Want to know what elevation zero means? On Earth, it’s sea level. Obviously, that won’t work on Mars. So lab-coated geeks got together and decided Mars’s elevation zero is wherever the air pressure is 610.5 pascals. That’s about 500 meters up from where I am right now.

Now things get tricky. Back in Acidalia Planitia, if I got off course, I could just point in the right direction based on new data. Later, in Mawrth Vallis, it was impossible to screw up. I just had to follow the canyon.

Now I’m in a rougher neighborhood. The kind of neighborhood where you keep your rover doors locked and never come to a complete stop at intersections. Well, not really, but it’s bad to get off course here.

Arabia Terra has large, brutal craters that I have to drive around. If I navigate poorly, I’ll end up at the edge of one. I can’t just drive down one side and up the other. Rising in elevation costs a ton of energy. On flat ground, I can make 90 kilometers per day. On a steep slope, I’d be lucky to get 40 kilometers. Plus, driving on a slope is dangerous. One mistake and I could roll the rover. I don’t even want to think about that.

Yes, I’ll eventually have to drive down into Schiaparelli. No way around that. I’ll have to be really careful.

Anyway, if I end up at the edge of a crater, I’ll have to backtrack to somewhere useful. And it’s a damn maze of craters out here. I’ll have to be on my guard, observant at all times. I’ll need to navigate with landmarks as well as latitude and longitude.

My first challenge is to pass between the craters Rutherford and Trouvelot. It shouldn’t be too hard. They’re 100 kilometers apart. Even I can’t fuck that up, right?

Right?

LOG ENTRY: SOL 468

I managed to thread the needle between Rutherford and Trouvelot nicely. Admittedly, the needle was 100 kilometers wide, but hey.

I’m now enjoying my fourth Air Day of the trip. I’ve been on the road for twenty sols. So far, I’m right on schedule. According to my maps, I’ve traveled 1440 kilometers. Not quite halfway there, but almost.

I’ve been gathering soil and rock samples from each place I camp. I did the same thing on my way to Pathfinder. But this time, I know NASA’s watching me. So I’m labeling each sample by the current sol. They’ll know my location a hell of a lot more accurately than I do. They can correlate the samples with their locations later.

It might be a wasted effort. The MAV isn’t going to have much weight allowance when I launch. To intercept Hermes, it’ll have to reach escape velocity, but it was only designed to get to orbit. The only way to get it going fast enough is to lose a lot of weight.

At least that jury-rigging will be NASA’s job to work out, not mine. Once I get to the MAV, I’ll be back in contact with them and they can tell me what modifications to make.