7.2 Evidence for past water and potential habitability
3 min read•july 22, 2024
Mars once had water, leaving behind clues in its landscape and minerals. , , and ancient lake basins suggest flowing water, while like clays and sulfates indicate water-rock interactions. These features paint a picture of a wetter Martian past.
This evidence of water is crucial for understanding Mars' potential habitability. , , and could have supported life. Subsurface water ice offers hope for future exploration and possibly even current microbial life in protected environments.
Geomorphological Features and Mineralogical Evidence for Past Water on Mars
Geomorphological features of past water
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- Valley networks
- Branching channels resembling river drainage systems on Earth (Nile River)
- Formed by surface runoff from precipitation or groundwater seepage
- Outflow channels
- Large, wide channels originating from chaotic terrains (Kasei Valles)
- Formed by catastrophic flooding events or release of pressurized groundwater
- and
- Sedimentary deposits at the mouths of valleys or channels (Eberswalde Crater)
- Indicate the presence of flowing water and sediment transport
- Paleolakes
- Ancient lake basins identified by inlet and outlet channels, shorelines, and sedimentary deposits (Gale Crater)
- Suggest the presence of standing bodies of water in Mars' past
- Glacial features
- Moraines, eskers, and other landforms associated with glacial activity (Deuteronilus Mensae)
- Indicate the presence of ice and potential meltwater in the past
Mineralogical evidence for water
- Hydrated minerals
- Phyllosilicates (clay minerals)
- Formed by aqueous alteration of volcanic rocks (montmorillonite)
- Indicate long-term interaction between water and rock
- Sulfates
- Formed by evaporation of water or hydrothermal activity (gypsum)
- Suggest the presence of acidic, saline, or hydrothermal water
- Carbonates
- Formed in neutral to alkaline aqueous environments (magnesite)
- Indicate the presence of more habitable water conditions
- Phyllosilicates (clay minerals)
- Hematite spherules (blueberries)
- Formed by precipitation from iron-rich water or alteration of iron-bearing minerals
- Suggest the presence of liquid water and oxidizing conditions (Meridiani Planum)
- Geochemical evidence from rover missions
- Elemental and isotopic compositions consistent with aqueous alteration
- Indicate the interaction between water and rock, potentially favorable for habitability (Yellowknife Bay)
Habitability Potential and Significance of Water on Mars
Past habitable environments on Mars
- Liquid water
- Essential for life as a solvent and medium for biochemical reactions
- Geomorphological and mineralogical evidence suggests the presence of liquid water in Mars' past
- Energy sources
- Chemical energy from redox gradients in aqueous environments (sulfur-iron reactions)
- Potential for chemotrophic microbial life
- Organic compounds
- Building blocks for life (amino acids, nucleobases)
- Detected in small quantities by rover missions, indicating potential for prebiotic chemistry
- Neutral to alkaline pH
- More favorable for life compared to acidic conditions (pH 7-8)
- Presence of carbonates and phyllosilicates suggests the existence of habitable water conditions
- Protection from radiation
- Subsurface environments, such as caves or deep groundwater, provide shielding from harmful radiation (cosmic rays, UV)
- Potentially more habitable than surface environments
Subsurface water ice for exploration
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- Substantial amounts of water ice detected in the Martian subsurface, particularly at mid to high latitudes ()
- Radar evidence for liquid water beneath the South Polar Layered Deposits
- Resource for human exploration
- Water ice can be extracted and purified for drinking, hygiene, and agriculture
- Electrolysis of water can produce oxygen for breathing and hydrogen for fuel
- Implications for habitability
- Subsurface water ice may provide a potential habitat for microbial life ()
- Melting of ice could create transient liquid water environments
- Accessibility
- Future missions can target water ice reservoirs for in-situ resource utilization (ISRU)
- Subsurface drilling and extraction technologies need to be developed for efficient access to water ice ()
Key Terms to Review (12)
Alluvial Fans: Alluvial fans are fan-shaped deposits of sediment that form where a stream or river slows down and spreads out, typically at the base of a mountain range or hill. They indicate areas where water has previously flowed, and their formation is closely linked to the historical presence of water, making them crucial for understanding past environments and assessing potential habitability of extraterrestrial bodies.
