1. Investigation: Map the 3-dimensional distribution of water in all its forms. Zones of liquid water in the subsurface provide the most likely environments for extant life on Mars. In the absence of life, such environments could also sustain pre-biotic chemistry of interest for understanding the origin of life on Earth. Requires global remote sensing of water in all its forms to identify the locations, phases, and, if possible, temporal changes in near-surface water budgets.

2. Investigation: Carry out in situ exploration of any areas suspected of harboring liquid water in the subsurface. These studies will be used to validate remote sensing observations from orbit and to explore for life or prebiotic chemistry. Requires subsurface drilling (depths of meters to km’s), in situ instrumentation to detect water in all its forms and to analyze rocks, soils and ices for organic compounds or to detect life.

4. Investigation: Determine the array of potential energy sources available on Mars to sustain biological processes. Biological systems require energy which can come from a variety of sources, including chemical, geothermal and incident radiation (sunlight). Requires 1) orbital remote sensing to map the mineralogy and geochemistry of Martian surface deposits, to detect localized geothermal "hot-spots" in the shallow crust, and to locate point sources of reduced volatiles (e.g. gas-emitting vents, or "fumeroles") and 2) the in situ characterization of surface mineralogy, elemental chemistry (including volatiles and organic compounds) of soils, rocks and ices at the most favorable sites (i.e. those that had prolonged hydrological activity) and sample returns for more detailed characterization in Earth labs.

5. Investigation: Determine the nature and inventory of organic carbon in soils and ices of the Martian crust. Carbon is a fundamental building block for life. It may exist within soils and ices of the Martian crust in a variety of heretofore undetected biotic and abiotic forms. Its distribution would exert a primary control on where and how life could develop. Requires in situ exploration of surface and subsurface soils and ices using instrumentation that can detect a wide range of carbon compounds and sample returns for more detailed characterization.

6. Investigation: Determine the distribution of oxidants. Results from Viking suggest that unknown oxidation processes in modern soils on Mars are responsible for the selective destruction of organic compounds. The distribution of oxidants in the Martian crust is likely to have been a controlling factor in determining where, when and how life may have developed. Requires instrumentation for determining the geochemistry and mineralogy of surface and subsurface samples.

1. Investigation: Determine the locations of sedimentary deposits formed by ancient surface and subsurface hydrological processes. Such deposits provide the best repositories for preserving a fossil record of ancient Martian life. Requires global mapping of surface geomorphology and mineralogy, followed by the in situ characterization of surface mineralogy and geochemistry in order to provide "ground truth" for orbital observations and to assist in the selection of the best sites and samples for return to Earth.

2. Investigation: Search for Martian fossils (morphological and chemical biosignatures of ancient life). Life leaves behind a variety of fossil bio-signatures in water-deposited sedimentary rocks, providing a record of its former presence. Based on studies of the fossil record on Earth, we know that only certain environments and types of deposits provide favorable settings for the long-term preservation of fossil biosignatures. These include environments where fine-grained, clay-rich deposits are laid down in lakes and streams, or where minerals precipitate rapidly from water in the presence of organisms. Locating the most favorable deposits for preserving fossil biosignatures requires orbital mapping of geomorphology and mineralogy, complemented by in situ microscopic imaging, mineralogy, organic and inorganic chemistry (inclusive of isotopic and trace element) and targeted sample returns.

3. Investigation: Determine the timing and duration of hydrologic activity. To assess the potential for the origin and evolution of life on Mars during the planet's history, we need to know when, where, and for how long liquid water environments were present at the surface and in the subsurface. This is a historical question that requires the development of stratigraphic (age) frameworks for deposits based on orbital mapping and surface in situ measurements, followed by sample returns from key sites and radiometric age dating of rock and mineral samples in Earth-based labs.

1. Investigation: Search for complex organic molecules in rocks and soils of the Martian crust. The steps in pre-biotic chemistry that lead to the first living organisms on Earth are presently unknown. On the Earth the record of those early events has been largely destroyed by plate tectonics and weathering. If life arose on Mars, it would have probably consumed and transformed much of the original organic inventory present. However, if life subsequently died out in surface/near surface environments, then new pre-biotic chemical processes would be expected to arise. The record of pre-biotic chemistry in an Earth-like setting on early Mars is considered fundamentally important in developing our understanding of the basic chemical steps that preceded the appearance of life on Earth. Because Mars lacks plate tectonics and a pervasive weathering cycle, it may provide an unrivaled record of early pre-biotic chemical events in an Earth-like setting. The exploration for pre-biotic chemistry ultimately requires a different approach than the search for the extant biochemistry. Thus, it is important to distinguish between the two activities. The search for pre-biotic chemistry will require studies of both modern aqueous environments (e.g. groundwater, ice-brine transitions, hydrothermal systems, etc.), as well as the record of aqueous paleoenvironments preserved in ancient sedimentary rocks. Targets for in situ studies must be first identified from orbit based on geomorphology and mineralogy (see I.B.1) and then mobile platforms (rovers) used to determine mineralogy, geochemistry, and organic chemistry and to select samples for detailed analysis in Earth-based labs.

