It has been a year this week since Jock Wallace and Mick Miners found pieces of a SpaceX capsule trunk in their paddocks near Dalgety in NSW.
More pieces were found over the following weeks to months, including much further away, out to Tumbarumba on Jordan Hobbs' property.
It thrust the discussion of space junk into the spotlight here.
How we manage objects in space, what we do to dispose of them, and how we prevent space junk in the first place have all been part of the discussions.
One of the best options we have at this point to solve space junk is by having it land in the ocean.
Then last week, a large cylinder washed up on a beach north of Perth, bearing a resemblance to parts of an Indian rocket. However, trying to figure out what it was, and who it belonged to, was less straightforward.
With pieces of the SpaceX capsule trunk, it was being tracked in space, and its flight path was well known. It was also seen across a large area of NSW re-entering on a Saturday morning. And, finally, there were part numbers to confirm who it belonged to.
However, the piece that washed last week didn't have any of that.
It was not a piece of known junk being tracked, nor had people seen it re-enter. It also landed in the ocean so where it was found was not where it landed on Earth and couldn't be tracked to a flight path.
Rockets have multiple parts, called stages.
The first stage is what most people picture as the rocket booster. After the fuel is used in it, the stage or rocket part separates and falls back to Earth, landing in the ocean.
The second stage then turns on and, again, once its fuel is consumed, falls back to Earth. And then often a third stage repeats this process.
These stages, and the subsequent pieces that separate, never fully make it into orbit around the Earth. They fall back to Earth, usually during the launch, landing in the ocean as junk, usually sinking to the bottom.
A number of companies are working on recovering these parts. SpaceX famously designed their rockets to come back down and land. A feat of engineering, it means that they do not end up in the ocean, and can be reused.
RocketLab in New Zealand has been recovering their rockets from the ocean when they splash down, or even using a helicopter and catching them mid-air like a giant arcade claw machine game.
However, the majority of parts still do fall into the ocean. And apparently, not all of them sink, as was the shock discovery last week.
Dumping bits of space junk in the ocean, either from the rocket on the way up, or as the satellite or other part re-enters the Earth's atmosphere, is the industry standard. At the end of the decade, the International Space Station will be de-orbited and land in the ocean.
However, if this event in Western Australia has shown us anything, this is not the best solution, and we need to do better.
- Brad E. Tucker is an Astrophysicist and Cosmologist at Mt Stromlo Observatory and the National Centre for the Public Awareness of Science at the ANU.
