{
  "spore": "profile",
  "id": "water",
  "spore_version": "0.2",
  "family": "water",
  "name": "Water",
  "abbreviation": "H2O",
  "role": "hydrogen-rich radiation shield and potable fluid",
  "category": "shielding",
  "type": "water-and-ice",
  "summary": "Liquid water has a density of 999.79 kg/m3 at 0.028556 °C in the NIST saturation table, and it holds 4.2198 J/(g*K) of heat capacity at the same point. Water is 11.19% hydrogen by mass (calculated from NIST atomic weights). A 2013 NASA Langley analysis found that a single heavy-lift launch of water could protect astronauts for a 130-day deep-space mission before the 150 mSv design limit was exceeded, under the 1977 galactic cosmic ray environment. That result is an analysis, not a flight test. Water is also the potable water that the International Space Station stores and treats with biocides.\n",
  "best_for": "Hydrogen-rich shielding for crew areas that already hold potable water (NASA Langley analysis, 2013; ISS potable water practice, ICES 2023)",
  "weakest_at": "Freezing: water expands on freezing (PubChem), and stored water needs a biocide to stay free of microbes and biofilm (NASA ICES 2025)",
  "identity": {
    "formula": "H2O",
    "cas": "7732-18-5",
    "designations": [],
    "source": "pubchem-water",
    "where": "Names and Identifiers (CID 962, CAS 7732-18-5); molecular formula H2O from the PubChem compound record"
  },
  "tags": {
    "environments": [
      "deep-space"
    ],
    "stresses": [
      "total-radiation-dose"
    ],
    "applications": [
      "radiation-shielding",
      "habitats-and-suits"
    ]
  },
  "properties": [
    {
      "benchmark": "density",
      "label": "Density of saturated liquid water near 0 °C",
      "value": 999.79,
      "bound": "exact",
      "unit": "kg/m3",
      "scope": "material",
      "conditions": {
        "state": "saturated liquid",
        "temperature": "0.028556 °C (first printed row of the saturation table)",
        "pressure": "0.00061248 MPa (saturation pressure as printed)"
      },
      "method": "Value copied from the NIST Chemistry WebBook saturation table",
      "status": "ground",
      "source": "nist-sat",
      "where": "Saturation properties table, row 1, Density (kg/m3) column",
      "source_detail": {
        "title": "NIST Chemistry WebBook, water: saturation properties table",
        "id": "NIST SRD 69; CAS 7732-18-5",
        "url": "https://webbook.nist.gov/cgi/fluid.cgi?ID=C7732185&Type=SatT&Digits=5&PLow=&PHigh=&PInc=&T=25&RefState=DEF&TUnit=C&PUnit=MPa&DUnit=kg%2Fm3&HUnit=kJ%2Fkg&WUnit=m%2Fs&VisUnit=uPa*s&STUnit=N%2Fm&Action=Load",
        "year": 2026,
        "kind": "database",
        "license": "US government work (NIST)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density of liquid water at 0 °C/4 °C, PubChem",
      "value": 0.999868,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "state": "liquid",
        "basis": "printed as 0.999868 at 0 °C/4 °C (liquid)"
      },
      "method": "Experimental density value printed in the PubChem record",
      "status": "ground",
      "source": "pubchem-water",
      "where": "Chemical and Physical Properties, Experimental Properties, Density entry",
      "source_detail": {
        "title": "PubChem compound record: Water (CID 962)",
        "id": "CID 962; CAS 7732-18-5",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Water",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density of liquid water at 25 °C, PubChem",
      "value": 0.995,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "state": "liquid",
        "temperature": "25 °C"
      },
      "method": "Experimental density value printed in the PubChem record",
      "status": "ground",
      "note": "The 25 °C figure was not checked against a second source. It is lower than the NIST value near 0 °C, and the two temperatures differ, so they are not compared directly.",
      "source": "pubchem-water",
      "where": "Chemical and Physical Properties, Experimental Properties, Density entry (first value)",
      "source_detail": {
        "title": "PubChem compound record: Water (CID 962)",
        "id": "CID 962; CAS 7732-18-5",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Water",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "density",
      "label": "Density of ice at 0 °C",
      "value": 0.917,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "phase": "ice",
        "temperature": "0 °C"
      },
      "method": "Experimental density value printed in the PubChem record",
      "status": "ground",
      "source": "pubchem-water",
      "where": "Chemical and Physical Properties, Experimental Properties, Density entry (ice value)",
      "source_detail": {
        "title": "PubChem compound record: Water (CID 962)",
        "id": "CID 962; CAS 7732-18-5",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Water",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point of ice and water",
      "value": 0,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "pressure": "not stated in the source"
