Once I shut everything down, an eerie silence was all that remained. I've spent 449 sols listening to the heaters, vents, and fans. But now it was dead quiet. It's a creepy, eerie kind of quiet that's hard to describe. I've been away from the Hab before, but always in the rover or an EVA suit. There's always some kind of machinery in operation.

But now there was nothing. I never realized how utterly silent Mars is. It's a desert world with practically no atmosphere to convey sound. I could hear my own heartbeat.

Anyway, enough waxing philosophical.

I'm in the rover right now. (That should be obvious, with the Hab main computer offline forever.) I've got 2 full batteries, all systems are go and I've got 45 sols of driving ahead of me.

Schiaparelli or bust!

Chapter 22

LOG ENTRY: SOL 458

Mawrth Vallis! I'm finally here!

Actually, it's not an impressive accomplishment. I've only been traveling 10 sols. But it's a good psychological milestone.

So far, the rover and my ghetto life support are working admirably. At least, as well as can be expected for equipment being used ten times longer than intended.

Today is my second Air Day (the first was 5 sols ago). When I put this scheme together, I figured Air Days would be godawful boring. But now I look forward to them. They're my days off.

On a normal day I get up, fold up the bedroom, stack the solar cells, drive four hours, set up the solar cells, unfurl the bedroom, check all my equipment (especially the rover chassis and wheels), then make a Morse Code status report for NASA if I can find enough nearby rocks.

On an Air Day, I wake up and turn on the Oxygenator. The solar panels are already out from the day before. Everything's ready to go. Then I chill out in the bedroom or rover. I have the whole day to myself. The bedroom gives me enough space that I don't feel cooped up, and the computer has plenty of shitty TV reruns for me to enjoy.

Technically, I entered Mawrth Vallis yesterday. But I only knew that by looking at a map. The entrance to the valley is wide enough that I couldn't see the canyon walls in either direction.

But now I'm definitely in a canyon. And the bottom is nice and flat. Exactly what I was hoping for. It's amazing; this valley wasn't made by a river slowly carving it away. It was made by a mega-flood in a single day. It would have been a hell of a thing to see. 

Weird thought: I'm not in Acidalia Planitia any more. I spent 457 sols there, almost a year and a half, and I'll never go back. I wonder if I'll be nostalgic about that later in life.

If there is a “later in life,” I'll be happy to endure a little nostalgia in return. But for now I just want to go home.

“Welcome back to CNN's Mark Watney Report,” Cathy said to the camera. “We're speaking with our frequent guest, Dr. Venkat Kapoor. Dr. Kapoor, I guess what people want to know is: Is Mark Watney doomed?”

“We hope not,” Venkat responded. “But he's got a real challenge ahead of him.”

“According to your latest satellite data, the dust storm in Arabia Terra isn't abating at all, and will block 80% of the sunlight?”

“That's correct.”

“And can Watney's only source of energy is his solar panels, correct?”

“Yes, that's right.”

“Can his makeshift rover operate at 20% power?”

“We haven't found any way to make that happen, no. His life support alone takes more energy than that.”

“How long until he enters the Tau Event.”

“He's just entered Mawrth Vallis now. At his current rate of travel, he'll be at the edge of the Tau Event on Sol 471. That's 12 days from now.”

“Surely he'll see something is wrong,” Cathy said. “With such low visibility, it won't take long for him to realize his solar cells will have a problem. Couldn't he just turn around at that point?”

“Unfortunately, everything's working against him,” Venkat said. “The edge of the storm isn't a magic line. It's just an area where the dust gets a little more dense. It'll keep getting more and more dense as he travels onward. It'll be really subtle; every day will be slightly darker than the last. Too subtle to notice.”

Venkat sighed. “He'll go hundreds of kilometers, wondering why his solar panel efficiency is going down, before he's notices any visibility problems. And the storm is moving west as he moves east. He'll be too deep in to get out.”

“Are we just watching a tragedy play out?” Cathy asked.

“There's always hope,” Venkat said. “Maybe he'll figure it out faster than we think and turn around in time. Maybe the storm will dissipate unexpectedly. Maybe he'll find a way to keep his life support going on less energy than we thought was possible. Mark Watney is now an expert at surviving on Mars. If anyone can do it, it's him.”

“Twelve days,” Cathy said to the camera. “All of Earth is watching, but powerless to help.”

LOG ENTRY: SOL 462

Another uneventful sol. Tomorrow is an Air Day, so this is kind of my Friday night.

I'm about half-way through Mawrth Vallis now. Just as I'd hoped, the going has been easy. No major elevation changes. Hardly any obstacles. Just smooth sand with rocks smaller than half a meter.

You may be wondering how I navigate. When I went to Pathfinder, I watched Phobos transit the sky to figure out the east-west axis. But Pathfinder was an easy trip compared to this, and I did it mostly with landmarks.

I can't get away with that this time. My “map” (such as it is) consists of satellite images far too low-resolution to be of any use. They just never expected me to be out this far. The only reason I had high-res images of the Pathfinder region is because they were included for landing purposes; in case Martinez had to land way long of our target.

So this time around, I needed a reliable way to fix my position on Mars.

Latitude and Longitude. That's the key. The first is easy. Ancient sailors on Earth figured that one out right away. Earth's 23.5 degree axis points at Polaris. Mars has a tilt of just over 25 degrees, so it's pointed at Deneb.

Making a sextant isn't hard. All you need is a tube to look through, a string, a weight, and something with degree markings. I made it in under an hour.

So I go out every night with a home-made sextant and sight Deneb. It's kind of silly if you think about it. I'm in my space suit on Mars and I'm navigating with 16th century tools. But hey, they work.

Longitude is a different matter. On Earth, the earliest way to work out longitude required them to know the exact time, then compare it to the sun's position in the sky. The hard part for them back then was inventing a clock that would work on a boat (pendulums don't work on boats). All the top scientific minds of the age worked on the problem.