With the atmosphere in their little dome now approximating Earth normal, Newt began to wonder if the rest of Sedna's shift was even needed. He  asked her if she was ready to give up her air hair and bird lungs.

She said, "No way. What I'm ready for is to take a walk outside." 

"Outside? Are you serious?"

"Quite serious. I have enough hair now to keep me breathing. Remember, our plants started flourishing when the air in our dome was still thin. The carbon dioxide atmosphere is no danger to me as long as my hair releases enough oxygen."

"But what about the cold?"

"That's why I want to try it now. The outside air is about as warm as it gets. Warmer than an Earth Arctic summer. I think my blubber will be enough."

"But usually it's a lot colder. Way below zero."

"True. Worse than an Arctic winter. But not a lot worse. Polar bears and penguins could stand it."

"Fur or feathers for you, then."

"Fur for sure. Bear can help me with that."

"How much cold will you be able to stand?"

"I won't know until I try it. But I think it was you who pointed out that here on Mars it's not the temperature so much as the heat energy. With thin air the loss of heat by  convection will be limited. Like in a thermos bottle. The only worry is radiation. A reflective coat will handle that."

"Like the silver surfer?"

"More like the abominable snowman. Or Bear. I'll ask him for advice."

So she did. Being brother and sister twins, Bear and Sedna had a very tight Q connection. It took only a moment to open her mind to him. She invited him to join her in the little Mars dome.

Wow Sedna. I didn't know you were doing this.

It's only been a month or so.

Your plants are flourishing!

Plenty of carbon dioxide. And no competition. They're loving it.

I'm loving your new body. When did you do this?

After we got the dome up. So I could work out here. 

And you get oxygen from your hair?

Yup. And I'm planning to go outside.

What if your hair freezes up? What if your whole body starts to freeze up?

That's where I need your help. I'm thinking if I had your polar bear fur I should be okay.

Wow. Shifting on Mars. Becoming a Martian! Leave it to you to think of this. I almost want to be there to try it myself.

It would be great if you were. Meanwhile, can you show me how you do your bear fur?

Might be better to link you to an actual polar bear. Their are subtleties I tend to leave out.

Like what?

Well, for example, the fur isn't actually white. It's translucent, so all incident light gets through to the skin, helping to warm it. And there are two layers. The outer layer is long and stiff. The inner layer is wooly, so it's mostly space. That way any heat given off by the body isn't transmitted through the inner fur, but trapped between the wooly hairs. Also, the skin is black, so it absorbs the light energy that gets in. Beneath the skin there's a layer of fat, with low blood flow. That limits the rate of escape of heat from inside the body. 

I see what you mean. 

She really did see, because this was Q talk, and everything he said was linked to his actual bear familiar, so Sedna got an intimate connection.

Thanks, Bear, she said. After I try it I'll let you know how it goes.

When you're ready let me know, so I can be there with you.

That would be perfect.

Bear returned to whatever he'd been doing, and Sedna turned to Newt. He'd been tuned in, so he knew how it went.

"Wow," he said, "Bear really knows his stuff!"

"That's why we call him Bear."

"It sounds like this could really work for you. Us."

"I'll get started on learning how to make bear hair tonight, after I shift back to normal. Right now, I'm going outside."

Newt no longer wanted to hold her back. But he remained attentive as she went through the air lock.

In the lock chamber, Sedna opened the valve that let the air in the lock slowly equalize to the outside pressure. She took a deep breath, filling her bird lungs with moist, oxygenated air, and opened the outer door. 

Outside, she assessed her body's response to the atmosphere of Mars. She was already attuned to the gravity. The air felt chilly but not uncomfortable on her skin. She turned her attention to her hair. It seemed to relish the nearly pure carbon dioxide atmosphere, soaking it in. She could almost feel it growing. 

The natural Mars air pressure was only about half that inside the dome, but her high-altitude bird-lungs were good for it. She inhaled to draw air into her fresh-air sacs from her moss-like tresses. This also drew fresh air through her lungs into  expanding stale-air sacs. Then exhaling  forced the stale air out while pumping more fresh air into her lungs. Inhaling or exhaling, she was always moving fresh air through her lungs. She felt energized by the oxygen the bird lungs were releasing to her. 

But her exhaled breath became a cloud of fog that dissipated almost instantly, the moisture freezing out of it in tiny crystals. And the bush of green hair that was trying to wrap around and shield her face was rapidly turning white as it metabolized its available moisture.

That ended her experiment. She stepped back into the airlock and closed the outer door. Another breath and she realized it would be her last, unless she could get the inner door open in time. Fortunately her bird lungs sustained her, as the pressure valve let lifegiving air and moisture fill the lock.

Newt was waiting for her wide-eyed, looking almost panic stricken, when she stumbled out of the air lock and into his open arms.

"Your hair!" he said. "What happened?"

 "Spanish moss does great in Louisiana, not so great in Alaska. Watch."

She stepped away from him and shook out her now white hair. As Newt watched she kept shaking it, gently, in the warm moist air of the dome. His panicked look subsided as her hair went from white, to grey, to pale green, and finally to the luminous bright green he had come to love.

 "My hair did great, taking in the carbon dioxide and giving me all the oxygen it could. I've learned to count on that. But it needs water to metabolize the carbon dioxide. It gave me all it had.

"The only thing wrong was that I didn't give it back. It's so cold out there that the moisture I exhaled instantly crystallized. I should have known that would happen. Humidity drops to zero when the air goes below freezing."