Thanks to the low pressure of the Martian atmosphere, the dirigible is the chosen mode of flight and is significantly less dangerous.
The two travel around Mars, occasionally dropping anchor and setting a windmill down. The small heating coils on their machines won't do much to heat the planet, but as Arkady points out, even a little bit is a start.
They also discuss some of Sax's ideas for terraforming, like dropping meteorites from Saturn to introduce hydrogen and oxygen into the atmospheric mix. Not his best idea, but thankfully not his only idea.
As they travel, they realize why people say the decidedly smaller Mars has "as much land surface as the Earth" (2.7.36). Its mountains are huge.
Days pass, and wouldn't you know it, they hook up.
Nadia wonders why her of all people, and Arkady answers it's because her beauty includes more than her curves—though the curves are still a plus.
One morning, they go to set a windmill but the winch hook messes up and drops it. Nadia descends to check things out, only to find a glob of GEM algae within the thing.
She calls for Arkady to pull her up and confronts her new lover—but Arkady's in the dark as much as she is on the matter (though he is also slightly more amused).
They check other windmills and find secret panels filled with the algae.
Since Arkady was in the dark, this means there was a group working in Underhill subverting both UNOMA and Arkady. How's that for some plot thickener?
They guess Sax is involved. And Vlad. Hiroko, well, she's as enigmatic as ever, though whoever is responsible probably got her permission.
No time for conspiracies, though. John Boone jumps on the phone to let them know sandstorm season has come early this year.
Not a big deal, right? They can just fly back. Well, minus the little point that their dirigible runs on solar power. And dust storms mean no sun. No sun, no power—and no power makes for some very weaksauce indeed.
The night of the storm wears on as they take turns at the helm while the other one sleeps.
Nadia has the idea that they can collect the sun reflecting off the ground for a slow, but necessary, battery recharge.
Nadia preps, and they bring the dirigible close to the ground for the low winds.
Nadia is out and going to work. At one point, the winds bring the dirigible down and Nadia drops to the ground, almost crushed in the process.
She returns to the ship and the hours pass until darkness. When Nadia is making her meal, she gets an idea: if they can make it to one of the transponders they set on their way to the North Pole, they can anchor the dirigible and drive back home on one of the robotic vehicles.
They set the plan in motion. Three days pass. They need to use radio ping to land the flying beast, but when Nadia gets out, she manages to find the transponder despite the low visibility and high winds.
On the way back to Underhill, they hear that UNOMA approved the establishment of follow-up colonies and a bunch of terraforming efforts.
Arkady laughs. Whoever put the algae on those windmills is going to get away with it.