{"group":"survive","pic":"living/pics/air-city.webp","question":"How do you breathe on a planet with almost no oxygen?","answer":"You make your own air. Machines split water into oxygen and scrub every room clean, so the helmet comes off the moment you step inside.","play":{"label":"Walk through an airlock","href":"play/?at=0,-60,0,0.18,14&era=city&light=day"},"breath":{"title":"One breath of air","line":"Fill your lungs on each world and count what is in them.","earth":"Earth","mars":"Mars","big_earth":"1,000","big_mars":"{a_mols}","unit":"molecules, for every 1,000 in a breath on Earth","parts":{"co2":"Carbon dioxide","n2":"Nitrogen","ar":"Argon","o2":"Oxygen","other":"Argon and others"},"safe":"Under every dome and down every row, you breathe the city's own air instead."},"steps_title":"Inside the air plant","steps":[{"icon":"split","title":"Split water","text":"Electricity splits water into hydrogen and oxygen in tall cells, like the space station's oxygen maker."},{"icon":"scrub","title":"Scrub the air","text":"The carbon dioxide you breathe out is trapped in beds of a mineral sponge, then pushed outside into air that is already {mars_co2}% carbon dioxide."},{"icon":"tank","title":"A month in reserve","text":"Liquid oxygen waits in tanks beside the homes: {reserve_days} days of breathing for everyone."},{"icon":"mix","title":"The perfect mix","text":"Blended with nitrogen and argon from Mars's own air, it reaches every room at {cabin_kpa} kPa with {o2_pct}% oxygen."}],"o2":{"title":"Oxygen in every breath","sub":"Each column is the air pressing on you, drawn to scale. Green is its oxygen.","earth":"Earth, seaside","town":"Arcadia, indoors","mars":"Mars, outside","kpa":"kPa","line":"Less air presses on you than at home, but more of it is oxygen. Each breath carries {a_o2_share}% of the oxygen of a breath at the seaside."},"day":{"title":"A day of breathing","sub":"What one person needs, drawn to scale by weight.","water":"{a_water_day} kg of water","o2":"{a_o2_day} kg of oxygen","h2":"Hydrogen, to the fuel plant","co2":"{co2_day} kg of carbon dioxide out","line":"About {a_water_day} litre of water a day, roughly {a_bottles} bottles, becomes all the oxygen you breathe. The carbon dioxide you breathe out is pulled from the air long before it reaches {co2_target} mmHg, under the level that gives space crews headaches."},"earth_mars":{"earth":{"head":"Air you breathe without thinking"},"mars":{"head":"Air with almost no oxygen"},"pics":{"earth":"living/pics/em-air-earth.webp","mars":"living/pics/em-air-mars.webp"},"rows":[{"label":"How thick","icon":"air","earth":"{earth_kpa} kPa of air presses on you at the seaside.","mars":"Only {air_pct}% as thick as Earth's."},{"label":"Oxygen","icon":"leaf","earth":"{earth_o2}% of every breath is oxygen.","mars":"{mars_o2}% oxygen, and {mars_co2}% carbon dioxide."}]},"living":"The air in every room is made from water and kept just right: a little thinner than at home, a little richer in oxygen, and always fresh. Helmets come off at the inner door, and you breathe as easily as you do by the sea.","fact":"On Mars itself, from 2021 to 2023, a machine called MOXIE made {moxie_g} g of oxygen out of the thin Martian air in {moxie_runs} runs, at up to {moxie_gph} g an hour.","card":"air","pin":[0.74,0.28],"scene":{"pic":"living/pics/scene-air.webp","look":"03-09","shot":"hall","focus":"50% 50%","lap":100,"spots":[{"at":[0.2,0.4]},{"at":[0.5,0.6]},{"at":[0.7,0.58]},{"at":[0.6,0.12]}]},"proof":{"pic":"living/people/air-proof.webp","place":"Being fitted into Perseverance, California","when":"On Mars from 2021 to 2023","head":"Oxygen made on Mars","credit":"Photo: NASA (public domain)"},"quiz":[{"q":"How much of Mars's air is oxygen?","a":["{mars_o2}%","About a fifth, like Earth's","{mars_co2}%"],"why":"Mars air is {mars_co2}% carbon dioxide and only {mars_o2}% oxygen, and just {air_pct}% as thick as Earth's.","more":"In Biosphere 2, oxygen fell from {b2_start}% to {b2_low}% in {b2_months} months as soil microbes used more than the plants made. Arcadia's machines carry the whole load, never the plants alone.","cite":"02-01 F-06, 03-09 F-24, LS-08","from":"problem","fig":0,"icon":"air"},{"q":"Where does the oxygen you breathe in Arcadia come from?","a":["Water, split by electricity","The farms' plants alone","Tanks shipped from Earth"],"why":"Electricity splits water into hydrogen and oxygen in the air plant's tall cells. The farms only help.","more":"The space station's oxygen maker splits water the same way. It can make up to {oga_max} kg of oxygen a day and has run since {oga_since}.","cite":"03-09 F-14, LS-04","from":"fix","fig":0,"icon":"drop"},{"q":"About how much water becomes one person's oxygen each day?","a":["About {a_water_day} litre","About a bathtub","A teaspoon"],"why":"About {a_water_day} litre a day, roughly {a_bottles} bottles, splits into the {a_o2_day} kg of oxygen one person breathes.","more":"In Krasnoyarsk, BIOS-3 kept {b3_crew} people sealed inside for {b3_days} days in {b3_y1} to {b3_y2}, with tanks of algae and crops helping to make their air.","cite":"03-09 F-09, F-23","from":"why","fig":1,"icon":"drop"}],"notes":[{"beat":"fix","text":"Every home has at least two carbon dioxide removers, either able to do the whole job alone.","cite":"03-09 LS-05"}],"from":"From the air plant","everyday":{"title":"A day of fresh air","items":[{"time":"06:30","head":"Helmet off, deep breath","text":"Back through the airlock after a dawn walk, the helmet comes off and the first breath indoors is cool and fresh.","tag":"{o2_pct}% oxygen","pic":"living/pics/air-city.webp","pos":"50% 50%"},{"time":"12:20","head":"Your breath feeds the farms","text":"The carbon dioxide you breathe out is caught and piped away, some of it to the farms, where crops grow faster on it.","tag":"{co2_day} kg a day each","pic":"living/pics/food-city.webp","pos":"45% 55%"},{"time":"21:00","head":"A month asleep in the tanks","text":"Liquid oxygen rests in tanks beside the homes, enough for everyone to breathe for a month and more.","tag":"{reserve_days} days spare","pic":"living/pics/scene-air.webp","pos":"75% 70%"}]}}