2. Investigation: Determine the changes in crustal and atmospheric inventories of organic carbon through time. Changes in the atmospheric and crustal carbon inventories over geologic time would have greatly affected the pre-biotic chemistry and climate of the Martian surface, and hence, the potential for life to develop. This objective parallels investigation I.A.4. (determine the crustal inventory of carbon) but seeks to integrate that information over time. Thus, this objective is posed in a historical way that requires a stratigraphic (temporal) framework for sampling (established through detailed geological mapping from orbit) and the return of samples to Earth for detailed organic chemical analysis and radiometric age-dating.

1. Investigation: Determine the processes controlling the present distributions of water, carbon dioxide and dust. Understanding the factors that control the present annual variations of volatiles and dust on Mars is a necessary first step to determining to what extent today’s processes have controlled climate change in the past. Requires, in priority order: 1) global mapping of the time-varying three-dimensional distributions of dust, water vapor, carbon dioxide, thermal state, and radiative forcing of the atmosphere, surface and near-subsurface over at least one annual cycle; 2) landed observations of the exchange of volatiles and dust between the surface and atmosphere on daily and seasonal time scales.

2. Investigation: Determine the present-day stable isotopic and noble gas composition of the present-day bulk atmosphere. These provide quantitative constraints on the evolution of atmospheric composition and on the source and sinks of the major gas inventories. Requires, in priority order: 1) Single in situ, high-precision measurement of atmospheric isotopic composition; and 2) return of pristine atmospheric samples for detailed analysis, including age dating.

3. Investigation: Determine long-term trends in the present climate. Seasonal variations and annual budgets of volatiles and dust are known to vary from year-to-year. Determining long-term trends will test to what degree the Martian climate is changing today. Requires: 1) Extension of the measurements of (A1) to multiple Mars years, and 2) long-term monitoring of key atmospheric variables (e.g., pressure, temperature, dust opacity, water) at globally representative sites (network science).

4. Investigation: Determine the rates of escape of key species from the Martian atmosphere, and their correlation with solar variability and lower atmosphere phenomenon (e.g. dust storms). Requires: Global orbiter observations of species (particularly H, O, CO, CO₂ and key isotopes) in the upper atmosphere, and monitoring their variability over multiple Martian years.

5. Investigation: Search for micro-climates on Mars of special interest. Detection of exceptionally or recently wet or warm locales and/or areas of significant change in surface accumulations of volatiles or dust would identify prime locations for detailed in situ exploration. Requires global search for anomalous locales, as compared to typical planetary values, or changes in, volatile distributions and surface properties (e.g., temperature or albedo).

1. Investigation: Find physical and chemical records of past climates. These provide the basis for understanding the extent and timing (e.g., long-term gradual change or abrupt transition) of past climate change on Mars. Requires: 1) targeted remote sensing of stratigraphy at higher spatial resolution than currently planned (goal: 15 cm/pixel for stratigraphy) and of the presence of acqueous weathering products (goal: regional at 100m; targeted locales at < 100 m); 2) landed exploration of known layered deposits and outcrops to determine chemical and isotopic composition; and 3) returned samples from selected sites to determine age history and precise chemical and isotopic composition of weathering products and trapped gassed in ice and rocks.

2. Investigation: Characterize history of stratigraphic records of climate change at the polar layered deposits, the residual ice caps, and elsewhere on the planet. The polar regions have surface morphologies indicating repeated climate change, possibly in the geologically recent past. A key to understanding their histories is good relative dating of polar layering and volatile reservoirs. Requires: 1) In situ observation of surface and near-surface morphology and composition; and 2) Returned samples of layered materials for detailed analysis, including age dating.

3. Investigation: Characterize the contributions of volcanic activity and meteoritic bombardment to enhancement or erosion of atmospheric volatiles and the emplacement of layered material over time. The keys are the quantity of materials involved and the rates of their emplacement or removal. Requires: 1) In situ and remote sensing of the composition of volcanic and igneous rocks/deposits; and 2) Returned samples of materials to determine their gas content and ages.

