ARTIFACTS IN SPACE, OR SPACE ANTHROPO-ARCHEOLOGY

The purpose of this project is to list all human-made objects that were sent in deep space, way beyond the Earth’s orbit. While most of them are now orbiting the Sun, the planets, the moons, the asteroids and comets, some are permanently set on their surfaces and a few of them are on their way out of the solar system (see illustration below, credit: Olaf Frohn).

Note that the Earth’s artificial satellites are not listed here, except those that were part of an interplanetary mission.

As of 2024, over 5,000 objects have been identified, ranging from large probes to small pins and including spent injection stages, rovers, heat shields, parachutes, dust caps, weights, bolts, lanyards, hand tools, foam blocks, sample bags, burial ashes capsules, memorial items, … you name it. For example, the video sequence above shows how a probe, bound for Mars, successively discards its injection stage, a pair of yo-yo de-spin masses and the kick stage (credit: JPL).

THE DIFFICULT TASK OF MAKING A COMPREHENSIVE INVENTORY

The exact number of artificial objects in outer space will never be known. Many factors rule the game:

  • How objects are numbered, for instance a complex Apollo rover may be counted as one object or split into its detachable elements: antennas, cameras, batteries, seats, console, hand tools carrier, fenders, etc. (see the Apollo 15’s rover in the picture below, credit: NASA);
  • The number of debris resulting from impacts, collisions and spent stage breakups, provided those events will ever be known;
  • The number of objects that emerge from deployments and separation of spacecraft (explosive bolts, lens caps, dust covers, clamp bands, fairings, shrouds, etc.);
  • Untold or unknown events such as classified missions and experiments, private belongings secretly left on the moon by the Apollo astronauts, family items hidden into space hardware by mission staff and technicians, or Apollo hardware unofficially returned to Earth as souvenirs by the astronauts.

Additionally, it is almost impossible to pinpoint most of the orbiting objects, not only because inert items and defunct probes are untrackable, but also because their trajectories are perturbed by the unpredictable orbital mechanics, rendering trajectories calculations useless in the long-term. Thus, some objects are listed on one table but should probably lie on another one.

However, access to Space Agencies records and databases to fetch detailed information about actual flight hardware, exact deployment sequences and other critical information would greatly help establishing more accurate listings.

FIRST OBJECTIVE: PROTECTION OF OUR INVALUABLE OUTER SPACE HERITAGE

All these objects are witnesses of human activity in space and are as precious as archeological items buried several feet underneath us: like Egyptian mummies on Earth, it is important that we protect them against similar dangers for both their historical and scientific values which are beyond estimation (e.g. Perseverance and Ingenuity in the picture below, credits: NASA, JPL):

  • Time and extreme environmental conditions such as micrometeoroids impacts, solar radiation, dust, wide temperature ranges and high pressure for which no design would be powerful enough;
  • Inadvertent destruction and misappropriation as space will become more accessible to private enterprise. And because small items such as cameras, geology tools and tiny detachable parts are more prone to end as souvenirs for the space tourist than large rovers or landers, their vulnerability must be emphasized.

This catalogue, the most accurate to date, is a step in preserving them by establishing what’s actually out there and where it is precisely.

SECOND OBJECTIVE: MITIGATION AND REMEDIATION OF OUTER SPACE DERELICT OBJECTS

DON’T call these relics ‘space junk’! Mass and space exploration are not compatible: a spacecraft can’t afford trailing unnecessary load, so items that are no more useful at one point into the mission become dead weight and must be shaved off quickly. For example, the Apollo astronauts couldn’t clean up the ALSEP sites and bring back home all the packaging (see picture below, credit: NASA): if they had done so it would have been at the expense of the precious lunar rocks and their very short time on the surface doing science. Unfortunately, as of today, there is no other viable option to guarantee mission success and there are no means to retrieve them.

Thus, ‘derelict objects’ is a more appropriate word to qualify them and they can be classified into three groups:

  • Group 1, ‘visual annoyance’ (surface): inert items, such as aluminum parts or soft bags, which have no impact on the environment (see the Apollo 17’s ALSEP site in the picture below, credit: NASA);
  • Group 2, ‘NBCs’ (surface): Nuclear, Biological or Chemical active items (e.g. RTGs, spacecraft batteries or propellant tanks) that can induce pollution or contamination in probable organic or icy worlds such as Venus, Mars, Gas Giants’ Moons, dwarf planets, comets and some asteroids;
  • Group 3a, ‘hazardous objects’ (orbit): hyper-velocity items travelling throughout the solar system, posing a threat to space navigation and to the surface of celestial bodies;
  • Group 3b, ‘hazardous objects’ (surface): debris or loose hardware that may pose as a risk of entanglement to the Rovers.

While all cases should be remediated, both groups 2 and 3a must be emphasized to mitigate consequences. This catalogue is a step in this direction.

ADDITIONAL INFORMATION

In order to ease reading, the data is split into several tables, each referring to a celestial body (sun, planet, moon, asteroid or comet), the location (orbit or surface) and the context of the object (systemic or archeological). Additionally, each table displays the artificial objects in chronological order of deployment. More explanation about the tables layout is available here.

Pictures of the probes and items in space are visible on this page and how probes land on a surface are explained on this one.

The lists are as comprehensive as possible and we’re doing our best to complete and keep them up to date. Any help to improve them will be appreciated. Should you have any question or remark, please drop us a line.