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All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Experimental dehydration of natural obsidian and estimation of DH2O at low water contents

Water diffusion experiments were carried out by dehydrating rhyolitic obsidian from Valles Caldera (New Mexico, USA) at 510-980 degrees C. The starting glass wafers contained approximately 0.114 wt% total water, lower than any glasses previously investigated for water diffusion. Weight loss due to dehydration was measured as a function of experiment duration, which permits determination of mean bulk water diffusivity, mean Dw. These diffusivities are in the range of 2.6 to 18 X 10(-14) m2/s and can be fit with the following Arrhenius equation: ln mean Dw (m2/s) = -(25.10 +/- 1.29) - (46,480 +/- 11,400) (J/mol) / RT, except for two replicate runs at 510 degrees C which give mean Dw values much lower than that defined by the above equation. When interpreted according to a model of water speciation in which molecular H2O is the diffusing species with concentration-independent diffusivity while OH units do not contribute to the transport but react to provide H2O, the data (except for the 510 degrees C data) are in agreement with extrapolation from previous results and hence extend the previous data base and provide a test of the applicability of the model to very low water contents. Mean bulk water diffusivities are about two orders of magnitude less than molecular H2O diffusivities because the fraction of molecular H2O out of total water is very small at 0.114 wt% total water and less. The 510 degrees C experimental results can be interpreted as due to slow kinetics of OH to H2O interconversion at low temperatures.

NASA Program Exobiology↗
NASA NTRS2000

A close-up look at Io from Galileo's near-infrared mapping spectrometer

Infrared spectral images of Jupiter's volcanic moon Io, acquired during the October and November 1999 and February 2000 flybys of the Galileo spacecraft, were used to study the thermal structure and sulfur dioxide distribution of active volcanoes. Loki Patera, the solar system's most powerful known volcano, exhibits large expanses of dark, cooling lava on its caldera floor. Prometheus, the site of long-lived plume activity, has two major areas of thermal emission, which support ideas of plume migration. Sulfur dioxide deposits were mapped at local scales and show a more complex relationship to surface colors than previously thought, indicating the presence of other sulfur compounds.

long duration↗
NASA NTRS1996

Hydrothermal systems on Mars: an assessment of present evidence

Hydrothermal processes have been suggested to explain a number of observations for Mars, including D/H ratios of water extracted from Martian meteorites, as a means for removing CO2 from the Martian atmosphere and sequestering it in the crust as carbonates, and as a possible origin for iron oxide-rich spectral units on the floors of some rifted basins (chasmata). There are numerous examples of Martian channels formed by discharges of subsurface water near potential magmatic heat sources, and hydrothermal processes have also been proposed as a mechanism for aquifer recharge needed to sustain long term erosion of sapping channels. The following geological settings have been identified as targets for ancient hydrothermal systems on Mars: channels located along the margins of impact crater melt sheets and on the slopes of ancient volcanoes; chaotic and fretted terranes where shallow subsurface heat sources are thought to have interacted with ground ice; and the floors of calderas and rifted basins (e.g. chasmata). On Earth, such geological environments are often a locus for hydrothermal mineralization. But we presently lack the mineralogical information needed for a definitive evaluation of hypotheses. A preferred tool for identifying minerals by remote sensing methods on Earth is high spatial resolution, hyperspectral, near-infrared spectroscopy, a technique that has been extensively developed by mineral explorationists. Future efforts to explore Mars for ancient hydrothermal systems would benefit from the application of methods developed by the mining industry to look for similar deposits on Earth. But Earth-based exploration models must be adapted to account for the large differences in the climatic and geological history of Mars. For example, it is likely that the early surface environment of Mars was cool, perhaps consistently below freezing, with the shallow portions of hydrothermal systems being dominated by magma-cryosphere interactions. Given the smaller gravitational field, declining atmospheric pressure, and widespread, permeable megaregolith on Mars, volatile outgassing and magmatic cooling would have been more effective than on Earth. Thus, hydrothermal systems are likely to have had much lower average surface temperatures than comparable geological settings on Earth. The likely predominance of basaltic crust on Mars suggests that hydrothermal fluids and associated deposits should be enriched in Fe, Mg, Si and Ca, with surficial deposits being dominated by lower temperature, mixed iron oxide and carbonate mineralogies.

