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The Maretian

by Kris Overstreet

Chapter 210: Sol 383

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“Randall,” Venkat asked, “what’s going on with Mars’s weather? I thought you said the dust was coming back. Watney tells me the sky’s still as blue as the first Viking photos- and those were a color balance screw-up.”

“Clouds,” Randall Carter replied. He handed Venkat printouts of some satellite photos from Mars’s more distant orbiters. “Normally we get a lot of cirrus clouds- high-level clouds made of tiny water ice crystals- this time of year, when Mars is farthest from the sun. Technically the time for that was a couple months ago, but they’re back, and they’re growing.”

“What’s causing it?” Venkat asked. “Nucleation around dust particles?”

“That’s a possible cause,” Carter agreed cautiously. “But more to the point, the higher than normal temperatures in the zone between the equator and latitude 30 have probably caused a lot of water ice just under the surface to sublimate and enter the atmosphere. More water in the atmosphere means more clouds. And every time a water crystal forms in the air, it traps the dust particles it uses for nucleation points, effectively clearing the sky.” He tapped a photo of the edge of Mars’s planetary disc, clearly showing the bright blue band of its upper atmosphere. “And without the dust in the air, you're left with ordinary gas molecules and the same Rayleigh scattering effects we see on Earth. So that’s what Watney sees- blue skies.”

“All right, sounds pretty harmless,” Venkat said. “How long will it persist?”

“My guess is, roughly a month,” Carter said. “Maybe less. As Mars gets closer to the sun again, those cirrus clouds tend to sublimate again. The water vapor either gets broken up by UV rays into oxygen and hydrogen that escape the atmosphere or else gets circulated to a lower layer of air and condenses back onto the surface.” He pulled out one more bit of paper and added, “The thing is, I don’t think this trend is harmless.”

Venkat looked at the paper. “Randall, I’m a physicist, not a meteorologist,” he said. “I see these temperature and air pressure readings, but I haven’t got a background to interpret them.”

“They’re too high,” Randall said. “This is northern summer on Mars, and Mars is just beginning to swing back in towards the sun. Right now carbon dioxide should be freezing out of the air in the southern hemisphere, causing air pressure to drop. It’s not.”

“Why not?”

“Too hot. At Mars’s normal atmospheric pressure, carbon dioxide condenses at about negative 123 degrees Celsius,” Randall said. “Normal peak lows in southern winter hit or surpass minus 150. We can see it happening in seasonal photos as the ice cap expands and contracts each Martian year. The growth and shrinkage is almost all CO2. But right now temps at the poles are only dipping below the freeze point for brief periods of time, and not in a very large area. So Mars’s atmosphere is staying put.”

“Fine,” Venkat said. “But I’m not seeing how that affects Watney and the ponies.”

“I don’t see how it does either,” Randall said. “But I’m sure it will affect them. As it is, the thicker atmosphere than normal plus the cloud coverage- did I mention it’s growing? Mark will see the clouds before much longer. Anyway, water vapor is a greenhouse gas, though not in the league of CO2 or methane. The daytime heating isn’t going to dissipate as rapidly at night. Mars is about to experience the closest thing it ever gets to a heat wave.”

“How hot are we talking about?” Venkat asked.

“Double-digit positive Celsius highs at the Hab for the next two weeks at least,” Randall said. “Still about minus forty at night, but during the day the atmospheric regulator external component is going to shut down due to excessive heat. It requires super-cold temperatures to help condense components of the atmosphere-“

“Yes, I know how it works, I’m not that uninformed,” Venkat grumbled. “But the internal portion will still function, as will the oxygenator.”

“I’m not too worried about the Hab equipment,” Randall said. “I’m worried about what will be the next weather pattern after this one. This is weather we’ve never seen on Mars before, and it’s damn near global. Global temperatures twenty degrees Celsius higher than normal, day and night. That’s a lot of energy being stored up in the atmosphere. It has to go somewhere.”

“Try to figure out where,” Venkat asked.

“I already have one guess,” Randall said. “But you’re not going to like it.”

“I like it better than no guess at all. Give.”

“All right. Higher temperatures on Earth mean more giant storms- hurricanes, typhoons nor’easters, the big weather systems. They work as a means of transferring heat energy from the ground and lower atmosphere into the upper atmosphere, where it can radiate away into space. Mars doesn’t have rainfall. The closest it comes to precipitation is the occasional dry-ice snowfall at the poles. So it has only one way to do the same thing: planetary dust storms.”

“When?” Venkat asked. “This is urgent, Randall. We’re about to send six people on a perilous journey across thousands of kilometers on solar power. And for reasons of logistics, we can’t send them immediately. I need answers.”

“I’ll try to get them, Dr. Kapoor,” Randall said. “But right now we’re all guessing. We’ve got no baseline to use for predictions, not with this.”



“That’s the deal, is it?” Teddy asked.

“That’s it,” Venkat said. “I’ve thought about putting some people to work on a crash program to get the castaways on the road now, but I recommend against it.”

“Give me the pros and cons.” Teddy unconsciously straightened papers on his desk that were already perfectly aligned with the blotter.

“Okay. Pro: the sooner they roll out, the more leeway they have to make Schiaparelli by Sol 551. Up to a point the time pressure is reduced. But that’s the only pro. Con: more food would have to be packed into a vehicle that’s already critically overweight. In case of a global dust storm like, for example, the 2018 event, we’d rather have them at the Hab missing the Hermes flight than somewhere in the middle of Arabia Terra. The Hab and the cave are more durable, should the global storm include wind events like the Sol 6 storm or electrical outbursts like the Sol 247 storm.”

“So, we keep them in Acidalia if we see a dust storm forming on Sol 451?” Teddy asked.

“Not necessarily,” Venkat replied. “Remember, we knew going into this that the drive to Schiaparelli would take place at the beginning of dust storm season on Mars. There was already a minor risk of being stranded by a dust storm, but it was just that: minor. Blackout global dust storms are almost a once-a-generation thing. There are some Martian years that don’t even have a global dust storm, not even a thin one. But even so, the risks of the trip just aren’t lowered enough by an early departure to offset the logistical difficulties.”

“All right,” Teddy said. “I’ll leave this to your discretion, Venk, but please contact me if the meteorology staff comes up with anything more definitive.”

“You’ll be the seventh to know,” Venkat said solemnly.

Author's Notes:

The color of the Martian sky, surprisingly, is extremely controversial, and not just thanks to Cydonia-face, fake-Moon-landing conspiracy nuts.

The fact is that the Viking lander cameras, those who sent us those first photos of Mars with a brilliant blue sky, didn't have proper color calibration. Subsequent Mars landers from Pathfinder on included a color chit on their bodies somewhere the cameras could reach that would allow for proper calibration. (It doesn't help matters that NASA releases color-enhanced or altered photos to the public. Yes, the color changes are there for good reasons, but they're not the SAME good reasons.)

And yet, there are a few shots which suggest an occasional blueness to Martian air- photos taken from orbit of the edge of the atmosphere, shots pointing almost straight up rather than at the horizon, and shots of haze-free days.

As Randall Carter explains, what gives Mars air its reddish tinge is the same dust layer that covers the planet. Sweep away that dust, and Mars rocks are grey, and Mars sky is... just possibly... blue. We won't know for certain, of course, until humans go there and spend quite some time on the surface looking up. No digital camera is a perfect imitation of the Mk. 1 eyeball.

Sales today were ROTTEN at Mechacon. Wishing I was at Bronycon. Or, for that matter, practically any other con at all.

Next Chapter: Sol 387 Estimated time remaining: 8 Hours, 39 Minutes
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