Deltas: Deltas are landforms created at the mouth of a river where it meets a body of water, such as an ocean, sea, or lake, resulting from sediment deposition. These formations are crucial for understanding past water flow and environmental conditions, as they often hold evidence of ancient ecosystems and may indicate areas where life could have thrived, making them important in evaluating potential habitability on other planets.
Energy sources: Energy sources refer to the various origins of energy that can sustain biological processes, which are crucial for life. In astrobiology, understanding these energy sources helps evaluate the habitability of extraterrestrial environments, as different forms of energy can drive metabolic processes and influence the potential for life in diverse settings.
ExoMars Drill: The ExoMars Drill is a scientific instrument designed for the ExoMars rover mission, which aims to search for signs of past life on Mars by drilling into the Martian soil and subsurface. This drill will enable the extraction of samples from up to two meters below the surface, allowing scientists to analyze materials that may have been shielded from harsh environmental conditions and better understand Mars' potential habitability.
Hydrated minerals: Hydrated minerals are minerals that contain water molecules within their crystal structure, often influencing their physical and chemical properties. The presence of water in these minerals can indicate past environmental conditions, including the availability of liquid water, which is essential for potential habitability on planets or moons. Understanding hydrated minerals helps scientists interpret geological history and assess the likelihood of life-supporting environments elsewhere in the solar system.
Liquid water: Liquid water is a state of H2O that exists between 0°C and 100°C at standard atmospheric pressure, crucial for supporting life as we know it. It serves as a universal solvent, facilitates biochemical reactions, and is vital for transporting nutrients and waste in living organisms.
Organic Compounds: Organic compounds are molecules primarily composed of carbon atoms, often combined with hydrogen, oxygen, nitrogen, and other elements. These compounds are the building blocks of life and play essential roles in biochemical processes, making them a key focus in the search for extraterrestrial life and the study of habitability in various celestial environments.
Outflow Channels: Outflow channels are large, ancient river-like features on the surface of Mars that indicate the past movement of water. These channels suggest that liquid water once flowed across the Martian landscape, leading to theories about the planet's potential habitability and its climatic history. The presence of outflow channels offers critical insights into the processes that may have shaped Mars and how conditions might have been suitable for life.
Psychrophiles: Psychrophiles are a group of extremophilic organisms that thrive at low temperatures, typically at or below 15°C (59°F). These organisms have adapted to survive and grow in icy environments such as polar regions, deep ocean waters, and glaciers, showcasing the incredible diversity of life on Earth. Their existence provides insights into potential life forms that could exist in similar extreme environments on other planets or moons.
Utopia Planitia: Utopia Planitia is a vast plain located on the surface of Mars, known for its geological features and evidence of past water activity. This region is significant in the study of Mars' history as it suggests potential habitability and may have once harbored conditions suitable for life. The discovery of various landforms, such as outflow channels and possible lake beds in Utopia Planitia, points to the presence of liquid water in the planet's past.
Valley networks: Valley networks are a series of interconnected channels and valleys that resemble river drainage systems, typically found on the surface of planets and moons, notably Mars. These features are significant because they provide strong evidence of past fluvial processes, indicating the presence of liquid water and suggesting conditions that may have supported habitability in the past.
Water ice reservoirs: Water ice reservoirs refer to regions where water exists in solid ice form, typically found in the polar caps, beneath the surface, or in permanently shadowed craters on celestial bodies like Mars and the Moon. These reservoirs are crucial for understanding the history of water on these bodies and evaluating their potential for habitability by supporting future human exploration or microbial life.