There’s a 1 in 10 chance that someone on Earth will be lethally struck by rocket debris re-entering Earth’s atmosphere in the next decade.
And according to a new study led by researchers from the University of British Columbia (UBC), Canada, the story is worse for those who live closer to the equator, with the chances of a hit as much as three times higher for people living in places like Jakarta, Lagos and Dhaka than their counterparts in Beijing, New York or Moscow.
A very small chance you be hit by space junk, but…
There’s less than a trillion-to-one chance you’ll be hit by space junk, according to most estimates.
That said, one Oklahoman should probably have bought a Powerball ticket after being struck by parts of a Delta II rocket while out walking in 1997.
And while the odds that you’ll be walloped by astro trash are minuscule, there are many documented close calls.
In fact, the publication of UBC’s research in Nature Astronomy comes 43 years to the day that the coastal town of Esperance in Western Australia woke to find fragments of NASA’s Skylab satellite scattered around it. The Esperance shire council opted to fine NASA for littering in response, an event comically commemorated in 2019 when a Las Vegas radio station raised $400 to finally pay the debt.
But falling space junk is no laughing matter – take China’s Long March 5B rocket.
It made headlines in 2020 when buildings in an Ivory Coast village were damaged by the rocket’s returning debris. And nations like Ivory Coast are more likely to be in the firing line of uncontrolled debris, according to the UBC researchers.
“The risk on the ground is borne disproportionately by populations close to the equator,” explains lead author Professor Michael Byers from UBC.
“We realised at one point that this was another example of the exportation of risk from wealthy ‘northern’ countries to less wealthy ‘southern’ ones.”
Space debris is a national liability
NASA estimates 80% of the planet’s population is “unprotected” or “lightly-sheltered” from the impact of falling space junk.
Last year, its administrator Senator Bill Nelson called on spacefaring nations to “minimise the risks to people and property on Earth of re-entries of space objects and maximize transparency regarding those operations”.
Those comments were in response to another uncontrolled return of Long March 5B remnants, of which there are many incidences.
So who is responsible for space junk when it hits home?
It’s not NASA, Space-X or any other launch entity, but the national government of the country from where the object originated.
“The Liability Convention imposes absolute liability for damage on Earth,” says Duncan Blake, special counsel in space law at IALPG, an Australian specialist air and space law firm. “What it means is there is no need to prove any fault whatsoever. What you need to prove is who is the launching state in respect of that space object.
“Once you know who that is, they are liable no matter what.”
That means in the case of a satellite launched from Australia crashing down somewhere on Earth, it would be the federal government that bears responsibility for any damage caused. To protect itself, a government can require launch entities to be insured against that outcome.
“What that means […] is the government needs to make sure the space enterprise that has a licence [to enter space] is in a position to indemnify the Australian government, and therefore the Australian people,” explains Blake.
“The way in which it does that is that someone getting a licence or permit has insurance up to a certain level, or sufficient financial resources to pay for compensation.”
What goes up, must (eventually) come down
Given an increasing number of space launches from world governments and private enterprise, space – or at least the part of it closest to Earth – is becoming crowded.
Right now, there are over 600 rocket bodies that orbit within 600 kilometres of Earth – the majority of which originate from the United States (41% share) and China (17%).
The European Space Agency reports there is more than 9900 tonnes of space objects orbiting Earth. Over 32,000 space objects are regularly tracked.
And there’s inconsistency in the risk thresholds set by launch organisations and national governments.
For instance, NASA space programs aim to limit the risk of human casualty to odds of less than 1 in 10,000. The United Nations’ space debris mitigation guidelines stipulate “due consideration should be given to ensuring that debris that survives to reach the surface of the Earth does not pose an undue risk to people or property, including through environmental pollution caused by hazardous substances”.
But that is not an odds-based safeguard.
In Australia, the Space (Launches and Returns) (General) Rules 2019 provide a framework for the Australian government to approve space-based activity within its jurisdiction, including returning space objects. Among a range of regulatory processes required for ministerial approval, entities seeking to send objects into space must complete a risk hazard analysis under Australia’s flight safety code.
To avoid cases like those in Esperance or Ivory Coast, launch companies can reduce their risk by building craft for controlled re-entry.
Such craft carry additional fuel, which reignites larger propulsion systems at the end of the craft’s life. This enables it to re-enter Earth’s atmosphere at steeper angles – giving mission controllers greater targeting precision to find a safe place for final impact.
It’s an investment UBC’s scientists say would better protect nations at greater risk of damage from returning objects.
But that requires the small number of spacefaring nations to agree to rules that stipulate how material should return to Earth.
Byers points to the Montreal Protocol that helped close the hole in the ozone layer, or the introduction of double hull tankers in response to the Exxon Valdez oil spill as examples of nations collaborating on international standards.
“First of all […] it’s a solvable problem,” he says.
“Secondly, the global south has a moral position. And thirdly, they have the capacity to initiate these negotiations. And I’m hopeful that something will occur.
“We’re only talking about a couple of dozen actors: countries and space companies.
“So this should be an easy problem to solve. The challenge is that, of course, it involves slightly increased costs. The way you do that is through a multilateral treaty, but none of this is new.”
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