Review↗
NASA NTRS2005

Physical Properties of Volcanic Deposits on Venus from Radar Polarimetry

Studies of the morphology and radar properties of volcanic deposits can aid in understanding their differences and formation. On Venus, volcanoes range in size from large highland edifices, such as Theia Mons, to small shields and domes which are often found in groups of tens to hundreds. In plains regions, windstreaks are sometimes found near shield fields, suggesting that there may be fine grained deposits associated with the volcanoes. Previous studies of Bell Regio suggest the presence of fine-grained material in a low dielectric constant triangular shaped region on the flank of Tepev Mons, which may be crater ejecta or a pyroclastic deposit spread westward by wind. The eastern caldera on Tepev Mons shows a steep trend in backscattered power with incidence angle and has high RMS-slopes, implying a finegrained covering such as ash. Radar waves can easily penetrate smooth mantling layers such as ash and aeolian deposits. If a radar system can measure two orthogonal polarizations, it is possible to detect subsurface scattering and infer the presence of surficial deposits. The Magellan spacecraft could only measure one polarization and was therefore not able to fully characterize the polarization state of the radar echoes. We compare Arecibo dual-polarization data for Venus to Magellan images and emissivity data to investigate the physical properties of volcanic deposits.

Carter, Lynn M.↗
NASA NTRS2004

Teleoperation from Mars Orbit: A proposal for Human Exploration

For a human expedition to Mars, a case can be made that the best strategy for initial exploration is not to actually land the humans on Mars, but to put the humans into Mars orbit and operate on the surface by the technology of teleoperation. This will provide the results of human exploration, but at greatly reduced risk and cost. Teleoperation of Mars surface robots from a Mars-orbital habitat will operation near real time operation with minimum time delay, giving a virtual presence on the surface. By use of teleoperation, it is possible to vastly simplify the surface exploration mission. We now have no need to develop a human-rated Mars Lander and Mars Ascent Vehicle, and we can send geologists & biologists on the mission; not VTOL pilots. It is a cheaper, simpler, and safer way to explore, and hence it will be a faster way to explore. It has the excitement of being there, at a fraction of the price. Tele-exploration from Mars orbit also allows human (virtual) presence at a wide variety of locations. With an orbital base controlling surface telerobotics, human explorers are not stuck with one base location, but can explore all over Mars. They can explore the polar caps and also near-equatorial canyon regions, from the same orbiting base. This frees the mission from landing site constraints. With no need to select a "grab bag" site that contains a large number of geologically diverse features at or near a single location; it is now possible go to all the best sites-- paleolake sites, river beds, volcanic calderas, lava tube sites, layered terrain, canyons, possible shoreline features, the North and South poles. A near-polar inclination 24-hr 39-minute period Mars orbit, for example, will put the orbital station in line-of-sight of a given region for about 8 hours per day-- one teleoperation shift. Since present day life could exist on Mars, planetary protection is also needed to preserve the (possible) fragile Mars biosphere from competition from ferocious Earth life. Isolated biospheres on Earth have been devastated when they have been exposed to alien life forms introduced-accidentally or deliberately-- from another continent. If there is life on Mars, we will wish to protect it from having to compete with introduced Earth biota. Reverse planetary protection-protecting the Earth biosphere from exposure to Mars microorganisms-is also an important consideration. Exploring from orbit will reduce biological risk by keeping humans from exposure to possible Mars microbes. A telerobotic mission will need no quarantine on return to Earth, and avoids the difficult human question of how to isolate Mars mission astronauts infected by Martian microorganisms.

