It’s not often that I highlight the work of anthropologists on Centauri Dreams. But it’s telling that the need to do that is increasing as we continue to populate the Solar System with human artifacts, which are after all the province of this discipline. I’ve often wondered about the fate of the Apollo landing sites, originally propelled to do so by Steven Howe’s novel Honor Bound Honor Born and conversations with the author ranging from lunar settlement to antimatter. Long affiliated with Los Alamos National Laboratory, Howe is deeply involved in antimatter research through his work as CEO and co-founder of Hbar Technologies.

In my conversations with Howe almost twenty years ago while writing my original Centauri Dreams book, he was asking what would happen if commercial interests decided to exploit historical sites from the early days of space exploration. The question is still pertinent. Imagine Armstrong and Aldrin’s Eagle subjected to near-future tourists prying off souvenirs or putting footprints all over the original tracks left by the astronauts. Some kind of protection is crucial before technology in the form of cheap access to the lunar surface becomes available, and that may be a matter of decades more than centuries. The point here is to get the policies in place before the contamination can occur.

The Outer Space Treaty of 1967 is ratified by over 100 nations, but while offering access for exploration to all nations doesn’t address the preservation of historical sites. UNESCO’s World Heritage Convention does not apply to sites off-planet, while NASA’s 2011 protection guidelines offer useful ‘best practice’ solutions for protecting sites, but these are entirely voluntary. The Artemis Accords are bilateral agreements that offer language toward the protection of historical sites, but again are non-binding. So the Moon stands as an obvious example of an about to be exploited resource for which we lack any mechanisms to protect places future historians will want to examine.

Or think about Mars, as Kansas anthropologist Justin Holcomb does in a paper just published in Nature Astronomy. As we are increasingly putting technologies on the surface, we are building up yet another set of historical sites that will be of interest to future historians. This is important stuff even if the equipment is quickly rendered inert and soon obsolete, and it’s worth taking an anthropologist’s view here – we’ve learned priceless things about the past through the study of what a civilization thought of as materials fit only for the garbage dumps of the time. What will future scholars learn about the great era of Mars exploration that is now well underway?

“These are the first material records of our presence, and that’s important to us,” says Holcomb. “I’ve seen a lot of scientists referring to this material as space trash, galactic litter. Our argument is that it’s not trash; it’s actually really important. It’s critical to shift that narrative towards heritage because the solution to trash is removal, but the solution to heritage is preservation. There’s a big difference.”

Image: Map of Mars illustrating the fourteen missions to Mars, key sites, and examples of artifacts contributing to the development of the archaeological record: (B) Viking-1 lander; (C) trackways created by NASA’s Perseverance rover; (D) Dacron netting used in thermal blankets, photographed by NASA’s perseverance rover using its onboard Front Left Hazard Avoidance Camera A; (E) China’s Tianwen-1 lander and Zhurong rover in southern Utopia Planitia photographed by HiRISE; (F) the ExoMars Schiaparelli Lander crash site in Meridiani Planum; (G) Illustration of the Soviet Mars Program’s Mars 3 space probe; (H) NASA’s Phoenix lander with DVD in foreground. Credit: Justin Holcomb.

In August of 2022, the Mars rover Perseverance encountered debris scattered during its landing a year earlier. Our Mars rovers repeatedly have come across heat shields and other materials from their arrival, while the wheels of the Curiosity rover have left small bits of aluminum behind, the result of damage during routine operations. Perseverance dropped an old drill bit in 2021 onto the surface as it replaced the unit with a new one. We can add in entire landers, intact but defunct craft like the Mars 3 lander, Mars 6 lander, the two Viking landers, the Sojourner rover, the Beagle 2 lander, the Phoenix lander, and the Spirit and Opportunity rovers. A 2022 estimate of spacecraft mass sent to Mars totals almost 10,000 kilograms (roughly 22,000 pounds), with 15,694 pounds (7,119 kilograms) now considered debris as the material is non-operational.

