She's boooooooooooooooored. 

This is not, actually, a problem that Merrin is used to having! At all! 

Most dath ilani have a higher need for novelty and cognitive stimulation than Merrin does, and have less stamina. She actually almost never has the "bored but too tired to do anything sufficiently stimulating" problem. And her life is stimulating! She's generally really busy. She's often relieved to spend a rest block aimlessly not doing that much. 

However, "aimlessly doing not that much" actually does usually involve reading (easy) material about topics she finds interesting, or looking at cool pictures, or text-chatting with friends. 

Apparently, actually doing nothing, while fully awake, with an unknown duration of darkness and boredom ahead, and with a lot of problems to solve that feel urgent and don't feel tractable to solve in her head versus by actually working on them, is not at all the same. 

Arghhhhhhh. 

Okay. She'll lie here and mentally plan out exactly how she's going to build a still for seawater desalination out of the materials she has. 

...Merrin gives in to the impatience and briefly turns on the backlight for the oxygen concentrator screen and checks how long it's been running now. 

15 hours, 53 minutes. 

She probably could learn something by looking at the stars for a while, but - long term things. If she sets up something to approximate star-trail photography, or sets up the right equipment to repeatedly measure the exact position of a bunch of stars she can reliably find, she can use that to find celestial north (or south, if she's in the southern hemisphere; she doesn't know yet, she could figure it out by unpacking a compass and checking what side of the sky the sun is on, but she did not do that.)

Anyway. If she knows the celestial pole, she just has to measure how many degrees it is above the horizon and that's - no, is that the latitude or is she getting confused about when she needs to know the axial tilt - no, the axial tilt is actually not relevant to the celestial pole, she doesn't think? It's about the angle of the axis of rotation - the imaginary line drawn between the north and south poles - relative to the sun, but the axis of rotation could exist with or without a sun present at all, it's relative to the other stars...

That's a useful thing to know but it's not worth compromising her already-pretty-questionable shelter's heat retention. 

She'll spend a while thinking about how to set up to do various astronomy measurements that would give her potentially useful data about the planet.

She can turn it into some random mental tangents - her thoughts are getting a bit weird and loopy, with all the lying-in-the-dark - which is fine, she's not trying to think on a deadline, she's just trying to pass the time doing something that isn't totally unproductive. 

....Now how many hours has it been? 

17 hours, 27 minutes. 

Chemistry! She's going to need to rederive as much organic chem as possible from information that exists in her own personal brain plus the reference materials she has with her. The reference materials have stuff that's relevant to, like, pharmacology in the context of a human metabolism, and in general are mostly quite specific to medical purposes, but it's not nothing. 

Can she recall enough of the basics to design experiments that would narrow down the composition of various samples of local plant and animal life, to determine:

1. If digestible calories are present. 

2. If poisonous toxins are present. 

She can determine seawater composition, probably, by literally just using her existing equipment for measuring electrolyte levels in human blood. ...Possibly with a distilled-water dilution protocol and doing calculations from there, she thinks that even seawater on dath ilan would max out those tests on electrolytes like magnesium. And she'll need to read the fine print in her digital reference guide to check if there are weird adjustments to make because blood has plasma proteins and seawater doesn't, from memory she has no idea. (The electronic tablet "book" to read it takes power but not a lot if the backlight is off, she can afford tons of hours of reading with external light sources for every hour of oxygen generation or suit heating.) She also has tests for heavy metal contamination. She should test the seawater, definitely, to know how careful she needs to be about swimming without a suit... 

She cannot think how to test for every possible toxin. There's just a really very large space of molecules that would be toxic to a human metabolism. 

...She can use logic to infer that the intertidal plant life is almost certainly going to be packed full of both antifreeze compounds - and heat-stress-related enzymes, to handle the temperature swings in the other direction - and UV-protective pigments. And, like, on priors weird biomolecules doing specific things like that are more likely to be toxic to her than biomolecules that just store energy or whatnot. 

To find local life that's the least likely to be full of toxins that only might be made safe with enough cooking and processing, she'll need to...go deeper underwater? The molluscs-or-whatever that are always submerged in deep water will be adapted to living in water pretty consistently close to 4° C - the temperature at which water is densest, so on a planet with liquid oceans that never freeze all the way through, the deeper ocean water will tend toward that temperature year-round. 

The tidal situation is going to make it really inconvenient to safely access further down the continental shelf. She....probably wants to do it when the tide is at its highest point, swim down the river along with the current, but if the tidal currents are strong enough she might have trouble getting back to shore until the tide turns, so that's budgeting LIKE SEVENTEEN HOURS of ocean swimming.

She can do it, if her armor is starting out with its battery fully charged, but she doesn't have 17 hours of air supply. She would need to alternate diving and helmet-open treading water at the surface. Which means she should really do it in a week or two when she's acclimatized. (Acclimatizing mostly doesn't mean her lungs will get better at extracting oxygen from the air; her bone marrow will just start producing more red blood cells, so that even a lower hemoglobin saturation still gets adequate oxygen to her tissues, which annoyingly means she can't track acclimatization just off her measured O2 sat readings, and has to figure out what measurements and subjective symptoms to be tracking...) 

It sounds kind of ridiculously dangerous, actually, now that she's thinking through the logistics. A suit electronics failure would straight-up kill her and send her to respawn on ANOTHER random exoplanet because APPARENTLY that's how Reality works

...She has plenty of time to think through the risk-benefit analysis. But she probably has to, sooner or later, or she'll run out of food and die in 45 days. 

What a productive block of thinking-ahead while lying in a sleeping bag in complete darkness! 

...Now how many hours has it been since sunset? 

19 hours, 2 minutes! 

ARGHHHHHHHHH

Merrin is starting to feel like ACTUALLY the greatest hazard of this planet is that at some point she will LITERALLY HAVE A PSYCHOTIC BREAK triggered by SHEER AGONIZING BOREDOM while she's trying to wait out the e n d l e s s night.

Merrin is at this point really, really tired of trying to reason through critical survival-related problems while she feels like she's floating in a causally isolated sensory-deprivation bubble. 

She's just going to lie here replaying the plots of the last eight media series she's consumed over several years in her head. 

NOW HOW MANY HOURS HAS IT BEEN

21 hours 33 minutes!

She's still not freezing in her sleeping bag with the hood up and zipped and only the ventilation slits letting in the ambient air, but when she emerges to check the oxygen concentrator screen, it's now feeling really pretty cold. 

....Temperature sensor check?