Landis, Geoffrey A.↗
NASA NTRS2005

Evolution of large shield volcanoes on Venus

We studied the geologic history, topographic expression, and gravity signature of 29 large Venusian shield volcanoes with similar morphologies in Magellan synthetic aperture radar imagery. While they appear similar in imagery, 16 have a domical topographic expression and 13 have a central depression. Typical dimensions for the central depression are 150 km wide and 500 m deep. The central depressions are probably not calderas resulting from collapse of a shallow magma chamber but instead are the result of a corona-like sagging of a previously domical volcano. The depressions all have some later volcanic filling. All but one of the central depression volcanoes have been post-dated by geologic features unrelated to the volcano, while most of the domical volcanoes are at the top of the stratigraphic column. Analysis of the gravity signatures in the spatial and spectral domains shows a strong correlation between the absence of post-dating features and the presence of dynamic support by an underlying plume. We infer that the formation of the central depressions occurred as a result of cessation of dynamic support. However, there are some domical volcanoes whose geologic histories and gravity signatures also indicate that they are extinct, so sagging of the central region apparently does not always occur when dynamic support is removed. We suggest that the thickness of the elastic lithosphere may be a factor in determining whether a central depression forms when dynamic support is removed, but the gravity data are of insufficient resolution to test this hypothesis with admittance methods.

Herrick, Robert R.↗
NASA NTRS2011

Spatial Distribution of Volcanic Hotspots and Paterae on Io: Implications for Tidal Heating Models and Magmatic Pathways

Io, the innermost of Jupiter's Galilean satellites, is the most volcanically active body in the Solar. System. Io's global mean heat flow is approximately 2 W/square m, which is approximately 20 times larger than on Earth. High surface temperatures concentrate within "hotspots" and, to date, 172 Ionian hotspots have been identified by spacecraft and Earth-based telescopes. The Laplace resonance between Io, Europa, and Ganymede maintains these satellites in noncircular orbits and causes displacement of their tidal bulges as the overhead position of Jupiter changes for each moon. Gravitational interactions between Jupiter and Io dominate the orbital evolution of the Laplacian system and generate enormous heat within to as tidal energy is dissipated. If this energy were transferred out of Io at the same rate as it is generated, then the associated surface heat flux would be 2.24 +/- 0.45 W/square m. This estimate is in good agreement with observed global heat flow, but to better constrain tidal dissipation mechanisms and infer how thermal energy is transferred to Io's surface, it is critical to closely examine the spatial distribution of volcanic features. End-member tidal dissipation models either consider that heating occurs completely in the mantle, or completely in the asthenosphere. Mixed models typically favor one-third mantle and two-thirds asthenosphere heating. Recent models also consider the effects of mantle-asthenosphere boundary permeability and asthenospheric instabilities. Deep-mantle heating models predict maximum surface heat flux near the poles, whereas asthenosphere heating models predict maxima near the equator-particularly in the Sub-Jovian and Anti-Jovian hemispheres, with smaller maxima occurring at orbit tangent longitudes. Previous studies have examined the global distribution of Ionian hotspots and patera (i.e., irregular or complex craters with scalloped edges that are generally interpreted to be volcanic calderas), but in this study, we combine a new geospatial analysis technique with an improved hotspot and paterae database .

Hamilton, C. W.↗
NASA NTRS2014

Supervolcanoes Within an Ancient Volcanic Province in Arabia Terra, Mars

Several irregularly shaped craters located within Arabia Terra, Mars represent a new type of highland volcanic construct and together constitute a previously unrecognized martian igneous province. Similar to terrestrial supervolcanoes, these low-relief paterae display a range of geomorphic features related to structural collapse, effusive volcanism, and explosive eruptions. Extruded lavas contributed to the formation of enigmatic highland ridged plains in Arabia Terra. Outgassed sulfur and erupted fine-grained pyroclastics from these calderas likely fed the formation of altered, layered sedimentary rocks and fretted terrain found throughout the equatorial region. Discovery of a new type of volcanic construct in the Arabia volcanic province fundamentally changes the picture of ancient volcanism and climate evolution on Mars. Other eroded topographic basins in the ancient Martian highlands that have been dismissed as degraded impact craters should be reconsidered as possible volcanic constructs formed in an early phase of widespread, disseminated magmatism on Mars.

