#Atmosphere, surface temperature and other properties directly related to life
- Magnetosphere:
- Magnetospheres are thought to be driven by a dynamo process driven by internal circulation in the molten core of the planet, are are very useful in protecting the planet from DNA-damaging ionic particles in stellar wind, and helps prevent accelerated atmospheric loss. (eg. Mars)
- Magnetosphere acts like a cut-off filter - stopping cosmic rays below a certain energy, or "vertical cut-off rigidity." It's ~17 GeV at the equator, and <1 GeV at the poles. Cosmic rays are 0.39 mSv/year on surface, but not a lot of shielding happens from the magnetosphere.
- http://www.nasa.gov/centers/langley/science/polar-radiation.html
- http://sol.spacenvironment.net/~nairas/Dose_Rates.html
- Atmosphere:
- Gas retention of a planet is regulated by gravity.
- Composition:
Earth standard http://www.harding.edu/lmurray/113_files/html/d2_earth%20revised/img008.jpg - (at standard pressure/temperature): - Too much Carbon Dioxide: CO2 displaces oxygen. Earth has .0035%, OSHA limits 8hr work day to 5,000 ppm (.5%) - a 30-minute exposure to 50,000 ppm produces intoxication, and concentrations greater than that (7-10%) produce unconsciousness. High concentrations produce acidosis(*). Hypercapnia. Under concentrated conditions, plant roots can actually be suffocated by carbon dioxide. - Too little Carbon Dioxide: Trace amounts (parts per million) regulate blood pH, and perform a few other vital roles. Autoregulation of breathing (but perhaps this is compensated for by generation of CO2 in our lungs?) - Too much oxygen: Oxygen toxicity is a condition resulting from the harmful effects of breathing molecular oxygen (O2) at elevated partial pressures. Hyperoxia. Increased free radicals. Lung damage (inflammation; several days). Fires burn better. At 30%, humans (especially hair and fat) become about as combustible as a paraffin torch. Static electricity = boom. Wet vegetation will burn (at 30%) and lightning/falling rocks/wildfires will take out any available fuel. Other environmental effects; animals, microorganisms, rust, ozone, bleaching, etc. Once you hit the O2 compensation point, plants stop growing. - Too little oxygen: breathing an oxygen deficient atmosphere can have serious and immediate effects, including unconsciousness after only one or two breaths. The exposed person has no warning and cannot sense that the oxygen level is too low. With an atmospheric oxygen level of 11-18%, it results in the reduction of physical and intellectual performance without the sufferer being aware. At 8-11% the possibility of fainting within a few minutes without prior warning. Risk of death below 11%. At 6-8%, fainting occurs after a short time. Resuscitation possible if carried out immediately. At 0-6%, fainting almost immediate. Brain damage, even if rescued. - Too new oxygen: If your oxygen hasn't been around for long enough, it will react with (oxidize) exposed iron and other elements and reduce from the atmosphere. - Too much Xenon: It passes the blood/brain barrier and is used for anesthesia. - Physically Impossible Combinations (i.e. 'Hindenburg' H2 O2 atmospheres) - Physically Improbable Combinations - O2 atmosphere without life (bacteria, most likely). - Low Nitrogen atmosphere (you will need a good excuse to remove/fixate the vast amount of Nitrogen available)
- Too-dense atmosphere
- Earth surface pressure is 100kPa, Venusian pressure (9.2 MPa) is almost 100 times higher (but Venus' mass is lower; 4.868 vs Earth's 5.9736), while Martian pressure (600 Pa) is over 100 times lower. So you need a reason to lose atmosphere.