      },
      "method": "Value printed in the PubChem experimental melting point entry",
      "status": "ground",
      "source": "pubchem-water",
      "where": "Chemical and Physical Properties, Experimental Properties, Melting Point",
      "source_detail": {
        "title": "PubChem compound record: Water (CID 962)",
        "id": "CID 962; CAS 7732-18-5",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Water",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "boiling_point",
      "label": "Boiling point, PubChem",
      "value": 99.974,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "pressure": "not stated for this value; the same PubChem record gives 212 °F at 760 mmHg"
      },
      "method": "Value printed in the PubChem experimental boiling point entry",
      "status": "ground",
      "source": "pubchem-water",
      "where": "Chemical and Physical Properties, Experimental Properties, Boiling Point",
      "source_detail": {
        "title": "PubChem compound record: Water (CID 962)",
        "id": "CID 962; CAS 7732-18-5",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Water",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "boiling_point",
      "label": "Boiling point, NIST average",
      "value": 373.17,
      "bound": "exact",
      "unit": "K",
      "scope": "material",
      "conditions": {
        "pressure": "not stated on the page",
        "uncertainty": "±0.04 K, average of 7 values"
      },
      "method": "Value printed in the NIST phase change data",
      "status": "ground",
      "note": "NIST gives 373.17 K, which is about 0.05 °C above the PubChem value of 99.974 °C. Both are kept as printed.",
      "source": "nist-webbook",
      "where": "Phase change data, Tboil",
      "source_detail": {
        "title": "NIST Chemistry WebBook, water: phase change data",
        "id": "NIST SRD 69; CAS 7732-18-5",
        "url": "https://webbook.nist.gov/cgi/cbook.cgi?ID=C7732185&Units=SI&Mask=4#Thermo-Phase",
        "year": 2026,
        "kind": "database",
        "license": "US government work (NIST)"
      }
    },
    {
      "benchmark": "critical_temperature",
      "label": "Critical temperature, NIST average",
      "value": 647,
      "bound": "exact",
      "unit": "K",
      "scope": "material",
      "conditions": {
        "uncertainty": "±2 K, average of 7 values"
      },
      "method": "Value printed in the NIST phase change data",
      "status": "ground",
      "source": "nist-webbook",
      "where": "Phase change data, Tc",
      "source_detail": {
        "title": "NIST Chemistry WebBook, water: phase change data",
        "id": "NIST SRD 69; CAS 7732-18-5",
        "url": "https://webbook.nist.gov/cgi/cbook.cgi?ID=C7732185&Units=SI&Mask=4#Thermo-Phase",
        "year": 2026,
        "kind": "database",
        "license": "US government work (NIST)"
      }
    },
    {
      "benchmark": "critical_temperature",
      "label": "Critical temperature, PubChem",
      "value": 374.2,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "printed in the PubChem safety and hazard properties section"
      },
      "method": "Value printed in the PubChem record",
      "status": "ground",
      "note": "The PubChem value of 374.2 °C differs from the NIST value of 647 K (about 373.9 °C). Both are kept as printed.",
      "source": "pubchem-water",
      "where": "Safety and Hazards, Safety and Hazard Properties, Critical Temperature and Pressure",
      "source_detail": {
        "title": "PubChem compound record: Water (CID 962)",
        "id": "CID 962; CAS 7732-18-5",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Water",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "critical_pressure",
      "label": "Critical pressure, NIST",
      "value": 220.64,
      "bound": "exact",
      "unit": "bar",
      "scope": "material",
      "conditions": {
        "basis": "NIST gives the value from Sato, Watanabe et al. (1991); other sources in the NIST table list 220.60, 220.46 and 220.64 bar"
      },
      "method": "Value printed in the NIST phase change data",
      "status": "ground",
      "source": "nist-webbook",
      "where": "Phase change data, Pc",
      "source_detail": {
        "title": "NIST Chemistry WebBook, water: phase change data",
        "id": "NIST SRD 69; CAS 7732-18-5",
        "url": "https://webbook.nist.gov/cgi/cbook.cgi?ID=C7732185&Units=SI&Mask=4#Thermo-Phase",
        "year": 2026,
        "kind": "database",
        "license": "US government work (NIST)"
      }
    },
    {
      "benchmark": "critical_pressure",
      "label": "Critical pressure, PubChem",
      "value": 218,
      "bound": "exact",
      "unit": "atm",
      "scope": "material",
      "conditions": {
        "basis": "printed in the PubChem safety and hazard properties section"
      },
      "method": "Value printed in the PubChem record",
      "status": "ground",
      "note": "The PubChem value of 218 atm differs from the NIST value of 220.64 bar (about 217.8 atm). Both are kept as printed.",
