Trying to better understand the geologic history of the Moon was one of the highest priorities of the Apollo science team. Sending astronauts to the Moon meant that rock formations could be compared to those on Earth, photos and observations could be taken of the surface, and best of all, samples could be collected and brought back home for analysis. To maximize what data and samples could be collected by the astronauts in a limited amount of time, areas with high geologic variability were of the highest scientific value.

Unfortunately, the areas that were most interesting to the scientists also tended to be a bit of a journey from anywhere the engineers identified as safe for landing (in short, without topographic hazards). For the first few Apollo missions, the crew had to walk to any spot they wanted to observe. While taking any step on the moon was, as Armstrong so properly put, a “giant leap for mankind,” many aren’t aware of how few steps the first astronauts actually took, especially compared to the later Apollo missions. Aldrin and Armstrong never ventured more than about a tenth of a mile (~650 feet) away from the Eagle. However, for Apollo 15, 16, and 17, the USGS’s beloved Grover (the Geologic Lunar Rover) mobilized the astronauts like never before. This meant that astronauts could travel farther and visit more geologically complex locations compared to earlier missions. With the pool of accessible, safe, and geologically interesting landing areas drastically increased, the mission teams decided to send the last three missions to Rima Hadley, Descartes, and Taurus-Littrow, respectively.

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The Apollo 11 Traverses (upper left) did not travel more than ~1/10th of a mile from the LEM. The Apollo 17 Traverses (base image), on the other hand, traveled 22.2 miles in Grover. This map illustrates the difference in scale between the two missions. Photo Credit: NASA/GFSC/ASU, USGS Astrogeology

Check out NASA’s timeline of all the Apollo Missions here!

While the astronauts got their hands dirty training in the field, the mappers at the USGS got to work on a series of official USGS lunar landing site maps, so the astronauts on the moon would have a scientific roadmap of sorts to lead them to regions where the most valuable and impactful observations could be made. Geologic maps of the lunar landing sites that were prepared in anticipation of these missions contained not one, but two “nested” maps of each landing site. The smallest scale (largest area) map shows a broad region around and including the landing site. The largest scale map (smallest area) is a zoomed in view of the immediate landing site with much more detail than the regional map. 

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The nested quality of USGS IMAP 800 is exemplified in this image. The inset of the 1:50K (smaller area, larger scale) landing site map is outlined on the 1:250K (larger area, smaller scale) map of the Taurus Littrow area. Photo Credit: USGS Astrogeology

Why was one map not enough, though? Could the mappers at the USGS not just fit all the information onto one map?

Let’s think about why they provided multiple maps using an Earth-based example. Imagine that you’re taking a road trip to an amusement park for a vacation, and you can only use paper maps to get there. All you know is that the park is in “Fun City,” which is located in “Adventure County,” but otherwise, you have no idea how to get there.

To find where the amusement park is, you would start with a state-wide map. Depending on how large the state is, a map of the entire state might not show Fun City, and it certainly doesn’t show the city in enough detail to get to the park. Instead, you may need to use the state map to narrow down which interstates to take to get to Adventure County. To find where Fun City is, you may need a slightly larger-scale regional map of just Adventure County, where you could then determine which local highways you need to take to get to Fun City. 

Once you arrive in Fun City, your regional map shows the amusement park on the map, but the roller coaster symbol is taking up so much room graphically that you can’t see any of the cross-streets around the park. To find where the amusement park is, you need an even larger-scale map of Fun City itself, otherwise you would be driving around the area for hours to just find the park. 

Once you’ve finally parked at the amusement park, you look back down at the welcome packet they’ve given you - there’s a map of the park included! Even within the park itself, you would want a map to show you to your favorite rides, the hotel you’re staying at, the way to restaurants, or even just the path back to your car! 

Using this example, we can see why nested maps are a necessity, and how different map scales show different information. You’d never be able to use the state map to find a restaurant within the amusement park, and likewise, you’d never be able to use the detailed map of Fun City to get directions to another state. If we needed four maps just to get to our simulated amusement park vacation, to think that the astronauts traversed around with only two on the moon is mind-blowing. It’s easy to forget there is no GPS on the Moon!

The nesting of lunar maps using different map scales was very deliberate, and not just an attempt to make the astronauts rifle through multiple maps like we just did on our fictional road trip. To properly know where to land and complete short trips, the detailed, large-scale (small area) map is a necessity. For the longer traverses involved in the Apollo 15, 16, and 17 missions, more context was needed for the astronauts to explore outside of their immediate landing site. This need was met by the regional small-scale (large area) maps. In fact, Apollo 17 still holds the record for greatest distance travelled from a spacecraft during an EVA of any kind. They traveled 4.7 MILES away from the LM Challenger!

As we plan for the upcoming Artemis missions, the same concerns about landing sites and mapping that the Apollo science teams faced are just as prominent as they were 50 years ago. Artemis III will land in a region of high geologic interest and variability, which is home to potential water-ice deposits. Due to the proximity to the lunar south pole, the potential Artemis landing sites come with their own set of challenges, including high angle shadows and extremely variable temperature and light conditions. Thirteen candidate sites are being assessed for landing, and the challenges, considerations, and on-the-ground changes made to plans and maps during the Apollo era can be used as brilliant proxies in the planning process for Artemis, especially with the nested maps of the final few missions to the moon.

The USGS Planetary Geologic Mapping Program has continued digitizing Apollo-era maps, which are currently only available in hard copy, and making these maps available as web-based interactive maps. Now, you can explore the new interactive maps of the Apollo 15, Apollo 16, and Apollo 17 landing sites that were recently digitized by W. Brent Garry’s team. Digitizing efforts are ongoing, so keep an eye on our interactive map search tool for more interactive maps of the Moon!