If the maxim for the conscientious camper is to Leave No Trace, anthropologists are arguing for a corresponding approach as humanity ventures out across the solar system. Collecting the trash that homo sapiens litter in space may not always be feasible, they say, but we should at least record their presence and treat them as a heritage artifacts.

The need is all the more urgent as the number and longevity of our missions to Mars increase. So runs the argument of “The emerging archaeological record of Mars”, an article published on December 16 in Nature Astronomy by researchers from the universities of Kansas City, New Mexico State, Cornell, North Carolina State, and the Spanish Astrobiology Center.

These space artifacts include human-operated probes, landers (spacecraft that land), rovers, netting, parachutes, thermal blankets, and helicopters, such as Ingenuity, which flew more than 70 times over Mars during NASA’s 2020 mission. Archaeologists should also record non-portable artifacts, such as human footprints and trackways made by vehicles. Put together, the researchers argue, these represent humanity’s space heritage, one linked to our species’ evolutionary history of migration that leads out of Africa to the moon and beyond.

“As we move forward during the next era of human exploration, we hope to work together to ensure sustainable and ethical human colonization, that protects cultural resources in tandem with future space exploration,” the authors wrote.

Map of Mars showing the fourteen missions to the planet including key sites and examples of artefacts. Photo: Nature Astronomy.

Mankind’s archaeological record on Mars began in 1971 when the USSR’s Mars 2 and Mars 3 crashed on the surface of the red planet along with their PrOP-M rovers. Success was mixed and extremely short-lived; hard landings and a planet-wide sandstorm didn’t help. In 1976, the Americans successfully landed Viking 1 on Mars and operated it for more than six years. Chinese, Japanese, European, and Indian missions to Mars have followed and over the past 50 years researchers estimate 22,000 pounds of human-discarded objects are on the planet.

To date, most of the attention paid to these space artifacts—which we shouldn’t call “space trash or galactic litter,” the authors note—has focused on their potential impact on future missions by polluting the ecosystems of Mars. While these concerns are important, the artifacts should also be considered objects of cultural heritage and the paper calls for greater cooperation between planetary scientists and archaeologists to document and manage the resources.

While the United Nations keeps track of objects launched into space, at present, the authors wrote, there “exists no systematic strategy for documenting, mapping and keeping track of all heritage on Mars.” The thinking runs that Mars represents our species’ first exploration of another planet and any destruction of this record would be permanent.