Picture yourself as a future settler on Mars. You gaze across a cold, barren landscape painted in rusty red and gray hues. But it’s not all dull. Here and there, faint tracks left by rover wheels cut through the dust. Nearby, a broken probe lies weathered and motionless. While these remnants may seem like mere debris, some scientists see them as invaluable artifacts of human exploration.

Humans have been reaching toward the Red Planet for over half a century. In that time, our attempts have left a subtle, scattered presence: old probes, rover tracks, and bits of metal. Now, a new comment in Nature Astronomy pushes a surprising idea: that we should treat these leftovers as historical artifacts rather than scraps.

“Homo sapiens are currently undergoing a dispersal, which first started out of Africa, reached other continents, and has now begun in off-world environments,” said Justin Holcomb, an anthropologist at the University of Kansas, and the work’s lead author.

Holcomb argues that what humans have left on Mars isn’t a bunch of broken machines. Instead, it’s a developing record of our first steps onto a different planet, just as our ancestors left behind traces of existence millennia ago.

“We’ve started peopling the solar system,” Holcomb said. “And just like we use artifacts and features to track our movement, evolution and history on Earth, we can do that in outer space by following probes, satellites, landers and various materials left behind. There’s a material footprint to this dispersal.”

We keep sending stuff to Mars

The idea might sound strange at first—no human has set foot on Mars. But Holcomb and his colleagues trace our Martian imprint back to 1971, when the Soviet Union’s Mars 2 became the first spacecraft to crash-land on another planet. Though the mission failed, it marked the beginning of our physical presence on Mars.

Since then, other missions have followed. The Viking landers in the 1970s successfully touched down and returned images. Though they proved vastly successful — indeed the precursors to more advanced missions — their metal bodies are now defunct. More recently, NASA’s Perseverance rover dropped pieces of protective gear on the ground, including Dacron netting, a material from its thermal blankets.

What looks like litter to some is, to archaeologists, a record of how we engage with Mars.

“These are the first material records of our presence, and that’s important to us,” Holcomb said. “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.”

Planetary geoarchaeology

The paper dives into the emerging concept of “planetary geoarchaeology.” On Earth, archaeologists pair geology with human artifacts to understand how landscapes, climate, and time shape what remains. The authors hope to use a similar approach on Mars.

Each rover that breaks down, every lander that winds up covered by dust and sand, is entering a new geological record. One day, explorers or robotic missions might dig these objects up like we do pottery shards on Earth, examining how environmental forces slowly altered them.

On Earth, we can trace human movement and cultural change by following the stone tools and pottery fragments scattered across continents. On Mars, our presence may follow a similar pattern: early wrecks and landers as initial markers, followed by more organized expeditions leaving behind increasingly complex gear. Each era might show advancements in engineering, understanding of Martian conditions, and how our priorities shifted over time.

Holcomb’s team also suggests that treating these objects as artifacts can also shape how we plan future missions.

“Missions to other planets must consider this in their planning,” Holcomb said. “They won’t land in areas that could disturb these sites. They’ll think about them differently than just trash lying around. That’s probably the main thing. From an academic perspective — which is what these papers aim to address — what are the implications? We need to track our species’ movements through space and time, and we do that through stratigraphy.”

Holcomb’s argument for safekeeping traces of human exploration on other planets builds on earlier lunar work, where he argued for the declaration of a “lunar Anthropocene” — or an age of human dominion over the moon’s landscape.

“On the moon, we argued we could create an Anthropocene — a human age,” he said. “On Mars, we don’t think there’s an Anthropocene, but there is an archaeological record that needs to be a stratigraphic horizon, allowing us to place this material into a framework. And of course, we could do this across the solar system.”

Holcomb advocates establishing a methodology for tracking and cataloging human material on Mars and subsequent planets humans might visit, perhaps via an already existing database like the United Nations Register of Objects Launched into Outer Space.

“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,” Holcomb said. “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.”