Mars↗
NASA NTRS2014

Sedimentology of Martian Gravels from Mardi Twilight Imaging: Techniques

Quantitative sedimentologic analysis of gravel surfaces dominated by pebble-sized clasts has been employed in an effort to untangle aspects of the provenance of surface sediments on Mars using Curiosity's MARDI nadir-viewing camera operated at twilight Images have been systematically acquired since sol 310 providing a representative sample of gravel-covered surfaces since the rover departed the Shaler region. The MARDI Twilight imaging dataset offers approximately 1 millimeter spatial resolution (slightly out of focus) for patches beneath the rover that cover just under 1 m2 in area, under illumination that makes clast size and inter-clast spacing analysis relatively straightforward using semi- automated codes developed for use with nadir images. Twilight images are utilized for these analyses in order to reduce light scattering off dust deposited on the front MARDI lens element during the terminal stages of Curiosity's entry, descent and landing. Such scattering is worse when imaging bright, directly-illuminated surfaces; twilight imaging times yield diffusely-illuminated surfaces that improve the clarity of the resulting MARDI product. Twilight images are obtained between 10-30 minutes after local sunset, governed by the timing of the end of the no-heat window for the camera. Techniques were also utilized to examine data terrestrial locations (the Kau Desert in Hawaii and near Askja Caldera in Iceland). Methods employed include log hyperbolic size distribution (LHD) analysis and Delauney Triangulation (DT) inter-clast spacing analysis. This work extends the initial results reported in Yingst et al., that covered the initial landing zone, to the Rapid-Transit Route (RTR) towards Mount Sharp.

sedimentologic↗
NASA NTRS2015

Petrology of Anomalous Eucrite QUE 94484

Most mafic achondrites are broadly "eucritic", being composed of ferroan low-Ca clinopyroxene, high-Ca plagioclase, a silica phase, ilmenite and accessory phases. Their characteristics indicate that eucrite-like basalts formed on asteroids of similar composition under similar petrologic conditions (T, P, fO2). Some eucrite-like basalts have isotopic compositions and petrologic characteristics consistent with formation on different parent asteroids (e.g., Ibitira, NWA 011). Others show small isotopic differences but no distinguishing petrological characteristics (e.g., Caldera, Pasamonte). We have begun a study of anomalous eucrite-like achondrites in an effort to seek resolution to the issues: Did the eucrite parent asteroid fail to homogenize via a magma-ocean stage, thus explaining outliers like Pasamonte? How many parent asteroids are represented by these basalts? Here we present preliminary petrologic information on anomalous basaltic eucrite QUE 94484.

Mittlefehldt, D. W.↗
NASA NTRS2016

Geologic Mapping of Ascraeus Mons, Mars

Ascraeus Mons (AM) is the northeastern most large shield volcano residing in the Tharsis province on Mars. We are funded by NASA's Mars Data Analysis Program to complete a digital geologic map based on the mapping style. Previous mapping of a limited area of these volcanoes using HRSC images (13-25 m/pixel) revealed a diverse distribution of volcanic landforms within the calderas, along the flanks, rift aprons, and surrounding plains. The general scientific objectives for which this mapping is based is to show the different lava flow morphologies across AM to better understand the evolution and geologic history.

Volcanoes↗
NASA NTRSDate not supplied

Investigating Buried Ice at Askja Volcano, Northern Iceland using Ground Penetrating Radar: A Planetary Analog Perspective