      "source": "pubchem-water",
      "where": "Safety and Hazards, Safety and Hazard Properties, Critical Temperature and Pressure",
      "source_detail": {
        "title": "PubChem compound record: Water (CID 962)",
        "id": "CID 962; CAS 7732-18-5",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Water",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "specific_heat",
      "label": "Isobaric heat capacity of saturated liquid water near 0 °C",
      "value": 4.2198,
      "bound": "exact",
      "unit": "J/(g*K)",
      "scope": "material",
      "conditions": {
        "state": "saturated liquid",
        "temperature": "0.028556 °C (first printed row)",
        "pressure": "saturation"
      },
      "method": "Value copied from the NIST saturation table, Cp column",
      "status": "ground",
      "source": "nist-sat",
      "where": "Saturation properties table, row 1, Cp (J/g*K) column",
      "source_detail": {
        "title": "NIST Chemistry WebBook, water: saturation properties table",
        "id": "NIST SRD 69; CAS 7732-18-5",
        "url": "https://webbook.nist.gov/cgi/fluid.cgi?ID=C7732185&Type=SatT&Digits=5&PLow=&PHigh=&PInc=&T=25&RefState=DEF&TUnit=C&PUnit=MPa&DUnit=kg%2Fm3&HUnit=kJ%2Fkg&WUnit=m%2Fs&VisUnit=uPa*s&STUnit=N%2Fm&Action=Load",
        "year": 2026,
        "kind": "database",
        "license": "US government work (NIST)"
      }
    },
    {
      "benchmark": "dynamic_viscosity",
      "label": "Dynamic viscosity of saturated liquid water near 0 °C",
      "value": 1790.2,
      "bound": "exact",
      "unit": "uPa*s",
      "scope": "material",
      "conditions": {
        "state": "saturated liquid",
        "temperature": "0.028556 °C (first printed row)"
      },
      "method": "Value copied from the NIST saturation table, Viscosity column",
      "status": "ground",
      "note": "Snake-case name; this property is not in spores/property-canon.yaml.",
      "source": "nist-sat",
      "where": "Saturation properties table, row 1, Viscosity (uPa*s) column",
      "source_detail": {
        "title": "NIST Chemistry WebBook, water: saturation properties table",
        "id": "NIST SRD 69; CAS 7732-18-5",
        "url": "https://webbook.nist.gov/cgi/fluid.cgi?ID=C7732185&Type=SatT&Digits=5&PLow=&PHigh=&PInc=&T=25&RefState=DEF&TUnit=C&PUnit=MPa&DUnit=kg%2Fm3&HUnit=kJ%2Fkg&WUnit=m%2Fs&VisUnit=uPa*s&STUnit=N%2Fm&Action=Load",
        "year": 2026,
        "kind": "database",
        "license": "US government work (NIST)"
      }
    },
    {
      "benchmark": "surface_tension",
      "label": "Surface tension of water at 25 °C",
      "value": 71.97,
      "bound": "exact",
      "unit": "dyne/cm",
      "scope": "material",
      "conditions": {
        "temperature": "25 °C"
      },
      "method": "Value printed in the PubChem experimental surface tension entry",
      "status": "ground",
      "source": "pubchem-water",
      "where": "Chemical and Physical Properties, Experimental Properties, Surface Tension",
      "source_detail": {
        "title": "PubChem compound record: Water (CID 962)",
        "id": "CID 962; CAS 7732-18-5",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Water",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "vapor_pressure",
      "label": "Vapor pressure of water at 273.16 K",
      "value": 611.657,
      "bound": "exact",
      "unit": "Pa",
      "scope": "material",
      "conditions": {
        "temperature": "273.16 K"
      },
      "method": "Value printed in the PubChem experimental vapor pressure entry",
      "status": "ground",
      "note": "Snake-case name; this property is not in spores/property-canon.yaml.",
      "source": "pubchem-water",
      "where": "Chemical and Physical Properties, Experimental Properties, Vapor Pressure (VP: 611.657 Pa at 273.16 K)",
      "source_detail": {
        "title": "PubChem compound record: Water (CID 962)",
        "id": "CID 962; CAS 7732-18-5",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Water",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "refractive_index",
      "label": "Refractive index of water",
      "value": 1.333,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "temperature": "not stated in the source",
        "wavelength": "not stated in the source"
      },
      "method": "Value printed in the PubChem refractive index entry",
      "status": "ground",
      "source": "pubchem-water",
      "where": "Chemical and Physical Properties, Experimental Properties, Refractive Index",
      "source_detail": {
        "title": "PubChem compound record: Water (CID 962)",
        "id": "CID 962; CAS 7732-18-5",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Water",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "temperature_of_max_density",
      "label": "Temperature of maximum density of liquid water",
      "value": 3.98,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "printed as the temperature of maximum density in the PubChem density entry"
      },
