pressure for drill and for pumping water out Small hole diameter (e.g., miniaturization of sensors)

Background: Deep-hole Drilling : 

Background: Deep-hole Drilling Holes are generally either drilled or cored Holes can be lined or left unlined; liners can be continuous or segmented. Motor located on the surface or near bit. Hole diameter can be constant or reduce with depth. Holes can be straight or vary directionally Semi-autonomous directional drilling is current state-of-the art. Such drills can follow a horizontal stratum less than 1m thick. A variety of sensor measurements can be made while drilling or down-hole when drilling stops

Slide13: 

Example deep drilling System: Coiled Tubing Deployed Diamond Core Drill From The Third Dimension of Planetary Exploration -- Deep Subsurface Drilling J. Blacic, D Dreesen, & T. Mockler Los Alamos National Laboratory http://www.ees4.lanl.gov/mars/ • Micro-PDC rotary core bit • Segmented drill stem • Down hole electric motor • Overburden casing advance system with rotary reamer shoe on casing bottom • Umbilical telemetry, gas flow, cooling • Rock removed as continuous core • Cuttings moved up by auger flutes in the core drill with pulsed airflow & acoustic reciprocation to junk basket

Stated Objective and Strategy of Mars Exploration is to “Follow the Water” (MEPAG): 

Stated Objective and Strategy of Mars Exploration is to “Follow the Water” (MEPAG) Principal objective is to map the 3-D distribution and state of water in the crust at a resolution sufficient to access any desired volatile target by drilling (MEPAG, 2000). Of the planet’s estimated inventory of 500 - 1000 m of H2O, ~90-95% is thought to reside in the subsurface. Expected distribution of H2O ~0.000001% Atmosphere ~5-10% Polar Caps ~90-95% Subsurface Our ignorance about the heterogeneous nature and local thermal evolution of the crust effectively precludes theoretical of geomorphic attempts to quantitatively assess the current distribution and state of subsurface H2O. Of the various types of investigations that might be flown to address this issue, only geophysical investigations have this ability.

Slide15: 

Post-2009 “Follow the Water” Strategy: Recommended Sequence of Missions (From Clifford et al, AGU 2002) Orbital 3-D Imaging/Synthetic Aperture Radar Sounder. 20+ Station Geophysical/Meteorological Network (targeting most promising sites identified by 3-D Radar Sounder). High-Resolution Characterization and Sampling of most promising sites verified by Geophysical Network (to precisely locate where to drill). Conducted by MSL-class rover with 2-m drill, onboard analysis, and ability to cache samples for transfer to sample return vehicle. 50-100 m-Capable Drill – to access and sample high priority target identified by previous investigations. Sample return mission to collect samples obtained by rover and deep drill (vehicle could be included as part of drilling mission).

Next Steps: 

Next Steps Why think about this now? Mars Surveyor program and MEPAG are currently assessing precursor missions for human exploration of Mars. The next series of missions should focus on finding and sampling subsurface water (this is not what MEPAG currently recommends as a priority). By adopting a strategy of using liquid water as a resource, the Code T program goals merge with the Code S program goals The subsurface aquifer is also the best environment to search for life on Mars!!!