A. Objective: Determine the nature and sequence of the various geologic processes (volcanism, impact, sedimentation, alteration etc.) that have resulted in formation of the Martian crust and surface (investigations in priority order)

1. Investigation: Determine the present state, distribution and cycling of water on Mars. Water is the critical limiting resource for the development and sustenance of life and for future human exploration. Requires global observations using geophysical sounding (radio or radar), gamma ray spectroscopy, image interpretation and geologic mapping, observations and geophysical sounding from landers, drilling.

2. Investigation: Evaluate sedimentary processes and their evolution through time, up to and including the present. Fluvial and lacustrine sediments are among the most likely sites to detect traces of past or present life and sediments record the history of water processes on Mars. Eolian sediments record a combination of globally-averaged and locally-derived fine-grained sediments and weathering products. Sediments are also likely past or present aquifers. Requires knowledge of the age, sequencing and composition of sedimentary rocks (including chemical deposits), as well as the rates, durations, and mechanics of weathering, cementation, and transport processes. Techniques include global imaging and spectroscopy, topography, returned samples, in-situ chemical and mineralogical analyses, geologic mapping, geochronology, drilling.

3. Investigation: Calibrate the cratering record and the absolute age scale for Mars. The evolution of the surface, interior, and surface environments of Mars, as well as possible evolution of life, must be placed in an absolute timescale, which is presently lacking for Mars. Requires absolute ages on at least one returned rock (not soil) sample from a well-characterized terrain of intermediate age.

4. Investigation: Evaluate igneous processes and their evolution through time, including the present. This study includes volcanic outgassing and volatile evolution. Volcanic processes are the primary mechanism for release of water and atmospheric gasses that support past and present life and human exploration. Sites of present day volcanism, if any, may be prime sites for the search for life. Requires knowledge of the age and composition of igneous rocks using global imaging, returned samples, chemical analyses, geologic mapping, geochronology, and techniques for distinguishing igneous and sedimentary rocks, and evaluation of current activity from seismic monitoring.

5. Investigation: Characterize surface-atmosphere interactions on Mars, including polar, eolian, chemical, weathering, and mass-wasting processes. Timescales for this investigation are the last million years and the upper 1m to 1 km of geological materials. Understanding present geologic, hydrologic, and atmospheric processes is the key to understanding past environments of Mars and possible locations for near-surface water. This study also has strong implications for resources and hazards for future human exploration. Requires orbital visual and thermal imaging, spectroscopy, and geophysical and topographic sounding, remote analysis of surface sediment composition and mineralogy, lander studies of boundary layer processes, analysis of returned samples, drilling.

6. Investigation: Determine the large-scale vertical structure of the crust and its regional variation. This includes, for example, the structure and origin of hemispheric dichotomy. The vertical and global variation of rock properties and composition places constraints on the distribution of subsurface aquifers and aids interpretation of past igneous and sedimentary processes. Requires interpretation of global imaging and topography, geophysical sounding from orbiters and landers, geologic mapping, analysis in-situ lander data on mineralogy and composition of surface material, returned samples, and seismic monitoring.

7. Investigation: Document the tectonic history of the Martian crust, including present activity. Understanding of the temporal evolution of internal processes places constraints on release of volatiles from differentiation and volcanic activity and the effect of tectonic structures (faults and fractures in particular) on subsurface hydrology. Requires geologic mapping utilizing global topographic data combined with high-resolution imaging, magnetic and gravity data, and seismic monitoring.

8. Investigation: Determine the bulk composition and spatial/temporal evolution of the crust. This provides information on how the planet differentiated and the formation of the planet, with implications for the volatile composition and rate of release to the surface. Requires returned sample of windblown dust and composition of major stratigraphic units, remote analysis of surface mineralogy and composition, analysis of returned samples.

1. Investigation: Characterize the configuration of Mars’ interior. This is needed to understand the origin and thermal evolution of Mars and the relationships to surface evolution and release of water and atmospheric gasses. Requires gravity, topography, rotational dynamics from landers with direct-to-Earth communication, magnetics, long-term seismic network

2. Investigation: Determine the history of the magnetic field. Evidence that Mars had a magnetic field early in its history has important implications for the retention of its early atmosphere and for the shielding of the surface from incoming radiation and the possible evolution of life. Requires measurements of the strength and spatial variation of remanant magnetism from low orbit or aerial platform with global coverage and correlation with information on internal structure and temporal evolution of the Martian interior.

3. Investigation: Determine the thermal evolution of the planet. Knowledge of the thermal evolution places constraints on the composition, quantity, and rate of release of volatiles (water and atmospheric gasses) to the surface. Techniques: in-situ heat flow measurement, results from B1.