      "method": "Value printed in the PubChem record",
      "status": "ground",
      "note": "Snake-case name; this property is not in spores/property-canon.yaml.",
      "source": "pubchem-water",
      "where": "Chemical and Physical Properties, Experimental Properties, Density entry (Temp of max density 3.98 °C)",
      "source_detail": {
        "title": "PubChem compound record: Water (CID 962)",
        "id": "CID 962; CAS 7732-18-5",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Water",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "hydrogen_mass_fraction",
      "label": "Hydrogen share of the mass of water",
      "value": 11.19,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "basis": "2 hydrogen atoms in H2O divided by the molecular weight 18.015 g/mol, with hydrogen taken as 1.008 g/mol"
      },
      "method": "Calculated by Space Mushroom: 2 x 1.008 / 18.015 = 11.19%. The NIST atomic weight of hydrogen is printed as the interval [1.007 84, 1.008 11], which gives the same 11.19% to two decimals.",
      "status": "calculated",
      "note": "Snake-case name; this property is not in spores/property-canon.yaml.",
      "source": "nist-atomic",
      "where": "Standard atomic weight table, H row (interval printed); PubChem molecular weight 18.015 g/mol",
      "source_detail": {
        "title": "Atomic weights and isotopic compositions: hydrogen and oxygen (NIST)",
        "id": "NIST standard atomic weights",
        "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=H&all=all&ascii=html&isotype=some",
        "year": 2026,
        "kind": "database",
        "license": "US government work (NIST)"
      }
    },
    {
      "benchmark": "protection_time",
      "label": "Protection time from a single heavy-lift launch of water",
      "value": 130,
      "bound": "exact",
      "unit": "days",
      "scope": "material",
      "conditions": {
        "environment": "1977 galactic cosmic ray environment",
        "exposure_limit": "150 mSv design basis",
        "launch": "single heavy-lift launch of pure shielding mass, under the paper's assumptions"
      },
      "method": "Analysis result stated in the paper abstract; not a measurement",
      "status": "calculated",
      "note": "Snake-case name; this property is not in spores/property-canon.yaml. The same abstract gives 160 days for liquid hydrogen and says a single launch of polyethylene gives the same 130 days. The same abstract also says that liquid hydrogen is not the best shield per unit mass compared with polyethylene for missions longer than 225 days.",
      "source": "singleterry2013",
      "where": "Abstract",
      "source_detail": {
        "title": "Radiation Engineering Analysis of Shielding Materials to Assess Their Ability to Protect Astronauts in Deep Space From Energetic Particle Radiation",
        "id": "NTRS 20140003150; doi:10.1016/j.actaastro.2013.04.013 (Acta Astronautica 91)",
        "url": "https://ntrs.nasa.gov/citations/20140003150",
        "year": 2013,
        "kind": "paper",
        "license": "public domain (NASA)"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Potable water held in spacecraft storage and distribution lines (microbial growth)",
      "headline": "Stored potable water needs a biocide to control microbes, biofilm and microbially influenced corrosion.",
      "effect": "NASA's 2025 ICES paper states that a potable-water biocide should prevent or control microbial growth, prevent or limit biofilm formation, and prevent microbiologically influenced corrosion. The target dose is 200 to 400 parts per billion of silver ion (Ag+), chosen with the Spacecraft Water Exposure Guidelines for 1000-day missions as the upper limit.",
      "rating": "moderate",
      "conditions": {
        "biocide": "silver ion (Ag+)",
        "target_range": "200 to 400 ppb Ag+",
        "basis": "upper limit set by the Spacecraft Water Exposure Guidelines for 1000-day missions"
      },
      "source": "irwin2025",
      "where": "Introduction, requirements paragraph; Silver biocide section, target range paragraph"
    },
    {
      "environment": "Iodine-disinfected potable water on the International Space Station",
      "headline": "Iodine must be removed at the dispenser before crew consumption; silver does not need removal.",
      "effect": "NASA's 2025 ICES paper states that, unlike iodine, silver ion biocide does not need to be removed at the potable water dispenser, and that Ag+ is effective at levels below 400 ppb that are safe for human consumption. The 2023 ICES paper compares iodine and silver for ISS potable water and identifies gaps in knowledge.",
      "rating": "low",
      "conditions": {
        "biocide": "molecular iodine (ISS) versus silver ion (Ag+)"
      },
      "source": "irwin2025",
      "where": "Silver biocide introduction paragraph"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "PubChem reports that water does not meet GHS hazard criteria in 1,866 of 1,876 company reports (99.5%); the record's aggregated ECHA notifications give the same picture.",
