ATHABASCA VALLES:

FOLLOWING THE WATER

JIM RICE

and

TIM PARKER

Contributors: A. McEwen, D. Burr,

S. Sakimoto, and A. Haldemann

SCIENTIFIC OBJECTIVES

DRIVING SITE SELECTION

The landing sites will be selected so that they show two different types of evidence for the action of liquid water, such as mineralogic or geomorphologic (outflow sediments or hydrothermal deposits) and where hypotheses related to aqueous activity can be further tested using the rovers and their payloads.

The target composition data combined with the context and landing site information are intended to support the testing of hypotheses regarding the geologic history and the nature of past aqueous processes.

Scientific Rationale for

Athabasca Valles Sites

Follows the Water:

Diversity of Geologic Processes

Fluvial: channels, streamlined islands, scour

Hydrothermal: fissure vents for water/ lava

Lacustrine: fine scale layered material

Ground Ice: rootless cones, patterned ground

Volcanic: lava flows, fissure vents for lavas

Elysium Regional Geology Overview

VOLCANIC

Elysium Volcanic Province: 2^nd largest volcanic region on Mars (Elysium Mons, Albor Tholus, Hecates Tholus, Cerberus Rupes).

Geomorphology: volcanic edifices, fissure vents, lava plains, flow fronts

Eruption style: low viscosity flood volcanism followed by central construct building then back to flood eruptions.

Timing: Young or older? Crater counts suggest very young ages (~10 ma) but it appears that in many regions this surface is being exhumed.

Implications: on thermal history of Mars, indicates that sufficient heat in upper mantle generated large quantities of lava with high eruption rates possibly very late in history (geothermally still active??). Water and heat: Exobiology?

Elysium Regional Geology Overview

FLUVIAL

Outflow Channel Complex: Extensive network of channels associated with volcanoes and fissures (Athabasca, Marte, Granicus, Iberus, Ituxi, and Patapsco Valles).

Geomorphology: channels, streamlined islands, scour, collapsed terrain (Water); rootless cones, patterned ground (Ice). Note: Rice and Parker suggest that the “platy flows” may be flood deposits (jökulhlaups) and not lava flows. These sediments “froze up” forming a debris mantled ice rich deposit. The analogy is polar pack ice with pressure ridges. Alternatively, this ice choked flood deposit would undergo sublimation leaving behind ice casts and crevasse fills.

Flood Sources: volcano-ground ice interactions, fissures, eroded or buried outflow channel.

Timing: Young or ancient? Crater counts suggest very young ages (~10 ma) but it appears that in many regions this surface is being exhumed.

Implications: near surface ice lenses/ice rich permafrost or deep seated aquifers were preserved for extended periods of time in equatorial regions and that specific local geologic conditions caused the release of water (hydrothermal) to the surface in recent times or that an ancient buried or eroded outflow channel flowed across this region. Exobiology?

Elysium Regional Geology Overview

LACUSTRINE

Observation: Extensive region of fine scale layered, friable, stripped material. This unit is currently being stripped off the underlying rougher plains unit (volcanic or flood deposit?).

Ground Ice

Observation: rootless cones, patterned ground.

ATHABASCA VALLES:

WHAT ATHENA CAN do

Instrument(s): Pancam, MI, RAT

1. Observe morphology and stratigraphy of large and small scale landforms

2. Spatial distribution of rocks and soils

3. Textures and structures of rocks and soils

Results:

1. The above observations and measurements will aid in determining if MER is on fluvial, lacustrine, hydrothermal, or volcanic terrain based on morphology, grain size, shape, sorting, cements and sedimentary structures such as bedding, imbrication, ripple marks, and veins, and distribution and texture of rocks and soils.

2. Extract clues from the geologic investigation, related to the environmental conditions when liquid water was present and assess whether those environments were conducive for life.

3. Calibrate and validate orbital remote sensing data and assess the amount and scale of heterogeneity at each landing site and put them in geologic context.

ATHABASCA VALLES:

WHAT ATHENA CAN do

Instrument(s): Mini-TES, APXS, Mössbauer, Pancam, RAT

1. Mineral identification and abundance determination (carbonates,clays,oxides,silicates)

2. Iron-bearing mineralogy of rocks and soils and iron oxidation state

3. Detailed analyses of selected rocks and soils to determine their elemental composition

Results:

1. Determine rock and soil mineralogy, specifically identify water-bearing minerals and minerals deposited by precipitation, evaporation, sedimentary cementation, or hydrothermal activity.

2. Extract clues from the geologic investigation, related to the environmental conditions when liquid water was present and assess whether those environments were conducive for life.

3. Calibrate and validate orbital remote sensing data and assess the amount and scale of heterogeneity at each landing site and put them in geologic context.