Homo planetarius
Apollo 15: Commander Dave Scott salutes the flag at Hadley Apennine
Imagine a sinuous sulcus of rover tracks on the Moon from the standpoint of Homo planetarius, an advanced human species, a million years from now. On the lunar surface, where no wind or atmosphere erases the past, they will stand as enduring relics - symbols of immortality. Much like the Mayan or Egyptian pyramids, they will whisper of the mystery and mastery of an ancient, space-faring civilization. Earth will be unrecognizable then, with most of our architectural structures demolished, but the planetary roads will remain unchanged. There will be only one system of lunar roads but many more lunar missions over the next 1000 millennia. How often do we get the opportunity to design and build something that will still be intact millennia later? These are the first roads in space.
The image below is of the landing site for Apollo 17, the last manned mission to the Moon. The rover tracks are still viewable from space, more than 50 years later, and although they meander and loop, are perfectly adequate as a trail for astronauts to follow back to the lunar module (Challenger descent stage).
Apollo 17 landing site
From the Apollo 15 Lunar Surface Journal, EVA 2, Station 4 at Dune Crater:
[Dave Scott - "One of the methods we seriously considered on getting back to the LM was following the tracks back because, if you're over the horizon and your Nav system doesn't work, it's very hard to tell where to go - other than the Sun compass that we had. We used to joke about the old Hansel and Gretel trick."]
[Eric M. Jones - "But, once you were down there, did you also have the feeling that there were sufficient horizon features?"]
[Scott - "Yeah, there are pretty good horizon features; but you can't beat the comfort of the tracks. And, if you're offset, horizon features don't necessarily work."]
[Scott, from the 1971 Technical Debrief - "It was interesting to us concerning the ground's interest in finding our tracks. Every time we headed back from any point, they said, 'Find your tracks and follow them.' I guess there was some doubt as to the Rover Nav system, but I felt very comfortable about where we were. I never felt that we needed to find our tracks. Did you?"]
[Jim Irwin, from the 1971 Technical Debrief - "No. Particularly from the Front, because we could see the LM."]
[Scott, from the 1971 Technical Debrief - "Another factor was the mountains in the background and the horizon. We could pick a point on the mountain and drive towards that point and we knew we were going toward the LM. I never felt disoriented or lost. I think we could have completely lost the Rover Nav system and I wouldn't have had any apprehension about finding the LM."]
[Irwin, from the 1971 Technical Debrief - "Yes; as you remarked, you could see Pluton all the way back. Just head toward Pluton."]
[Scott, from the 1971 Technical Debrief - "We could see Pluton, and we knew the LM was on a slight rise; topographic high, anyway. So I didn't feel tracks were necessary. As a matter of fact, I think we deviated from the tracks to find better routes, or more direct routes."]
[Irwin, from the 1971 Technical Debrief - "Yes. We certainly did on EVA-3."]
[Scott, from the 1971 Technical Debrief - "Well, on EVA-2, also. After Station 4, if we had followed out tracks, we would have had to do some weaving in and out of the craters there."]
[Scott, from a 1996 letter - " (With regard to horizon features), once you see the LM and locate it relative to a distant feature, then you can track the feature and reach the LM without seeing it again."]
Apollo 15: Note that EVA 2 is mostly a straight line, while the other two traverses are loops. That is because the astronauts followed their rover tracks back to the lunar module.