        "ghs": [],
        "source": "pubchem-water",
        "where": "Safety and Hazards, GHS Classification (note line)"
      },
      {
        "text": "PubChem's health-hazard section states that water itself is nontoxic; hazards come from substances dissolved in it.",
        "ghs": [],
        "source": "pubchem-water",
        "where": "Safety and Hazards, Hazards Identification, Health Hazards"
      }
    ],
    "failure_risks": [
      {
        "mode": "Freezing of stored water",
        "trigger": "Temperature at or below 0 °C",
        "consequence": "PubChem notes that water expands on freezing; its ice density is 0.917 g/cm3 at 0 °C. Damage to tanks or lines is not measured in any source read here.",
        "severity": "moderate",
        "source": "pubchem-water",
        "where": "Chemical and Physical Properties, Density entry"
      },
      {
        "mode": "Microbial growth in stored potable water",
        "trigger": "Storage without an effective biocide",
        "consequence": "NASA's 2025 ICES paper lists microbial growth, biofilm and microbially influenced corrosion as what a potable-water biocide must prevent.",
        "severity": "moderate",
        "source": "irwin2025",
        "where": "Introduction, requirements paragraph"
      }
    ],
    "side_effects": [
      {
        "text": "NASA's 2025 ICES paper notes that, unlike silver, iodine must be removed at the potable water dispenser before crew consumption.",
        "affects": "Crew drinking water at the dispenser",
        "source": "irwin2025",
        "where": "Silver biocide introduction paragraph"
      }
    ],
    "handling": [
      {
        "text": "Keep stored potable water treated with a biocide; NASA's 2025 requirements call for control of microbes and biofilm.",
        "source": "irwin2025",
        "where": "Introduction, requirements paragraph"
      },
      {
        "text": "Keep stored water from freezing, because it expands when it freezes (PubChem).",
        "source": "pubchem-water",
        "where": "Chemical and Physical Properties, Density entry"
      }
    ],
    "mitigations": [
      {
        "text": "Silver ion biocide is targeted at 200 to 400 ppb; unlike iodine, silver needs no removal at the dispenser.",
        "source": "irwin2025",
        "where": "Silver biocide section, target range paragraph"
      }
    ]
  },
  "uses": [
    {
      "application": "radiation-shielding",
      "device": "Deep-space crew shielding (analysis only)",
      "example": "A NASA Langley analysis found that a single heavy-lift launch of water or polyethylene could protect astronauts for a 130-day mission before exceeding the 150 mSv design basis exposure, under the 1977 galactic cosmic ray environment.",
      "source": "singleterry2013",
      "where": "Abstract"
    },
    {
      "application": "radiation-shielding",
      "device": "Deep-space vehicle with permanent on-board water storage (modelling thesis)",
      "example": "A 2018 Cal Poly master's thesis on utilizing permanent on-board water storage for deep-space radiation shielding concludes that the permanent inclusion of water gives added support against galactic cosmic rays and solar particle events; the abstract gives no numbers.",
      "source": "gehrke2018",
      "where": "Abstract (title and conclusion)"
    },
    {
      "application": "habitats-and-suits",
      "device": "International Space Station potable water system (drinking, hygiene and technical water)",
      "example": "Molecular iodine and ionic silver have been used on the International Space Station for decades to control microbes in potable water, and the 2023 ICES paper compares the two biocides for drinking, hygiene, technical, oxygen-generation and extravehicular activity water.",
      "source": "muirhead2023",
      "where": "Abstract"
    }
  ],
  "supply": [
    {
      "subject": "Water (H2O), abundance on Earth",
      "abundance": "About 1,386 million km3 (332.5 million mi3) of water on Earth; the oceans hold about 96.5% of it (USGS). Of freshwater, over 68% is in ice and glaciers, and about 30% is in the ground (USGS).",
      "producers": [],
      "critical_lists": [],
      "recycling": "Not found in any source we hold.",
      "substitutes": [],
      "source": "usgs-water",
      "where": "How much water is there on Earth: Overview; Where is Earth's water located; data table (percent of freshwater)"
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "NIST Chemistry WebBook: water, saturation and phase change data",
      "type": "database",
      "url": "https://webbook.nist.gov/cgi/cbook.cgi?ID=C7732185&Units=SI&Mask=4#Thermo-Phase",
      "year": 2026
    },
    {
      "title": "NIST Chemistry WebBook: water, saturation properties table",
      "type": "database",
      "url": "https://webbook.nist.gov/cgi/fluid.cgi?ID=C7732185&Type=SatT&Digits=5&PLow=&PHigh=&PInc=&T=25&RefState=DEF&TUnit=C&PUnit=MPa&DUnit=kg%2Fm3&HUnit=kJ%2Fkg&WUnit=m%2Fs&VisUnit=uPa*s&STUnit=N%2Fm&Action=Load",
      "year": 2026