Shallow subsurface ice deposits on Mars and the Moon have been identified as potential targets for in situ resource utilization by future crewed missions to the surfaces of these bodies. On Mars, such deposits have been identified through a variety of orbital measurements at the poles, mid-latitudes, and even preserved by volcanic ash near the Tharsis Montes. At some locations, massive ice deposits have been documented to be 100 m in thickness at depths as shallow as 1 m. On the Moon, the presence of thick, massive ice has not been confirmed; however, orbital observations indicate that the upper 1-2 m of regolith may contain a few weight percent in thermally favorable locations. Eruptions of the Askja Volcano in March, 1875 and November, 1961 deposited abundant pyroclasts, which blanketed and insulated fresh snowfall that later densified into massive ice and is preserved today. The pyroclasts consist of a buff colored pumice from the eruption in 1875 and basaltic lapilli and ash from the eruption in 1961. The largely unvegetated, unconsolidated nature of the pyroclasts and their stratigraphic relationships with shallow subsurface ice make them potentially analogous to some ice deposits within regolith and pyroclasts at the Moon and Mars. Ground penetrating radar(GPR) can be used by future human or robotic missions to identify water ice similarly preserved in the shallow subsurface of these bodies. Our team conducted over 66 GPR surveys inside and surrounding the Askja caldera in August 2019 at 200 and 400 MHz to map both the volcanic deposits and the subsurface ice deposits. We also used a hammer drill augur to take boreholes in order to confirm subsurface stratigraphy and the presence of ice down to 1-1.5 m and aerial surveys using a Mavic 2 Pro quadcopter at each site for additional context. We observed shallow ice deposits within pore spaces of the pyroclasts at depths of ~15-30 cm and pure ice deposits at varying depths (0.6-1 m) as thick as 2-3 m. We also plan to use the data to characterize the frequency-dependent attenuation of the radar signal as it travels through volcanoclastic material and ice in the subsurface. Our investigation of Askja as a planetary analog will provide insight into analytical methods that can be used to investigate subsurface water ice from surface operations at other terrestrial bodies.

Geophysics↗
NASA NTRSDate not supplied

The Stop-and-Go Mechanism: Towards an Integrated Approach to Model Seismicity, Outgassing, Deformation, and Thermal Unrest at Active Volcanoes

Connecting the geophysical and geochemical signals recorded at and above the surface of volcanoes with source mechanisms is fundamental to understand transitions from quiescence to eruption, and to integrate the behavior of volcanoes with their regional seismotectonic and hydrological context. Some of these signals include shallow volcanic tremor, a long-lasting (minutes-to-years) ground vibration detected in volcanic areas during unrest; volcanic outgassing, which shows intriguing periodicities over multiple scales, as revealed by space-borne instruments and by ground-based, high-frequency (~1 Hz), sampling methods; inflation and deflation of volcanic edifices, commonly associated with subsurface volume changes; and large-scale (from a few to tens of km2), low-temperature, thermal anomalies, a newly-discovered signal that has been observed to emerge on volcanic flanks from months-to-years prior to gas- and magma-driven eruptions. Traditionally, these geophysical and geochemical signals have been modelled independently, which limits our interpretation of subsurface processes and thus our assessment of unrest. In this work, we show through lumped-parameter models, numerical simulations, and preliminary laboratory experiments that many of the signals recorded around volcanoes can be integrated into a common “stop-and-go” mechanism. In particular, we found that they can arise spontaneously when taking into account the feedbacks between the temporary accumulation of gas and/or magma in the crust (“stop”), and the diffusive transfer of gas and heat towards the surface (“go”). For example, we find that the “stop-and-go” mechanism can explain: (i) the emergence of monochromatic, broadband, and harmonic tremor; (ii) the periodic components commonly observed in volcanic outgassing time series; (iii) the link between large-scale thermal anomalies and shallow hydrothermal systems; (iv) the reported time lags between large-scale thermal anomalies and deformation; and (v) the breathing of potentially destructive volcanic calderas. The “stop-and-go” mechanism provides a consistent and realistic framework to link multiple geophysical and geochemical signals with the processes leading to volcanic unrest and eruption.

volcanoes↗
NASA NTRSDate not supplied

Are the Surface Textures of Pluto’s Wright Mons and its Surroundings Exogenic?

