....Okay. That could be worse. It would almost certainly settle lower when she's asleep – right now Merrin is trying not to deliberately breathe more than she would otherwise, but that's sort of hard to actually do, and respiratory drive is a little lower during sleep, and her sleeping body would be going off CO2 levels – but she wouldn't die. Probably. 

She still shouldn't sleep without oxygen on her literal first night here. She needs her brain and cardiovascular system functioning optimally.

But humans can and do acclimatize to altitudes with an equivalent partial pressure of O2 to "sea level but with an atmospheric O2 percentage of 13.5%." It takes...about thirty days?...to acclimatize fully, for the average person, but she's fitter than average. 

She turns on oxygen generation at 0.5L/min and waits some more. 

It's already pretty dark in her tent, with the flaps sealed, but it's getting darker, too. The light outside is fading. 

It's too bad Merrin can't walk around outside for a while. On a planet with zero light pollution, the stars - in their alien constellations - are going to be spectacular. 

Astronomy can wait. Merrin has urgent problems to get a handle on first. 

...93%. Eventually, 94%. 

Yeah, that's fine. If she can manage to sleep without dislodging the pulse ox, it'll start alarming if she goes below 90%, but even if it didn't, she's not going to die of hypoxia in her sleep. Not even if she dislodges the nasal cannula, she would just wake up a bit stupid but she almost certainly wouldn't have given herself permanent brain damage from a night of sleeping with her sats in the high 80s.

Merrin has been awake for well over 24 hours now and is really very ready to finally get some sleep. 

...She makes herself eat a meal bar first. In the dark, by feel. 

(1200 calories, and it has all of the key nutrients - essential amino acids, essential fats, vitamins, minerals, etc - that she would need per day. In theory, if she can find anything on this planet that contains human-digestible calories at all, she could top up the rest of her diet with that and get it down to one bar a day rather than the three her stores budget for. ...Three in a 24 hour day, that is, and her supply would last 45 days on dath ilan, not that she's ever had a real or simulated wilderness scenario last anywhere close to that long, normally the extended food crate is the one she would ditch first because 15 days is already a long time for any of her sims, but she's very glad that Exception Handling overprepared her, here.) 

...Water. She needs to figure out water. She's consumed 80% of what's in the 3L drinking bladder in her suit, with all the activity today, she wasn't rationing herself at all. (Note to self she also needs to CLEAN THE RESERVOIR she put meal replacement powder in it.) 

She has another 5L. That's enough for 48 hours, unless she rations it and dehydrates herself a bit. Two days, on dath ilan. But, in fact, she needs to solve her water problem tomorrow, because the days on this stupid planet are at least 60 hours long. 

And she's not prepared for a lost-at-sea training scenario, for which they would have given her a desalination kit of one form or another. She can purify fresh water, but she has no idea how far she would have to go to find reliably fresh water. She'll need to build a still.

Fortunately, guess what she has a whole bunch of: various tubing for medical purposes! And lots of plastic, and ways to make a seal. And this planet has no shortage of daytime heat to evaporate seawater by. She just needs to make sure she actually handles that early in the day, because if she has another active day she'll drink most of her water before it's even nightfall.

...Actually, Merrin is very silly, isn't she. She didn't unpack any of her water, because she had not thought through the fact that she's not going to just sleep through a "night" that could be two dath ilan days long. She knows exactly where it is, outside the tent, in the main provisions box, but now it's completely dark outside...

- stars, hopefully? Clear sky? And she's night-vision-acclimated. She'll just need to breathe ambient air for five minutes, since she didn't prep for mobile O2 and it's not worth putting her suit back on and power-cycling it, its systems are entirely switched off right now and booting up the power takes more than just keeping it running. 

The stars are very bright - at least, to Merrin's darkness-acclimated eyes - and very beautiful, and there are no recognizable constellations at all. 

(They do not actually shed much useful light - she can't super see her own feet - but she can see the shadow of the tent against the horizon, and pick her way around it.) 

...If Merrin has to be in the situation of having DIED IN A PLANE CRASH - that should not have happened in the first place because the base rate of that happening is really actually very low - and then had this inexplicably result in being STRANDED ON AN EXOPLANET that seems to WANT TO KILL HER - well, the planet itself is obviously not sapient and cannot have intentions unless Reality here works really very differently than her model of Reality in dath ilan, but it sure feels like the situation has been optimized for deadliness by some kind of agent - 

- anyway. If she has to be in this situation which she hates. She is at least going to enjoy the small upside of staring at alien stars. 

...For thirty seconds. It's getting cold out here. And she's not breathing enough oxygen and shouldn't let that continue longer than necessary.

She knows exactly where she put all of the crates, and which one is primary provisions, and how its contents are arranged. It takes her two minutes to retrieve two liters of water, properly seal the box again - what if there's a dust storm? or a normal storm? - and carry them into the tent. 

- actually, you know what, first she's going to set them down right outside the closed flap and go walk ten meters away and pee. She has the camping-supply-pouch on the inside of the tent tarp and it includes a collapsible bucket but she should save the bucket capacity for later in the night. 

Arghhh there might be a rainstorm and in that case she would really want to have caught some of the rain but she. Does not, actually, have the energy to go unpack any more gear and rig up a rain-collection cistern. Whatever. She'll sleep, and wake up, and it'll still be night, and if she hears rain she can put on her armor and go out in it and do it then. The extra power usage would be worth it, for water. ...Scratch that, nighttime precipitation will almost certainly come down as snow, she'll...figure something out...if she emerges in the morning and finds a lot of pristine snow that she might be able to collect before the day warms up and it melts...