    },
    {
      "title": "NIST atomic weights: hydrogen and oxygen",
      "type": "database",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=H&all=all&ascii=html&isotype=some",
      "year": 2026
    },
    {
      "title": "PubChem: Water (CID 962)",
      "type": "database",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Water",
      "year": 2026
    },
    {
      "title": "Singleterry, Radiation Engineering Analysis of Shielding Materials (NASA Langley; Acta Astronautica 91, 2013)",
      "type": "paper",
      "url": "https://ntrs.nasa.gov/citations/20140003150",
      "year": 2013
    },
    {
      "title": "Irwin et al., Silver Foam: Long-Term Passive Dosing of Biocide, Update 2025 (ICES-2025-194)",
      "type": "paper",
      "url": "https://ntrs.nasa.gov/api/citations/20250005545/downloads/ICES-2025-194.pdf",
      "year": 2025
    },
    {
      "title": "Muirhead et al., Evaluation of Iodine and Silver as Biocides for Potable Water (ICES 2023)",
      "type": "paper",
      "url": "https://ntrs.nasa.gov/api/citations/20220015620/downloads/ICES%202023%20Abstract%20Iodine%20and%20Silver%20for%20Strives.pdf",
      "year": 2023
    },
    {
      "title": "Gehrke, Utilizing Permanent On-Board Water Storage for Efficient Deep Space Radiation Shielding (Cal Poly thesis)",
      "type": "paper",
      "url": "https://digitalcommons.calpoly.edu/theses/1933",
      "year": 2018
    },
    {
      "title": "USGS Water Science School: How much water is there on Earth?",
      "type": "report",
      "url": "https://www.usgs.gov/special-topics/water-science-school/science/how-much-water-there-earth",
      "year": 2026
    }
  ],
  "gaps": [
    "No flight or space-environment measurement of water as a radiation shield was found in the sources read here. The 130-day figure is an analysis result from one 2013 paper, and only its abstract was read.",
    "No neutron or galactic cosmic ray dose per unit areal density for water was read from a page. The NIST table covers photons (X-ray and gamma) only.",
    "The Cal Poly thesis PDF returned HTTP 403 when downloaded, so only its abstract was read. Its Orion-related modelling numbers are not in this profile.",
    "Supply: water is not a mined commodity. No producer shares, critical-mineral listing or recycling figure for water was found in a source we hold; the USGS mineral chapters do not cover it.",
    "No room-temperature (20 to 25 °C) liquid density, heat capacity or viscosity from NIST was read. The fetched NIST saturation table printed its first saturated-liquid row at 0.028556 °C, and the 25 °C value was not in the copy we read.",
    "NIST liquid thermal conductivity in the saturation table (0.55565 W/(m*K) in row 1) was left out because no second source for it was read in this run.",
    "Ice properties beyond density (heat of fusion, thermal conductivity, expansion coefficient) were not read from a source.",
    "Critical temperature and pressure disagree between NIST and PubChem; both are kept as printed, and neither was checked against a third source.",
    "Biocide depletion over the storage life of stored water was not read on a fetched page and is not stated here.",
    "Freezing damage to tanks or lines has no test result in any source read here; the damage risk is an inference from the PubChem note that water expands on freezing.",
    "Hazard data rest on the PubChem record (aggregated ECHA notifications). No supplier safety data sheet for water was read.",
    "Snake-case names used for properties not in spores/property-canon.yaml: dynamic_viscosity, vapor_pressure, temperature_of_max_density, hydrogen_mass_fraction, protection_time, critical_temperature and critical_pressure (the last two may already be aliases; check before import).",
    "No media, images or CSV added in this profile."
  ],
  "story": {
    "why": "Water is a hydrogen-rich material that the International Space Station already stores as potable water (ICES 2023). A 2013 NASA Langley analysis found that a single heavy-lift launch of water could protect astronauts for a 130-day deep-space mission under its assumptions, the same as polyethylene. A 2018 Cal Poly thesis concludes that permanent on-board water storage adds protection against galactic cosmic rays and solar particle events; its abstract gives no numbers. The shielding figures are analysis results, not flight measurements.",
    "uses": [
      {
        "where": "Deep-space crew shielding (analysis)",
        "line": "A NASA Langley analysis found that a single heavy-lift launch of water could protect astronauts for a 130-day mission before the 150 mSv design basis was exceeded, under the 1977 galactic cosmic ray environment."
      },
      {
        "where": "Potable water on the International Space Station",
        "line": "Iodine and silver biocides have been used on the International Space Station to control microbes in potable water. A 2023 ICES paper compares them for drinking, hygiene, technical, oxygen-generation and extravehicular activity water."