The Wright Mons region of Pluto remains one of the most intriguing and enigmatic landscapes on the planet. Wright Mons is a large mountain ~150 km across that rises ~4 km above its surroundings, sports a central depression that is ~45 km across and ~4 km deep, and was tentatively assigned a cryovolcanic origin immediately following the New Horizons encounter in 2015 (Fig. 1) [1,2,3]. But the absence of obvious lateral flow features and the lack of unambiguously diagnostic characteristics of calderas or vents within the central depression have challenged the development of specific formation hypotheses. The pervasive cover of pillow-like hummocks, typically 7-20 km across, on the flanks and surroundings of Wright Mons have naturally figured into various working explanations for the formation of this region (Fig. 2). Individual hummocks themselves are covered by a km-scale blocky (or coalescing short ridge) texture. The similarity in size and shape of the convex hummocks and the style of their organization, such as forming avaguely concentric fabric near the summit, potentially lend themselves to an endogenic origin.

Jeffrey M Moore↗
NASA NTRSDate not supplied

TRIDENT Drill Validation at Mars and Lunar Analog Field Sites

Drilling on Earth is typically a human-intensive activity. Drilling on other planets is further complicated by the lack of prior local field surveys of their target area, hence blindly drilling into uncertain target rocks. Field conditions on the Moon or Mars are also different than for shallow drilling on Earth: lower temperatures and pressures, less power available, low masses (hence less weight-on-bit). Given the cost of transport from Earth, no drilling muds or working fluids are likely to be available to carry away cuttings. And impact-gardened regolith and dust vary mechanically and texturally from most terrestrial soils. The Regolith and Ice Drill for Exploration of New Terrains (TRIDENT) is a rotary-percussive 1m-class drill from Honeybee Robotics. It is low-power (rotary and percussive actuators are 200 W each) and lightweight (<20 kg) with the maximum weight on bit limited to 200 N. TRIDENT has been manifested for the Volatiles Investigating Polar Exploration Rover (VIPER) and PRIME-1 lunar south pole missions in 2024, has previously been field tested at a hot, dry analog site in the Atacama Desert, and in lunar conditions in thermal vacuum chamber tests. TRIDENT was also part of the 2019 Icebreaker Mars Discovery proposal, as well as in the Mars Life Explorer concept. During ARADS tests, drill control and fault recovery automation software enabled hands-off operations of a rover-mounted TRIDENT drill. TRIDENT Drill Analog Site Validation: Past TRIDENT tests in thermal vacuum (TVAC) chambers targeted containers of manufactured lunar simulants with added volatiles. 2022 TRIDENT ambient testing at NASA Ames drilled into cemented lunar simulant materials. Low cuttings-permeability led to cuttings buildup, and drill choking and binding was observed. The Atacama analog site in ARADS had desiccated unconsolidated sediments that did not challenge the TRIDENT design. However, lunar polar regolith is expected to be diverse and heterogeneous with varying clast sizes, with abundant impactites and perhaps subsurface ice deposits. Neither the simulants nor Atacama testing had completely covered the TRIDENT-targeted field characteristics, motivating further analog tests prior to the planned lunar missions. To gain more insight into the behavior of the TRIDENT hardware in diverse impactites and subsurface ice, and to verify the software automation in that environment, in August 2023 TRIDENT was brought to Haughton Crater, a field analog site in the Canadian Arctic. In September 2023 the same drill was brought to the Bishop Tuff in southern California to verify whether drilling binding behaviors previously seen in lunar simulant testing would be observed in naturally occurring fine-grained massive layers. The ~22 Ma Haughton Crater impact structure is located at 75 ̊22’ N, 89 ̊41’ W, on northwestern Devon Island, Nunavut, Canada. Numerous deposits of pale-grey crater-fill polymictic impact-melt breccia are found within the crater with a typical thickness reaching ~125 m or greater and covering ~60 km -2 . An approximately 600m-thick permafrost layer is also present with ice typically found within 0.5-0.6m of the surface. The volcanic tableland north of Bishop, CA exposes densely welded tuff laid down during the eruption that created the Long