Sad days on Mars are just as sad as sad days on Earth, with a caveat: You just travelled 200 million miles to be sad.
Everywhere humans go, our brains (hopefully) go too, so mental health is a thing we have to carefully consider. So it is a reasonable question – on Mars, sMars, and Earth – how do we protect ourselves against mood changes secondary to not getting enough light? AKA: Seasonal Affective Disorder (SAD).
As a physician, I came up against this question from time to time. As a writer, Dignity Healthcare requested that I put together a piece about it, which I hope you enjoy. As the Chief Medical officer on this mission, the question has been put to me: “Are you going to get enough light out there? You don’t want to end up all pasty and depressed, like Finns in the wintertime.”
Fair point! As the CMO, this is my answer. We’ll all be finding out if I’m right….shortly.
1) First, Scandinavians are lovely individuals who happen to live at a high latitude. Also, they are kind of pasty by default. No amount of vitamin D can help that.
2) Second, as I mentioned in my vitamin rant, we have more sources of vitamin D in our lives than just the Sun (which gives pigment cells in our skin a little push. In response, they make vitamin D). Astronauts, coal miners, computer programmers and others who don’t often see the sun do need to make a concerned effort to get enough vitamin D. Conveniently, in this society, many of our foods and drinks are fortified with it. Not so conveniently, there’s much more to saving off SADness than vitamin D.
Well, shoot. Are you saying there’s no silver bullet for SADness?
That’s right. The magic bullet isn’t silver, kids. It’s polychrome. 
What humans need more than anything else to stave off seasonal affective disorder is light. Specifically, full spectrum light – the kind that comes from the Sun, or a special light bulb designed to emit the same colors as the Sun. The Swedes put these bulbs in malls and other public places to keep people from getting depressed during the winter (which improves mood, though not pastiness).
This brings us to the question: how dark does it need to get before I should worry about SAD?
A: That depends on you. For most people, it has to get dark and stay dark for more than a month for the SADness to set in. Some people are sensitive, however. That’s cool. Enjoying the presence of our main sequence supreme energy source on a deeply psychological level is perfectly understandable. If you know that you’re prone to SADness, you should get that full-spectrum light on your face starting in the fall. Keep it coming daily clear through April. Start early – before sun-up – if you want the full effect. Change to a warmer, redder light as it starts to get dark so your brain can start pumping out the sleep hormones and you can get to sleep at a good time.
Noticed that you don’t sleep so great, even though you aren’t depressed? Also, noticed that you stare at screens emitting bright, bluish light all day long while drinking diet coke? Coincidence?
Possibly not. Light should become redder as the day goes on; when it doesn’t, you brain might begin to believe that you need to stay awake. Even though it’s 11 PM, and there’s no more Jon Stewart on the Daily Show (weep).
Programs like Flux will change the color of the light coming out of your screens, which, if you are sensitive to light changes, could help you get to sleep more easily.
Still not tired enough to sleep? Try exercise. 8/10 doctors think that exercise is really, really good for you. The other 2 doctors are too busy performing CPR to add the second “really”.
Q: So, if I decide to do this, I get a full spectrum light, and, like, look at it?
A: Not so much. Please don’t go towards the light, and please don’t stare straight at it.
If you decide to try phototherapy for SAD, let the light fall on your face and head. This is critical for reasons we 
don’t quite understand. The neuroscience-based guess is this: the quality of light gathered by those supremely engineering sensors we call eyes instructs our brains how to behave. In other words, these full-spectrum lights partially fool your brain into thinking it’s a nice summer day. Hence, one does not blast them all the time. 5+ hours of exposure into the face during the winter months is sufficient to help someone with SAD, or to prevent it (maybe).
Now that you understand a bit about sunlight, and its importance to our brains and overall wellbeing, you can see why I keep getting the question – are you all going to get enough light up there? Traditional space missions don’t involve a whole lot of natural light. During our simulated Mars surface mission, we will be going outside during the day, but in suits. For 12 months, we won’t feel the sun, or the rain, or the wind, directly on our faces. Both types of missions boast a lot of bright computer screens.
These are solid arguments for having a few full-spectrum lights on space missions, or maybe any long-term mission. Light therapy staves off depression in some people. It is of little potential harm. You can always turn them on if you need them, or leave them off. If nothing else, sunlight is WAY cheaper than, shall we say, more traditional means of mitigating depression. Alcohol, antidepressants and psychotherapy are all pricer than reproduced sunlight. The lights even look nice.
I’ll miss feeling the sun on my face. It’s one of my favorite things. I don’t think I’ll miss it so much that I’ll get all sad about it. But just in case…I’m bringing a small piece of the Sun along with me.