      }
    ],
    "can_do": [
      {
        "label": "Radiation shielding",
        "line": "A single heavy-lift launch of water can protect astronauts for a 130-day mission under the 1977 galactic cosmic ray environment, before the 150 mSv design basis is exceeded (NASA Langley analysis, 2013).",
        "benchmark": "protection_time",
        "scope": "material",
        "value": "130 days"
      },
      {
        "label": "Heat capacity",
        "line": "Saturated liquid water has an isobaric heat capacity of 4.2198 J/(g*K) at 0.028556 °C, per the NIST saturation table.",
        "benchmark": "specific_heat",
        "scope": "material",
        "value": "4.2198 J/(g*K)"
      },
      {
        "label": "Liquid range at 1 atm",
        "line": "Liquid water runs from its melting point of 0 °C to its boiling point of 99.974 °C, as printed by PubChem; the record gives the boiling point without its pressure, and the same record gives 212 °F at 760 mmHg.",
        "scope": "material",
        "value": "0 °C to 99.974 °C"
      }
    ],
    "compare": "Per launch, the 2013 NASA Langley analysis finds that water and polyethylene protect astronauts for the same 130-day mission under its assumptions. The same abstract gives 160 days for liquid hydrogen and says that liquid hydrogen is not the best shield per unit mass compared with polyethylene for missions longer than 225 days. These are analysis results for the 1977 galactic cosmic ray environment, not measurements. The NIST table gives only the photon (X-ray and gamma) attenuation of water, so it does not show how water compares for galactic cosmic rays.",
    "compare_rows": [
      {
        "label": "Density, liquid near 0 °C",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Hydrogen mass fraction",
        "benchmark": "hydrogen_mass_fraction",
        "scope": "material"
      }
    ],
    "handling": [
      "Keep stored potable water treated with a biocide; NASA's 2025 requirements call for control of microbes and biofilm.",
      "Keep water from freezing in a shield or line, because it expands when it freezes (PubChem).",
      "Silver ion biocide is targeted at 200 to 400 ppb; unlike iodine, silver needs no removal at the dispenser (ICES 2025)."
    ],
    "good_for": [
      "Hydrogen-rich shielding in crew areas where potable water is already stored (NASA Langley, 2013; ICES 2023).",
      "A well-characterised heat capacity: 4.2198 J/(g*K) for saturated liquid near 0 °C (NIST)."
    ],
    "watch_out": [
      "Freezing: water expands when it freezes (PubChem), and no source read here tests what that does to a tank.",
      "Biological growth: stored water needs a biocide (NASA ICES 2025).",
      "The 130-day protection figure is a 2013 analysis under stated assumptions, not a flight test."
    ],
    "verdict": "Water is a practical hydrogen-rich shield for crew areas that already hold potable water. Its shielding value rests on a 2013 analysis, not on a flight test, and it must be kept from freezing and from microbes.",
    "recipe": {
      "line": "Water is H2O: one oxygen atom bonded covalently to two hydrogen atoms (PubChem, CAS 7732-18-5). Its molecular weight is 18.015 g/mol (PubChem). Water is not mined; it is the liquid that the shield and the potable water system store.",
      "parts": [
        {
          "name": "Hydrogen",
          "symbol": "H",
          "role": "Two hydrogen atoms per molecule. Hydrogen makes up 11.19% of the mass of water (calculated; see properties). NIST prints the standard atomic weight of hydrogen as an interval, so no single value is given here."
        },
        {
          "name": "Oxygen",
          "symbol": "O",
          "role": "One oxygen atom per molecule; the rest of the mass of water. NIST prints the standard atomic weight of oxygen as an interval, so no single value is given here."
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "Water is not classified as hazardous in the PubChem record: 1,866 of 1,876 company reports (99.5%) say it does not meet GHS hazard criteria.",
        "points": [
          {
            "label": "The liquid",
            "line": "PubChem's health-hazard section says that water itself is nontoxic. Hazards come from substances dissolved in it, which have their own records."
          },
          {
            "label": "Biological growth",
            "line": "Stored water needs a biocide to control microbes, biofilm and microbially influenced corrosion, according to NASA's 2025 ICES paper."
          }
        ],
        "level": 0,
        "verdict": "Not classified hazardous"
      },
      {
        "title": "If water freezes in a shield or line",
        "lead": "Freezing is a physical hazard for stored water. No source read here tests what it does to a tank.",
        "points": [
          {
            "label": "Expansion",
            "line": "PubChem notes that water expands on freezing. Its ice density is 0.917 g/cm3 at 0 °C, while liquid water is 0.999868 g/cm3 at 0 °C/4 °C."
          },
          {
            "label": "Damage",
            "line": "Damage to tanks or lines from freezing is an inference from the expansion note. No test in the sources read here measured it."