4. Investigation: Determine the chemical and thermal evolution of the mantle. Knowledge of the thermal and chemical evolution places constraints on the composition, quantity, and rate of release of volatiles (water and atmospheric gasses) to the surface. Requires composition of surface rocks from remote analysis and returned samples as a probe into the interior, and results from B1.

1. Investigation: Determine the radiation environment at the Martian surface and the shielding properties of the Martian atmosphere. The propagation of high energy particles through the Martian atmosphere must be understood, and the measurement of secondary particles must be made at the surface to determine the buffering (or amplifying) effects of the Martian atmosphere, and the backscatter effects of the regolith. Requires simultaneous monitoring of the radiation in Mars' orbit and at the surface, including the ability to determine the directionality of the neutrons at the surface.

2. Investigation: Determine toxicity/irritant nature of soils. Needed to provide information necessary to develop hazard mitigation strategies to ensure safety of human explorers on the Martian surface. Requires in-situ experiments and returned samples.

3. Investigation: Determine the reactivity/oxidizing effects of Martian soil upon spaceflight materials. Needed to determine the compatibility of human spacecraft and EVA materials with the potentially reactive Martian soil. Requires in-situ experiments and exposed LDEF-type samples returned as part of a sample return mission.

4. Investigation: Determine environmental biohazards. Needed to understand hazards posed to human explorers from indigenous Martian biology. Requires sample return.

5. Investigation: Understand the distribution of accessible water in soils, regolith, and Martian groundwater systems. Water is a principal resource to humans. Requires geophysical investigations, subsurface drilling, and sample analysis.

6. Investigation: Measure atmospheric parameters and variations that affect atmospheric flight. Pressure and density versus altitude, temporal and spatial variations. Requires instrumented aeroentry shells or aerostats.

7. Investigation: Determine electrical effects in the atmosphere. Needed to understand the role of electrical discharge, electrostatic effects, etc. in atmospheric processes, including dust-raising and potential hazards to surface operations. Requires experiments on a lander.

8. Investigation: Measure the engineering properties of the Martian surface. Soil and surface engineering data (bearing strength, angle of repose, geoelectric properties, etc.) Requires in-situ measurements.

9. Investigation: Determine the radiation shielding properties of Martian regolith. Soil and dust from the Martian surface offer a readily available source of shielding material for surface crews. The thickness of the required regolith cover will depend upon the measured shielding properties. Requires an understanding of the regolith composition and/or a lander with the ability to bury sensors at various depths.

10. Investigation: Measure the ability of Martian soil to support plant life. Determine the ability of the indigenous soil to support life, such as plant growth, for future human missions. Requires in-situ measurements or sample return.

1. Investigation: Demonstrate terminal phase hazard avoidance and precision landing. Necessary to decrease the risks associated with soft landing, and to enable pinpoint landing. Requires flight demonstration during terminal descent phase.

2. Investigation: Demonstrate mid-L/D aeroentry /aerocapture vehicle flight. Mid-L/D (0.4-0.8) aeroentry shapes will be required as payload masses increase. Mid-L/D aeroassist increases landed vehicle performance and landing precision. Requires wind tunnel testing and flight demonstration during aeroentry phase of the mission.

3. Investigation: Demonstrate high-Mach parachute deployment and performance. Higher ballistic coefficient entry vehicles will be result from flying more massive landers. This will result in higher parachute deploy speeds, which are beyond the qualification of current parachute systems. Requires high-altitude Earth-based testing and flight demonstration during Mars entry phase.

4. Investigation: Demonstrate in-situ propellant (methane, oxygen) production (ISPP) and in-situ consumables production (ISCP) (fuel cell reagents, oxygen, water, buffer gasses). Components which directly interact with the Martian environment must be evaluated for performance. End-to-end performance can be evaluated by acquisition of local resources, processing, storage and use of end products. Requires in-situ experiment.

5. Investigation: Access and extract water from soils, regolith, and Martian groundwater systems. Water is a principal resource. Requires in-situ operations to determine hydrologic characteristics of aquifers and aquicludes. Requires subsurface drilling.

6. Investigation: Demonstrate deep drilling. The Martian subsurface will provide access to potential resources (e.g., water) as well as providing access to valuable scientific samples. Requires landed demonstration.

1. High capacity power systems to support ISPP activities in support of robotic sample return missions and eventual human support.

2. Communication infrastructure to support robotic missions with high data rates or a need for more continuous communications, and eventual human support.

3. Navigation infrastructure to support precision landings for robotic or human missions.

4. Test drilling equipment to support the search for water, fossil biosignatures, and geologic information.