A decades-old Soviet spacecraft originally bound for Venus will crash down to Earth within the next 48 hours, according to experts.
They've been tracking the progress of Kosmos 482 — a 500-kilogram failed probe that was launched 53 years ago.
Tracking a space object that's hurtling around Earth every hour and a half is no easy task, but predicting where it will land days ahead of time is almost impossible, according to Bill Barrett, an orbital expert from Asia Pacific Aerospace Consultants.
"It's very hard just to predict when something like this is going to come back … [it's] one of the hardest things in orbital mechanics," he said.
So what do we currently know, how do experts track the spacecraft, and why is it so hard to predict when and where it will crash?
When will Kosmos 482 crash?
Latest predictions suggest Kosmos 482 may land sometime on Saturday (Australian time) but there is a window of uncertainty either side of that so it may land even earlier.
Currently, Kosmos 482 is circling the planet at an orbit of around 140 kilometres at its lowest and 260km at its highest.
This is rapidly dropping as it tumbles around the Earth, and experts predict the probe will soon hit the point of no return.
Studies show this point for spacecraft like Kosmos 482 is approximately 125km above Earth.
Aerospace Corporation, a federally funded space organisation in the US, has been using publicly available radar data supplied by the US Space Surveillance network to track the out-of-control probe.
At time of publishing, it predicted the Kosmos 482 will land at 12:37 PM AEST on Saturday, May 10, with 16 hours leeway either side.
But other experts, such as Marco Langbroek at from Delft Technical University in the Netherlands, who has been tracking the object since 2019, suggests that the spacecraft might come down about 5 hours later, plus or minus 20 hours.
That means the spacecraft could crash back to Earth as early as 8pm AEST Friday.
"Over the past months, [our modelling] persistently pointed to re-entry within a few days of May 9 or 10," he said.
Where will the probe crash?
It's tricky to exactly predict when an object like Kosmos 482 will come down, but that pales in comparison when trying to work out where it might land.
Aerospace Corporation has created a prediction map that highlights the predicted path — or ground track — of Kosmos 482 during the re-entry window, which appears to cover a lot of the Earth, including parts of Australia.
But don't panic, in reality these tracks only cover a small area, according to Aerospace Corporation engineer Glen Henning.
"Any of the gaps between the ground tracks are basically safe. Anything further north or further south is basically safe," he said.
As we get closer to re-entry the number of tracks on the map will reduce and the gaps between them will get bigger.
"But there's still going to be multiple ground tracks leading up to that final prediction. And it still could be anywhere along that [last] ground track up until re-entry," Mr Henning said.
Even then, it's a guessing game where the probe will end up until it actually crashes or burns up above Earth.
You can check the current location of Kosmos 482 here, and this will continue to be updated until the spacecraft hits the atmosphere, when the tracking will no longer be accurate.
What is the chance it will land in Australia?
It is possible, at this point, the probe could crash somewhere in Australia, but it "largely passes over open land," according to Mr Barrett.
"The satellite orbits over Australia during those windows indicates that the satellite does not pass over any major cities in Australia on those orbits," he said.
"The risk of the re-entry affecting a major population centre in Australia … is low."
However, the experts warn that if it does land nearby you, it is recommended to not touch it, and let the Australian government know as soon as possible.
The map will continue to get updated closer to the re-entry, which you can keep an eye on here.
Because so much of the Earth is covered in water, it is most likely to land in the Ocean, as recent uncontrolled re-entries of Long March 5B and the Tiangong-1 Space Station did.
And even if it does land on solid ground, Aerospace Corporation predictions suggest there's a risk of just 0.4 per 1000 of serious injury or death to anyone on Earth.
Why is it so hard to pin down the predictions?
There are a number of factors that affect the accuracy of calculations, according to Mr Barrett.
"Where's the Earth's atmosphere at the moment? … Do we have our calculations right? Do we have the mass of the vehicle right?
"Subtle nuances can make a huge difference."
But most of the variation and uncertainty about when — and therefore where — Kosmos 482 will go down, is caused by the Sun.
"[The Sun] pretty much does whatever it wants to do. It's very hard to predict," Aerospace Corporation's Marlon Sorge, who focuses on orbital and re-entry debris said.
Solar storms — when there's an increase of particles and radiation from the Sun — can puff up Earth's atmosphere.
A "bigger" atmosphere that extends further into space means the spacecraft will hit it earlier, and atmospheric drag will then pull down the spacecraft quicker, Dr Langbroek said.
"If solar activity the coming days is higher than predicted, [Kosmos 482] will come down earlier. If it is lower, it will come down later," he said.
As it gets closer to Saturday, the time frames of when the spacecraft will land should narrow, mostly because the teams can better implement solar data into their models.
Will I be able to see it?
You can track the space probe's progress on sites such as Heavens Above and N2YO, but you might not see much at all — even if you are near the final ground track.
The probe was built to withstand the atmosphere of Venus, so some experts predict it may not break up as it re-enters Earth's atmosphere.
Photographs taken in both 2014 and 2024 by amateur astronomer Ralf Vandebergh show a small thin structure trailing the spacecraft, which he suggested may be the parachute, although others disagree.
But even if the spacecraft does have a parachute, it's unlikely to slow the descent, which could be around 250 km per hour.
At that speed the probe is going so fast it will be hard to see and the fireball it produces is unlikely to be spectacular, according to Aerospace's Mr Sorge.
"You're not getting a cloud of shrapnel that's falling down," he said.
"It's just a cannonball."
