Keith Harrison

Southwest Research Institute · Space Studies

Tropical ground ice on Mars undergoes long-term sublimation and likely exospheric escape. Without restriction of sublimation, the cryosphere would eventually breach, leading to massive loss of any underlying groundwater. We seek to understand the conditions under which the ground-ice seal, groundwater, and subsurface habitability are preserved. Usi...

Southern mid-latitude (SML) recurring slope lineae (RSL) are narrow (0.5–5 m) dark albedo features that emanate from bedrock and incrementally lengthen down steep slopes that preferentially face the equator. We observe that SML RSL begin lengthening prior to southern summer at a solar longitude (Ls) of 245° ± 11° when Mars Global Surveyor Thermal E...

Flowing water, possibly brine, has been suggested to cause seasonally reappearing, incrementally growing, dark streaks on steep, warm slopes on Mars. We modeled these Recurring Slope Lineae (RSL) as isothermal water flows in thin surficial layers driven by gravity and capillary suction, with input from sources in the headwall and loss to evaporatio...

RSL lengthen for ~97 ± 31 sols when surface afternoon temperatures are >273 K. This suggests high concentrations of brine are not necessary to generate RSL.

Electromagnetic (EM) investigation depths are larger on Venus than Earth due to the dearth of water in rocks, in spite of higher temperatures. Whistlers detected by Venus Express proved that lightning is present, so the Schumann resonances ∼10–40Hz may provide a global source of electromagnetic energy that penetrates ∼10–100km. Electrical conductiv...

Understand Venus geodynamics from 180,000 ft.

The Valles Marineris canyons are among the deepest of topographic depressions on Mars. As such, they may be expected to have served as sinks for a variety of mobile materials, including water, regardless of their particular formation history. The interpretation of ILD formation is not critical to the putative Valles Marineris lake considered here....

Reconstructions of the early thermal history of the H-chondrite parent body have focused on two competing hypotheses. The first posits an undisturbed thermal evolution in which the degree of metamorphism increases with depth, yielding an “onion-shell” structure. The second posits an early fragmentation–reassembly event that interrupted this orderly...

The nature of strong martian crustal field sources is investigated by mapping and modeling of Mars Global Surveyor magnetometer data near Apollinaris Patera, a previously proposed volcanic source, supplemented by large-scale correlative studies. Regional mapping yields evidence for positive correlations of orbital anomalies with both Apollinaris Pa...

We present a broad survey of available H-chondrite age and cooling rate data which, together with thermal and dynamical simulations, constrain the early history of the parent body.

A broad spatial correlation between strong martian crustal magnetic fields and the valley networks, which are indicative of surface water erosion, has previously been reported. In this paper, we report initial evidence for a correlation of phyllosilicate exposures identified to date using Mars Express OMEGA data with strong crustal fields and valle...

Groundwater flow on Mars likely contributed to the formation of several types of morphologic and mineralogic features, including chaotic terrains, valley networks, Meridiani Planum geologic units and, potentially, sulfate and phyllosilicate deposits. A central issue for these features is the spatial scale of groundwater flow required for their form...

The only ice-free rocky units that SHARAD has been successful at penetrating into are in Elysium and Amazonis Planitia. These are the youngest units on Mars and probably have low radar loss because they have been insufficiently exposed to water.

Martian chaotic terrains have traditionally been regarded as groundwater source regions for outflow channels. However, the near ubiquitous presence of upstream fluvial inlets suggests that their status as source regions should be revisited.

We report correlations of (a) phyllosilicate exposures identified using Mars Express OMEGA data with strong crustal fields and valley networks; and (b) weaker magnetic anomalies with the Medusae Fossae Formation adjacent to Apollinaris Patera.

The Valles Marineris canyon system of Mars is closely related to large flood channels, some of which emerge full born from chaotic terrain in canyon floors. Coprates Chasma, one of the largest Valles Marineris canyons, is connected at its west end to Melas Chasma and on its east end to chaotic terrain-filled Capri and Eos Chasmata. The area from ce...

We investigate cryosphere disruption by superlithostatic groundwater pressures on Mars. Global groundwater models with various aquifer recharge sources, topographic assumptions, disruption criteria, and permeability distributions are considered.

The large outflow channels of Chryse Planitia, Mars, are thought to have been carved by floodwaters discharged from an aquifer beneath a confining cryosphere. However, conventional models of groundwater flow require optimistically high permeabilities to produce, in a single flooding event, the discharge rates and volumes inferred from channel morph...

Maps of the vector components of the martian crustal magnetic field over the strongly magnetized Terra Cimmeria/Sirenum region are constructed using Mars Global Surveyor magnetometer data. Although pronounced east–west trending anomalies are present on the radial and north field component maps at the mapping altitude (∼360–380 km), these trends are...

Martian outflow channels were likely formed by multiple erosive flooding events. We investigate the number and duration of events required, and the implications for possible delivery mechanisms.

1] Fluvial erosion on early Mars was dominated by valley networks created through a combination of groundwater processes and surface runoff. A reduced greenhouse effect due to CO 2 loss, together with a declining geothermal heat flux, promoted the growth of a cryosphere and a Hesperian hydrologic regime dominated by outflow channel formation. We te...

Maps of the vector components of the Mars crustal magnetic field are constructed at the mapping altitude (360 to 410 km) using a selected set of data obtained with the Mars Global Surveyor magnetometer during 2780 orbits of the planet in 1999. Forward modeling calculations are then applied to six relatively strong and isolated, dominantly dipolar,...

The morphological differences between densely dissecting, degraded martian valley networks and sparsely dissecting, pristine networks, are proposed to result from a temporal evolution away from surface runoff erosion toward groundwater processes.

Improved simulations of martian groundwater flow demonstrate the effects of Tharsis recharge on circum-Chryse outflow channel discharge for different initial conditions and aquifer properties, and are supported by observational evidence.

The large Martian outflow channels terminating in Chryse Planitia are remnants of Hesperian flooding events involving the localized discharge of millions of cubic kilometers of subsurface water. Given reasonable crustal porosities, such volumes cannot be stored in the regional aquifer and recharge is required. Initial results of dynamic groundwater...

The large martian outflow channels terminating in Chryse Planitia are remnants of flooding events involving the localized discharge of millions of cubic kilometers of subsurface water, more than can be regionally stored in the crust. We use a dynamic groundwater model to demonstrate that snowpack or glaciers on the Tharsis rise, formed during perio...

We use a dynamic finite-difference model to simulate martian landslides in the Valles Marineris canyon system and Olympus Mons aureole using three different modal rheologies: frictional, Bingham, and power law. The frictional and Bingham modes are applied individually. Fluidized rheology is treated as a combination of frictional and power-law modes...

The global flow of groundwater on Mars is modeled numerically under a range of conditions prevailing at different stages in Mars' history. Special attention is given to the global connectivity of the flow.

Models of hydrothermal groundwater circulation can quantify limits to the role of hydrothermal activity in Martian crustal processes. We present here the results of numerical simulations of convection in a porous medium due to the presence of a hot intruded magma chamber. The parameter space includes magma chamber depth, volume, aspect ratio, and h...