          }
        ]
      },
      {
        "title": "Handling and storage",
        "points": [
          {
            "label": "Biocide",
            "line": "NASA's 2025 ICES paper targets 200 to 400 ppb of silver ion (Ag+) for stored potable water, and states that Ag+ is effective below 400 ppb and safe for human consumption at that level."
          },
          {
            "label": "Iodine",
            "line": "Unlike silver, iodine must be removed at the potable water dispenser before crew consumption, according to the same 2025 paper."
          }
        ]
      }
    ]
  },
  "updated": "2026-11-01",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 19,
    "unreachable": 12,
    "caveats": 3,
    "note": "Written by an AI assistant on 2026-11-01 from NIST, PubChem, USGS and NASA pages read in that run. The Cal Poly thesis PDF was not readable (HTTP 403); its abstract was read. verify-values run on 2026-11-01, 7 values found in the source text, 12 not checkable by the verifier (their pages were not readable by it; those values were read by hand in this run), 0 not found."
  },
  "sources": {
    "nist-sat": {
      "title": "NIST Chemistry WebBook, water: saturation properties table",
      "id": "NIST SRD 69; CAS 7732-18-5",
      "url": "https://webbook.nist.gov/cgi/fluid.cgi?ID=C7732185&Type=SatT&Digits=5&PLow=&PHigh=&PInc=&T=25&RefState=DEF&TUnit=C&PUnit=MPa&DUnit=kg%2Fm3&HUnit=kJ%2Fkg&WUnit=m%2Fs&VisUnit=uPa*s&STUnit=N%2Fm&Action=Load",
      "year": 2026,
      "kind": "database",
      "license": "US government work (NIST)"
    },
    "nist-webbook": {
      "title": "NIST Chemistry WebBook, water: phase change data",
      "id": "NIST SRD 69; CAS 7732-18-5",
      "url": "https://webbook.nist.gov/cgi/cbook.cgi?ID=C7732185&Units=SI&Mask=4#Thermo-Phase",
      "year": 2026,
      "kind": "database",
      "license": "US government work (NIST)"
    },
    "nist-atomic": {
      "title": "Atomic weights and isotopic compositions: hydrogen and oxygen (NIST)",
      "id": "NIST standard atomic weights",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=H&all=all&ascii=html&isotype=some",
      "year": 2026,
      "kind": "database",
      "license": "US government work (NIST)"
    },
    "pubchem-water": {
      "title": "PubChem compound record: Water (CID 962)",
      "id": "CID 962; CAS 7732-18-5",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Water",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "usgs-water": {
      "title": "USGS Water Science School: How much water is there on Earth?",
      "id": "USGS Water Science School",
      "url": "https://www.usgs.gov/special-topics/water-science-school/science/how-much-water-there-earth",
      "year": 2026,
      "kind": "web",
      "license": "public domain (USGS)"
    },
    "singleterry2013": {
      "title": "Radiation Engineering Analysis of Shielding Materials to Assess Their Ability to Protect Astronauts in Deep Space From Energetic Particle Radiation",
      "id": "NTRS 20140003150; doi:10.1016/j.actaastro.2013.04.013 (Acta Astronautica 91)",
      "url": "https://ntrs.nasa.gov/citations/20140003150",
      "year": 2013,
      "kind": "paper",
      "license": "public domain (NASA)"
    },
    "irwin2025": {
      "title": "Silver Foam: A Novel Approach for Long-Term Passive Dosing of Biocide in Spacecraft Potable Water Systems, Update 2025 (ICES-2025-194)",
      "id": "ICES-2025-194; NTRS 20250005545",
      "url": "https://ntrs.nasa.gov/api/citations/20250005545/downloads/ICES-2025-194.pdf",
      "year": 2025,
      "kind": "paper",
      "license": "public domain (NASA)"
    },
    "muirhead2023": {
      "title": "Evaluation of Iodine and Silver as Biocides for Potable Water in Human Missions beyond Low Earth Orbit (ICES 2023)",
      "id": "NTRS 20220015620",
      "url": "https://ntrs.nasa.gov/api/citations/20220015620/downloads/ICES%202023%20Abstract%20Iodine%20and%20Silver%20for%20Strives.pdf",
      "year": 2023,
      "kind": "paper",
      "license": "public domain (NASA)"
    },
    "gehrke2018": {
      "title": "Utilizing Permanent On-Board Water Storage for Efficient Deep Space Radiation Shielding",
      "id": "Cal Poly master's thesis, 2018 (Nathan Ryan Gehrke); abstract read",
      "url": "https://digitalcommons.calpoly.edu/theses/1933",
      "year": 2018,
      "kind": "paper",
      "license": "thesis (Cal Poly digital commons)"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/water/"
}