Valley Caldera at approximately 0.76 Ma. Extensional faults and the Owens River gorge expose cross-sections across the plateau. The area is viewed as an analog site for Mars features believed to be of pyroclastic origin. Results: Haughton Crater.Drilling tests were conducted 8-13 August 2023 at a previously undisturbed area separated 5-10 m from past years’ Drill Hill test sites (75.4208, -089.7613). In six days, TRIDENT drilled 8 holes to nearly 1 m depth each, totaling 7.80 m. The active layer/ice boundary was at ~67 cm depth, with a total of approximately 2.4 m drilled into ice or ice-cemented impact breccia. During drilling, five drill fault states were observed and successfully recovered. Holes 23-1, 4 and 7 were drilled under manual control, using Honeybee’s Thorax user interface. Holes 23-5, 6, and 8 were drilled with the Ames IBexec automated drilling control software. TRIDENT was observed to have little difficulty in the thawed uncemented impact breccia above the active layer boundary, but required percussion to make slower headway in the ice-cemented breccia. In Hole 23-7 (Fig.1), drilling slowed down in a massive unit just above the active-layer boundary (perhaps a large rock extending into the ice-cementation?), with only 7cm progress made in 27 minutes of high auger torque and constant percussion, leading to a choking fault and then a binding fault. A similar pattern had been observed in TRIDENT Rio Tinto test data from 2017 [6] as well as in the 2022laboratory tests.Bishop Tuff.A team from NASA Ames and the US Geological Survey deployed the same TRIDENT drill to Bishop Sites 1B and 1C (37.4203, -118.4289; 37.4265, -118.4215) on 13-16 September 2023, on the Bishop Tuff plateau. A third drill site was used 17-18 September 2023(37.4598, -118.3667) in an abandoned pumice mine. Four holes (totaling 2.5m depth) were drilled into the fine-grained, meters-thick tuff units at Sites 1B and 1C, and a further two boreholes (totaling 1.98m depth) were made at the pumice site. Drill behavior in the tuff below 10 cm depth was similar to that seen at 65-74 cm depth in Haughton Hole 23-7 (Fig. 1) and that seen in the 2022 lab simulant drilling. Drill safety torque limits were exceeded multiple times resulting in drill stops downhole. These freezes then required external added torques (with a pipe wrench) to resume rotation, to unstick the drill for withdrawal. To prevent this choking and binding behavior we found that more-frequent cuttings removal was necessary, e.g., reducing the “drill bite” size from the nominal 10 cm to 2 cm per bite --bringing the auger up to the surface more frequently, as seen in Bishop Site 1C Hole 2 (Fig.2). This permitted slow progress without drill binding and without external interventions. Conversely, TRIDENT drilling in the more porous pumice target material showed no cuttings buildup issue, and single bites as large as 40 cm were demonstrated. Discussion: We observed that TRIDENT easily penetrated unconsolidated heterogeneous soils (both above the active layer boundary at Haughton and previously in the Atacama). Cemented or consolidated targets that were cuttings-permeable (icy impact breccia, pumice) required more energy applied and percussion. However, in non-cuttings-permeable targets (welded microporous tuff, cemented simulants, boulder) TRIDENT was observed to be prone to excessive cuttings accumulation leading to choking/binding faults and stalling. The wedge cutting bit, used by TRIDENT in field tests and in its flight versions, pulverizes the target rock and creates fine cuttings that ideally are transported up the auger spirals for removal. In porous, fractured or vesicular target materials (such as at the Bishop pumice site) a significant portion of the cuttings are pushed aside, but for non-fractured, microporous targets the cuttings remain in the borehole and accumulate. Rock powder is relatively incompressible as a working fluid at only 100-200N downward force (TRIDENT limits) and hence eventual drilling progress slows or stops. Our recommended strategy for improving TRIDENT cuttings removal in massive target units with low cuttings-permeability is to reduce TRIDENT bite sizes when encountering these units, from 10cm to as little as 1-2cm, to effectively bail the accumulating cuttings. This approach was demonstrated to reduce choking and allowed slow progress to continue in cuttings-impermeable microporous target units (viz. the Bishop tuff in our September 2023 tests or cemented simulants in 2022 ambient tests).