- Atmosphere loss
- impact-loss (Mars)
- w/o magnetosphere: sputtering, photodissociation (Mars)
- because of magnetosphere: polar wind, charge-exchange
- Jeans escape
- Moon-skimming removes some atmosphere
- Keeping an Atmosphere
- Gravity/size/density
- Ice impact; hydrogen can be removed after dissassociation
- Atmospheric Pressure
- Pressure is too low: At 2,100 m above sea level on Earth, the saturation of oxyhemoglobin begins to plummet - short and long-term adaptations allow humans to go up to about 8,000 m [less than 356 millibars of atmospheric pressure], where no adaptations help (ie: "Death zone"). Sleeping becomes difficult, food digestion impossible with potentially fatal high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE) becoming more common. Humans have survived for two years at 5,950 m [475 millibars of atmospheric pressure], which is the highest recorded permanently tolerable highest altitude; the highest permanent settlement known, La Rinconada, is at 5,100 m. Increased suicide rate (no known cause).
- Armstrong limit: (on Earth ~18,900m) at 6.3 kPa, water boils at 37C: saliva from tongue, tears/water f/eyeballs, water off of alveoli.(*)
- Without supplemental breathing oxygen, the time for useful consciousness at 26,000 ft is 4-6min, at 30,000 ft; 1-2m, and at 38,000 ft; 30sec or less before the aviator succumbed to hypobaric hypoxia. At <1psi unconsciousness occurs at ~14s, length of time it takes for blood to go from lungs to the brain.
- Pressure is too high: Aseptic bone necrosis (long-term). Respiratory acidosis (and ultimately toxicity) (CO2), inert gas narcosis (N2), oxidative stress (O2), High Pressure Nervous Syndrome (HPNS) which occurs beyond 10-15 ATA. Specially trained and equipped (read: very specific, non-natural (helium, non-nitrogen) gas mixes, etc) humans have survived 70 ATA for limited periods of time.
- Radiation
- 5 and 6 Sieverts (Sv) over the course of a few minutes will shred up too many cells for your body to fix at once.
- Even Earth normal background radiation will cause cancer within 4,000 years.
- Surface temperature range:
- Too hot: Hyperthermia. Death after 10m in extremely humid (ie: no sweating) 60C heat.
- Too cold: Hypothermia. Death after core temp reaches 21C - but acclimatization, etc. all impact when this point occurs. Also; special type of hibernation.
- NASA (1958) says indefinite survival at 4-35C / 50% humidity. Somewhat higher temps can be handled if humidity is decreased, and water intake is not limited.
- Core temperature loss is greatly enhanced by wind / sweat evaporation.
- Volatiles: (water) / Must have Water
- Water is required to breathe (alveoli, air exchange). At rest, loss rates from breathing alone range from at least 7-20 ml/h, exercise at 140bpm heartrate is 60–70 ml/h (depending on temperature and humidity). If you're breathing, you will lose water.
- Heat regulation: Sweating occurs when over-heated compared to environmental temperature; humans can sweat when in cold conditions if exercising. If you're working (hunting, farming, most gathering), you will almost always sweat.
- Urination: elimination of bodily wastes uses water. Consistent lack of urination will lead to build up of toxins, liver and other organ failure.
- Must have Food
- Nutrients / Micronutrients (needed from diet: biotin, calcium, choline, chromium, copper, fiber, flavonoids, folate, iodine, iron, magnesium, manganese, omega-3 fatty acids, pantothenic acid, phosphorus, potassium, protein, salt, selenium, vitamin A, vitamin B1 - thiamin, vitamin B12 - cobalamin, vitamin B2 - riboflavin, vitamin B3 - niacin, vitamin B6 - pyridoxine, vitamin C, vitamin D (supplemental), vitamin E, vitamin K, zinc) otherwise various disorders.
- Humans don't produce all the amino acids they need to live.
- Caloric intake varies on lifestyle, age, and gender/size/lean body mass (amongst other factors):
- men: 2,000-2,600 sedentary, 2,200-2,800 moderately active, 2,400-3,000 active.
- women: 1,600-2,000 sedentary, 1,800-2,200 moderately active, 2,000-2,400 active.
