Mars is littered with junk. Historians want to save it.

No astronaut has ever stepped foot on Mars, but that doesn't mean humans haven't left their mark — literally. 

Since 1971 when the Soviet Union's Mars 2 spacecraft crash-landed onto the Red Planet, people have littered the Martian surface with man-made junk, quite a feat from an average of 140 million-miles away. Broken spacecraft debris, parachutes, and rover tracks are just some of the ways our species has disrupted the foreign environment — not to mention the hardy Earthling bacteria it has inadvertently sent there. 

Now a group of anthropologists, led by University of Kansas researcher Justin Holcomb, is calling for NASA and fellow space agencies to create a catalog of known objects on the neighboring planet, before its harsh environment batters and buries the artifacts. Existing databases, like the United Nation's Register of Objects Launched into Outer Space, could provide the framework for tracking materials, the team proposes. 

"It's not trash; it's actually really important," said Holcomb in a statement. "The solution to trash is removal, but the solution to heritage is preservation. There's a big difference."

Usually when scientists talk about "space junk," they are referring to the immense amount of debris orbiting the planet that endangers satellites and threatens the safety of astronauts on the International Space Station. The Department of Defense tracks about 27,000 artificial objects near Earth that are four inches or larger, but many smaller pieces can't be detected. 

NASA has estimated there are about 500,000 marble-size objects that aren't monitored. That's worrisome because a tiny fleck of garbage, like a screw zooming at 15,700 mph, could be problematic or disastrous for a spacecraft.

But the idea of space junk as an archaeological record of humanity is not an entirely new concept, either. 

NASA published an inventory in 2012 of about 800 items discarded or installed on the moon. The catalog includes astronaut poop, scoops and tongs, moonquake experiments, a hammer, vomit bags, orbiters, cameras, mirrors, golf balls, cosmic ray detectors, shoes, dead rovers, and $2 bills.

The purpose wasn't really to take accountability for the mess but to keep a log of the items sprawling the moon so they can be mapped and preserved. And, yes, Neil Armstrong and Buzz Aldrin's poop are among those historical artifacts. Some even consider them science.

In the dozen years since the lunar catalog was released, much has changed. Now commercial companies are crashing — and sometimes landing — on the moon, too. Five years ago, for example, Israel's failed Beresheet landing spilled dehydrated tardigrades, aka microscopic "water bears," among its crashed cargo. And notoriously secretive nations who have become spacefarers have left behind their own share of trash. 

Right now there are no plans to update the moon catalog, Brian Odom, NASA's chief historian, told Mashable. 

"Certainly not a bad idea," he said, "but nothing is in the works at the moment." 

For Mars, archaeologists are less concerned about competing nations and companies disrupting landing sites as they are about nature. Geoarchaeology is the study of how geology affects archaeological sites. But scientists know little about how cosmic radiation, ice action, and dust storms — the conditions of another world — will affect these objects over time. 

Scientists are aware of the hazards of dust devils churning up Martian dirt. About 12 years ago, the Mars Reconnaissance Orbiter caught sight of an extraordinary one with a plume stretching 12 miles into the sky. Dust devils, typically smaller than tornadoes, are whirlwinds that make a funnel-like chimney, channeling warmer air up and around. Sometimes they can blow dust off surfaces, but they're not reliably helpful in that way.

The Red Planet has already caked soil on the solar panels of NASA's InSight lander, which stopped working in 2022. It's now heavily camouflaged in the desert. And a broken blade of the Ingenuity helicopter, which suffered a fatal mishap in January, is barely visible, due to its relatively small size in the vast environment. 

Holcomb, whose team authored the paper proposing a Mars catalog in Nature Astronomy this week, is most worried about sand dunes.

"The Spirit Rover, for example, is right next to an encroaching dune field that will eventually bury it," he said. "Once it's buried, it becomes very difficult to relocate.”

NASA's Mars Exploration program has no plans to centralize an inventory of objects, but doing so may not be as difficult as one might assume. Each Mars mission team keeps track of its own hardware, Karen Fox, an agency spokeswoman, told Mashable; the lists just haven't been combined. 

"These artifacts are very much like hand axes in East Africa or Clovis points in America," Holcomb said. "They represent the first presence, and from an archaeological perspective, they are key points in our historical timeline of migration."