robotic drilling↗
DOE OSTI2017

Improved image of intrusive bodies at Newberry Volcano, Oregon, based on 3D gravity modelling

Beneath Newberry Volcano is one of the largest geothermal heat reservoirs in the western United States and it has been extensively studied for the last 40 years. Several magmatic intrusions have been recognized at depths between 2.5 and 8 km and some of them identified as suitable targets for enhanced geothermal energy and tested during two previous EGS campaigns. These subsurface structures have been intersected by three deep wells and imaged by various geophysical methods including seismic tomography and magnetotellurics. Although three high quality gravity surveys were completed between 2006 and 2010 as part of various projects, a complete synthesis and interpretation of the gravity data has not yet been performed. Regional gravity data also exist in the vicinity of the Newberry volcano and have been added to these surveys to constitute a dataset with a total of 1418 gravity measurements. When coupled with existing geologic and geophysical data and models, this new gravity dataset provides important constraints on the depth and contours of the magmatic bodies previously identified by other methods and thus greatly contributing to facilitate any future drilling and stimulation works. Using the initial structures discovered by seismic tomography, inversion of gravity data has been performed. Shape, density values and depths of various bodies were allowed to vary and three main bodies have been identified. Densities of the middle and lower intrusive bodies (~2.6-2.7 g/cm3) are consistent with rhyolite, basalt or granites. Modeled density of the near-surface caldera body match that of a low density tephra material and the density of the shallow ring structures contained in the upper kilometer correspond to that of welded tuff or low-density rhyolites. Modeled bodies are in reality a composite of thin layers; however, average densities of the modeled gravity bodies are in good agreement with the density log obtained in one well located on the western flank (well 55-29). Final gravity data residuals show that most of the observed gravity anomalies at the surface can be explained by the modeled gravity bodies and are consistent with other site characterization information.

Cascade Range↗
DOE OSTI2015

Regional and Local Geothermal Potential Evaluation: Examples from the Great Basin, USA, Iceland and East Africa

In both tectonically and magmatically mediated geothermal systems, geologic structures play a crucial role in focusing geothermal fluid circulation in the upper crust. In a variety of geothermal provinces worldwide, normal and strike-slip faults, caldera related faults, as well as fractures and fissures related to dikes and other magmatic intrusions generate the fracture permeability utilized for geothermal circulation. Localities where the above structures intersect and interact are characterized by the most robust generation and maintenance of fracture permeability, and therefore are the most favorable conduits for geothermal circulation. We present an evaluation of the structural geometries that tend to generate high density faulting and fracturing and an evaluation of the orientations of those structures with respect to the ambient stress conditions in three regions of high geothermal potential; The Great Basin, USA, Iceland, and east Africa. These analyses provide first-order constraints on areas that have favorable conditions for permeability and where future exploration for geothermal resources could be focused. In the Great Basin, USA, fault step-overs, fault terminations and accommodation zones are among the most common structural settings of known geothermal activity. Analysis of the geometry of these structures with respect to the ambient stress conditions reveals locations where faults associated with these structures are favorably oriented for enhanced fracture permeability. In magmatically active extensional provinces, like Iceland and east Africa, heat associated with shallow magmatic intrusions beneath volcanic centers drives geothermal circulation in near-surface fracture permeability conduits. Accentuated fault and fracture density and fracture permeability is generated by both axially oriented faults and fractures associated with axial rift zones and radially oriented structures near volcanic centers. Although heat from magmatic intrusion is most robust at volcanic centers, a high density of young intrusions may actually result in decreased permeability through closing of fracture networks. The locations of these three types of features; axial faults and fractures, radial structures, and young magmatic intrusions, all play a critical role in determining the most favorable locations for fracture permeability and fluid flow in magmatic geothermal systems. Within and around the margins of volcanic centers, where radial structures associated with volcanic centers interact and intersect with axially oriented structures associated with axial extension are the most favorable locations for fracture permeability and geothermal fluid circulation in magmatic extensional geothermal systems.

15 GEOTHERMAL ENERGY↗