Merrin's thoughts are getting pretty loopy, and it's probably not lack of oxygen - back in the tent, her sats are only down to 90% at the point when she restores the pulse ox to her finger and switches the oxygen concentrator back from standby to lowest-rate generation, she was probably subconsciously overbreathing a little bit - it's just. That she's been awake and active for way too long. 

She manages to get at the drinking tube via the helmet of her armor suit and drink everything else in there. It'll get gross if she leaves it. 

And then she unpacks the sleeping back from its pouch, shakes it to re-expand the insulation lining fully - it packs down small - and wriggles in, and lies down. 

She's asleep in under a minute. 

When Merrin wakes up, the temperature in the tent is definitely around the freezing point. She can tell because she drooled a tiny bit in her sleep, and now it's frozen. 

Ugh. 

...What time is it. Or, rather, how long has it been. She's going to want to figure out how to reprogram her dath ilan-manufactured wrist timepiece for a longer day. She turns on the backlight to read it, realizes that she did not actually fully consciously register the time-in-dath-ilan last time she looked at it, and goes to instead switch the backlit oxygen concentrator screen back on and see how long it's been running. 

(Merrin is not, in fact, particularly disoriented about where she is at the moment of waking. Last night was very memorable, and she's pretty good at orienting instantly on waking if she...the best way to put it is "knows she's in a high stakes emergency or a training for one" and yesterday wasn't not something that smells like an Exception Handling training. It was, in some ways, not even that weird a day for Merrin. The part that takes her longer to fully reorient to, and hits her with an almost physical-feeling force, is the part where she DIED IN A PLANE CRASH and apparently the result of True Death was not in any way what she had expected and now she's here.) 

It's been 13 hours. 

The camping-gear-pouch has a temperature sensor in it. Small, low power use, non-rechargeable internal battery, runs for ten (dath ilan) days once switched on. (She has a few extra in the tools-and-power crate.) 

Merrin finds it by feel and switches it on and holds it up realllly close to the backlit oxygen concentrator screen, because the sensor itself is not wasting any power on things like a backlit screen readable in near-complete darkness. 

It's -2° C inside the tent. 

The cold isn't actually what woke her. The parts of her body inside the sleeping bag are perfectly cozy. She mostly woke up due to having slept as much as she needed even with her exhaustion going into it, and due to REALLY NEEDING TO PEE.

...Collapsible bucket next. It'll probably freeze solid by morning, won't it. At least that will mean slightly less of a disaster if she's dumb and knocks it over by mistake. 

Urgent bodily functions dealt with and a major source of distraction removed: ...what are her sats on the pulse ox? What's the trendline like?

She doesn't have the rest of her basic field monitoring suite set up, which includes both an actual small display screen and controls and also a computer that can store - well, she's never run out of memory for medical data - so she has to use the built-in menu navigation side button on the pulse ox, and she only has the what it can store in its built-in memory chip, which she had apparently last set to every-five-minutes point readings but at least she has them for the whole 13 hour period she was asleep. 

Her lowest reading was 89%, and it's a single reading with 91% on either side, it might have been sensor error. The average was around 92% and a few times it went as high as 95%. 

She in fact feels fine, cognitively speaking. Well, except for the part where sitting in near-complete darkness is making her feel less than fully awake, but she thinks her metacognition and mental math abilities and all that are working fine. Physically, she's pretty sore – she did almost twenty-four hours straight of physical labor, with the bare minimum power assist from the armor so she could stretch its battery life. 

She is incredibly ravenously hungry, which is very unsurprising, she has to be running a massive calorie deficit from yesterday.

Food is...going to be a problem...but not in the near-term. It's prooobably worth it to eat as much as her appetite wants during the initial few days when she's still figuring everything out on the fly and really can't afford to be mentally-low-energy. 

The dense chewy nonperishable complete-nutrition bar she eats is possibly the most delicious thing she has ever eaten in her entire life. 

After eating a bar slowly and drinking a lot of water and waiting a while, she's still ravenously hungry. She'll eat a second one. 

...Now how long as it been since about-sunset? 

13 hours 40 minutes!

...She should check the outside temperature. For information value. 

Merrin manages to unseal a tiny strip of tent flap, and hangs the temperature sensor out on a bit of cord. (She has eighteen different lengths, thicknesses, and stretchinesses of Small Rope in the camping-gear pouch.) 

It's about -16° C outside. 

...Well, at least that's some reason to think her insulation is effective, and will hopefully continue to be effective and keep the indoor temperature more than 10° C above the outdoor temperature? 

It's already cold enough that being even partially out of the sleeping bag is uncomfortable, and there's no reason to. There's not, actually, much that Merrin can productively do, except lie here and not die of hypothermia. 

(She should turn off the pulse ox entirely, actually, now that she's awake and she knows the reading was stable when she was asleep. Operating independently on only its internal battery, it'll last for 24 hours of continuous use, but she's already spent almost 14 of those hours and she's in "use as little electricity as possible" mode right now.) 

She stows it in a zipped tarp pocket where it won't get lost, and then wriggles fully into her sleeping bag again and lies down.