{"group":"place","pic":"living/pics/dangers-city.webp","question":"What does Mars throw at the people who live here?","answer":"Four things: air too thin to breathe, deep cold, radiation from space and fine, salty dust. The city beats every one, so inside, life is warm, safe and easy.","play":{"label":"Check the radiation meter","href":"play/?era=city&light=day"},"four":{"title":"The four dangers, up close","line":"What a suit and a home are built to beat.","items":[{"id":"air","name":"Thin air","big":"{air_pct}%","unit":"as thick as Earth's","text":"Below {arm_kpa} kPa, water in the body boils. Mars's air is about {arm_x} times thinner than that."},{"id":"cold","name":"Cold","big":"{mars_c}°C","unit":"on average","text":"On the equator at noon your feet would feel spring at {t_feet}°C and your head winter at {t_head}°C."},{"id":"rad","name":"Radiation","big":"{h_plain_xray}","unit":"chest X-rays a day","text":"With no magnetic field and thin air, radiation from space reaches the open plain."},{"id":"dust","name":"Dust","big":"{dust_d} µm","unit":"grains","text":"Charged grains cling to suits, tools and seals, and the soil carries salts that harm people."}]},"beats_title":"How Arcadia beats all four","beaten":[{"icon":"house","name":"Air: a sealed shell","text":"Every home is a steel shell that holds its own air at {cabin_kpa} kPa, soft and easy to breathe."},{"icon":"layers","name":"Radiation: {cover} m of soil","text":"A thick blanket of soil over every home stops most of the radiation from space."},{"icon":"thermo","name":"Cold: warmth kept in","text":"The soil holds the warmth in so well, and the thin air takes so little away, that radiators shed the spare heat."},{"icon":"helmet","name":"Dust: cleaned at the door","text":"On the porch, brushes, air blasts and electric dust shields strip every suit before the lock opens."}],"press":{"title":"Where the air runs out","line":"Air pressure on one ladder, each step ten times the one below.","earth":"Earth at sea level","home":"Your home","suit":"Inside a suit","boil":"Blood would boil below here","mars":"The Martian air","text":"Homes and suits keep everyone well above the line where body water boils. Out on the plain the air sits about {arm_x} times below it."},"heat":{"title":"Cold, but slow","line":"Where a suited person's warmth goes, out on the plain.","boots":"Into the ground","sky":"Glowing to the sky","air":"Into the air: very little","text":"Air this thin carries away almost no heat. A suit loses its warmth through the boots and by glowing to the sky, so even at {mars_c}°C the cold comes on slowly."},"earth_mars":{"earth":{"head":"The air looks after you"},"mars":{"head":"The city looks after you"},"pics":{"earth":"living/pics/em-dangers-earth.webp","mars":"living/pics/em-dangers-mars.webp"},"rows":[{"label":"Air","icon":"air","earth":"Thick air, about {earth_o2}% oxygen.","mars":"Only {air_pct}% as thick as Earth's, and {mars_co2}% carbon dioxide."},{"label":"Cold","icon":"thermo","earth":"About {earth_c}°C on average.","mars":"About {mars_c}°C on average."},{"label":"Radiation","icon":"rad","earth":"About {earth_bg} mSv a year of natural background.","mars":"About {h_plain_y} mSv a year on the open plain."},{"label":"Dust","icon":"layers","earth":"Dust you wipe off and forget.","mars":"Grains about {dust_d} µm across that cling to everything."}]},"living":"Inside, you never think about the four dangers at all. The air is soft and warm, the radiation stays outside under {cover} m of soil, and the dust is brushed off at the door. Going out is an adventure you suit up for, always with a friend.","fact":"Mars's wind cleans as well as it dirties. In March 2014 gusts swept the dust off Opportunity's solar panels: by mid-April they made over {opp_hi} watt-hours a day, against under {opp_lo} in January.","later":{"pics":{"city":"living/pics/dangers-city.webp","far":"living/pics/dangers-far.webp"},"city":{"tag":"Suit up to go out","text":"Outside, everyone wears a suit and works in pairs. Inside, soil, steel and airlocks keep all four dangers out."},"far":{"tag":"Slim suits, open streets","text":"Slim, close-fitting suits for the plain, and under the domes' water roofs, everyday clothes all day long."}},"pin":[0.645,0.52],"scene":{"pic":"living/pics/scene-dangers.webp","look":"02-01","shot":"way_in_cut","focus":"40% 50%","spots":[{"at":[0.12,0.62]},{"at":[0.2,0.12]},{"at":[0.65,0.42]},{"at":[0.41,0.5]}]},"proof":{"pic":"living/people/dangers-proof.webp","place":"Meridiani Planum, Mars","when":"March 2014","head":"Wiped clean by the wind","credit":"Photo: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ. (public domain)"},"quiz":[{"q":"How does a home beat the thin air?","a":["It holds its own air inside a sealed steel shell","The soil on top holds the air in","People get used to thin air"],"why":"Every home is a sealed steel shell. The soil on top is a blanket against radiation and cold, never a lid holding the air in.","more":"NASA's space station suit holds {emu_kpa} kPa of pure oxygen, less than half the pressure of a home here.","cite":"03-06 HA-02, 03-08 F-02","from":"fix","fig":0,"icon":"house"},{"q":"Where does a suit lose most of its heat outside?","a":["Through the boots and by glowing to the sky","Into the thin air","Through the helmet"],"why":"Air this thin carries away almost no heat, so warmth leaves through the boots and by radiating to the sky.","more":"Near the poles, the coldest Martian nights fall to about {t_low}°C.","cite":"02-01 S-16, F-21","from":"why","fig":1,"icon":"thermo"},{"q":"Where does the dust come off?","a":["On the porch, before the lock opens","In the living room","It stays on the suit"],"why":"Brushes, a floor grille, electric dust shields and a blow-off of compressed Mars air strip every suit on the porch.","more":"In {eds_year} NASA's electric dust shield worked on the Moon, lifting {eds_glass}% of the dust off glass with no moving parts at all.","cite":"03-07 AD-04, F-29","from":"fix","fig":0,"icon":"layers"}],"notes":[{"beat":"fix","text":"Air pressure steps down from the clean rooms to the suit room, so air always flows towards the dust and never into the home.","cite":"03-07 AD-05"}],"from":"From the airlock porch","everyday":{"title":"A safe day","items":[{"time":"08:00","head":"Suit check","text":"Before a shift on the plain you and your partner check each other's suits, helmet to boots.","tag":"Always in pairs","pic":"living/pics/dangers-city.webp","pos":"40% 50%"},{"time":"13:00","head":"Brushed clean at the door","text":"Coming back in, air blasts and brushes strip the red dust off on the porch before the lock even opens.","tag":"{clean_min} min on the porch","pic":"living/pics/scene-dangers.webp","pos":"41% 45%"},{"time":"19:00","head":"Warm and safe at home","text":"Dinner under {cover} m of soil: the radiation stays outside and the air is soft and warm.","tag":"{h_rows_x} times less radiation","pic":"living/pics/scene-dangers.webp","pos":"10% 65%"}]}}