What route did Mark Watney take on Mars? (spoiler alert)

Saturday , 17, October 2015

I recently saw The Martian in the cinema. The story is based on a book with the same title by Andy Weir. I still have to read the book1, but I found the movie to be quite nice. It can perhaps best be summarized as ‘MacGyver in Space’ and deals with the adventures of astronaut Mark Watney. He was left alone on Mars after a severe dust storm caused the Ares 3 Mars mission he was part of to be aborted. His fellow crew mates thought he was dead and went back to Earth leaving Watney behind.

To be able to get back home (#bringhimhome) he needs to travel great distances on Mars. That triggered my interest: could I calculate the best possible route that Watney might have taken? First I needed to know the locations. Watney is based in Acidalia Planitia at the Ares 3 landing site. I emailed Andy Weir and he told me the location is 28.6306°W and 31.3889°N2.

Watney his first mission is to fetch the Mars Pathfinder, which is located at 33.22°W and 19.13°N. The second mission is to the Ares 4 landing site in Schiaparelli crater. This location was a bit harder to pinpoint. But luckily the people from the HiRISE camera on board the Mars Reconnaissance Orbiter have a special page dedicated to The Martian. One HiRISE image covers the possible future Ares 4 landing site. I chose the center coordinates of this image to be the location of the Ares 4 landing site: 15.2°E and 3.964°S3

Next step is to calculate the most efficient routes from Ares 3 to Pathfinder and from Ares 3 to Ares 4. The data I wanted to use is Mars Orbiter Laser Altimeter (MOLA) on board the Mars Global Surveyor orbiter4. This is almost 500 meter per pixel data, so not the most detailed, but enough to make sure Watney doesn’t bump into the most obvious mountains or falls down steep rims of the larger craters. I asked this question on the Stackexchange website and an answer came back shorty after: use Least Cost Path Analysis5. This method sounded promising and after some tweaking in python and ESRI ArcGIS I was able to get the following result6. As you can see Watney didn’t travel in a straight line.

In reality we would of course need the best resolution elevation data out there. That is the 50 cm/pixel Digital Terrain Models (DTMs) created by matching two overlapping pairs of HiRISE images. Unfortunately, these are only available for a small portion of the Martian surface. In the figure above their locations are shown as the blue strips7. Interestingly both the Ares 3 and Ares 4 locations have coverage of these HiRISE DTMs. Were they used in the movie? As far as I could find the Mars scenes of the movie were shot in Jordan. Ah well, maybe the future explorers of Mars won’t need HiRISE anymore and instead will use data from some fancy advanced future mission? What about a crowdfunded mission to Mars where thousands of cheap drones, sent using CubeSats, will map the surface of Mars in high detail? Drones equiped with LIDAR like the ones shown in this TED talk? Sounds like a plan?