Image: This image from Opportunity’s panoramic camera features the remains of the heat shield that protected the rover from temperatures of up to 2,000 degrees Fahrenheit as it made its way through the martian atmosphere. This two-frame mosaic was taken on the rover’s 335th martian day, or sol, (Jan. 2, 2004). The view is of the main heat shield debris seen from approximately 10 meters away from it. Many rover-team engineers were taken aback when they realized the heat shield had inverted, or turned itself inside out. The height of the pictured debris is about 1.3 meters. The original diameter was 2.65 meters, though it has obviously been deformed. The Sun reflecting off of the aluminum structure accounts for the vertical blurs in the picture. The image provides a unique opportunity to look at how the thermal protection system material survived the actual Mars entry. Team members used this information to compare their predictions to what really happened. Credit: NASA.

The human archaeological record on Mars began in 1971 with the crash of the Soviet Mars 2 lander. The processes that affect human artifacts in this environment are key to how they degrade with time, and thus how future investigators might study them. We’re in the area now of what is known as geoarchaeology, which has ripened on Earth into a sub-discipline that analyzes geological effects at various sites. Holcomb points out that Mars has a cryosphere in the northern and southern latitudes where ice action would alter materials even faster than Martian sands. But don’t discount those global dust storms and dune fields like the one that will likely bury the Spirit Rover.

So we have many sites to protect from future human activities as well as a need to catalog the locations of debris that will disappear to view through natural processes over time. This is satisfyingly long-term thinking, and I like the way Holcomb describes extraterrestrial artifacts (left behind by us) in terms of our own past:

“If this material is heritage, we can create databases that track where it’s preserved, all the way down to a broken wheel on a rover or a helicopter blade, which represents the first helicopter on another planet. These artifacts are very much like hand axes in East Africa or Clovis points in America. They represent the first presence, and from an archaeological perspective, they are key points in our historical timeline of migration.”

Migration. Think of humans as a species on the move. Outward.

Image: Impact and its aftermath. What would a future anthropologist make of the materials found at this site? And how would it affect a future history of human exploration of another world? Credit: NASA.

In terms of mission planning, there is a pathway here. It would be best to avoid operations in sites where previous technologies were deployed, just as we wrestle with issues like those tourists on the Moon. Holcomb argues that we need to develop our methodologies for cataloging human materials on other planetary surfaces, and it’s obvious that we want to do that before such materials become prolific. So perhaps we should start seeing our space ‘debris’ on Mars as the equivalent of those Clovis points he mentioned above, which are markers for the Clovis paleo-American culture.

It always seems unnecessary to do analysis like this until the need surfaces with time, by which point we have let much of the necessary spadework remain undone. But on a broader level, I’m going to argue that thinking about the long-term stratigraphy of space exploration is another way we should engage with the reality of our species as multi-planetary. For that is exactly what we are headed for, a species that begins to explore its neighbors and perhaps establishes colonies either on them or in nearby orbits. That this process has already begun is obvious from the deluge of data we have already accumulated from the Moon all the way out into the Kuiper Belt.

Image: A historical site in context. Seen at the center of this image, NASA’s retired InSight Mars lander was captured by the agency’s Mars Reconnaissance Orbiter using its High-Resolution Imagine Science Experiment (HiRISE) camera on Oct. 23, 2024. The images show how the dust field around InSight – and on its solar panels – is changing over time. Sites like this will inevitably be obscured by such a rapidly changing planetary surface. Credit: NASA/JPL-Caltech/University of Arizona.

We need to stop being so parochial about what we are engaged in. Let’s be optimistic, and assume that humanity finds a way to keep migration going. The ancient middens that are nothing more than garbage dumps for early cultures on Earth have shown how valuable all traces of long vanished cultures can be. We need to preserve existing sites on other worlds and carefully ponder how we handle explorations that can, as they did in the American west, turn into stampedes. That we are talking here about preservation over future centuries is just another reminder that a culture that survives will necessarily be one that pays respect not only to its growth but to its history.

The paper is Holcomb et al., “Emerging Archaeological Record of Mars,” Nature Astronomy (16 December 2024). Abstract.