A Soviet-era spacecraft that never made it to Venus more than 50 years ago is finally about to plunge back to Earth.
That's according to academic and satellite watcher Marco Langbroek from Delft Technical University in the Netherlands, who has been keeping an eye on the Soviet spacecraft called Kosmos 482 for the past few years.
So, as we get closer to the deadline, here are five quick questions on Kosmos 482, and what you need to know about the falling spacecraft.
What is Kosmos 482?
The lander, called Kosmos 482, was part of the Venera program to gather information about Venus.
Other probes in that program — such as Venera 9 — took some of the only pictures ever captured of the Venusian surface.
But Kosmos 482 wasn't so lucky.
On March 31, 1972, it launched, and successfully made it into Earth's orbit.
But, according to reports, during the second stage of the mission an incorrectly set timer botched the job, and the spacecraft has stayed in Earth's orbit ever since.
The spacecraft had already split into four pieces, and it's now thought that the object is just one of those pieces — the landing module.
According to Dr Langbroek, modelling suggests the object is about 480 kilograms and one metre in size.
When will it re-enter the atmosphere?
Kosmos 483 has had a good 53 years up there, but all things that come up must come down, and Dr Langbroek's modelling suggests that'll be May 10, give or take a couple of days.
Astronomers had known for a while that the spacecraft was soon to make its descent.
In the 1970s, the highest point of the orbit was almost 10,000 kilometres above Earth's surface, but now it's below 400km, and rapidly dropping.
The closer it gets to re-entry, the more information we'll have about the exact date and time.
Where will it land?
Dr Langbroek said it's quite possible that the lander will survive re-entry because it was built to withstand a descent through the carbon-dioxide-thick atmosphere of Venus.
But at this point in time it's too early to tell where the spacecraft will land — or if it will burn up before landing.
Experts doubt the parachute system would work after so many years and the heat shield may also be compromised after so long in orbit.
It would be better if the heat shield fails, which would cause the spacecraft to burn up during its dive through the atmosphere, Jonathan McDowell at the Harvard-Smithsonian Center for Astrophysics said.
But if the heat shield holds, "it'll re-enter intact and you have a half-ton metal object falling from the sky", Dr McDowell said.
If the probe does survive its firey re-entry, Dr Langbroek said it could come down anywhere between 51.7 degrees north and south latitude, or as far north as London and Edmonton in Alberta, Canada, almost all the way down to South America's Cape Horn.
But since most of the planet is water, "chances are good it will indeed end up in some ocean", Dr Langbroek said.
A lot of space junk ends up in a remote part of the Pacific known as the "spacecraft cemetery".
But spacecraft making an uncontrolled re-entry can land anywhere. In 2022, debris from an out-of-control Chinese rocket landed in the Indian Ocean.
Parts of a SpaceX spacecraft were found on farms in the Snowy Mountains in 2022, and part of a SpaceX rocket crashed into Poland earlier this year.
Should I be worried?
Probably not.
"While not without risk, we should not be too worried," Dr Langbroek said.
The object is relatively small and, even if it doesn't break apart, "the risk is similar to that of a random meteorite fall, several of which happen each year. You run a bigger risk of getting hit by lightning in your lifetime".
The chance of the spacecraft actually hitting someone or something is small, he added, "but it cannot be completely excluded".
The object is likely to be tracked until it lands, including when it finally re-enters the atmosphere.
Alice Gorman, a space archaeologist at Flinders University, said that if bits of it do make it to Earth and land in Australia, there are some things to be aware of.
"Don't touch it, because sometimes there are toxic elements," she said.
"Report it immediately to the Australian Space Agency, and they will then enter negotiations with the Russian government."
De-orbited space objects that make it back to Earth are owned by the country that sent them up into orbit, under the Outer Space Treaty.
The first two parts of Kosmos 482 landed in New Zealand just a few days after it launched, but the Russians refused to claim them.
"They can't pretend it's not theirs this time," Dr Gorman said.
Is this going to happen more often?
This 53-year-old spacecraft is a "pretty unique interplanetary mission" according to Dr Gorman, so re-entries like this are going to remain rare.
"There's 26 locations on Venus where human spacecraft have landed," she said.
"But there's a hell of a lot of Russian spacecraft that never made it to Venus. This isn't the only failed one."
Today though, interplanetary spacecraft failures are not the only thing we have to worry about.
Earth has many more satellites in orbit than at any other point of history.
While most of these satellites will burn up in the atmosphere, some will make it back to the ground.
"There is going to be a lot more [space junk] in the future," Dr Gorman said.
ABC/AP
