Canberra team will 'take another look' at Earth-shattering asteroid in 2028

Crisis averted – it’s looking extremely unlikely Asteroid 2024 YR4 is on a collision course with Earth.

Initially, there were fears the 55-metre ball of rock – weighing tens of thousands of tonnes and currently hurtling through space at 10 times the speed of a rifle bullet – would explode over the Southern Hemisphere on 22 December 2032 with the force of eight mega-tonnes of TNT.

The maths now pegs it at a 0.0017 per cent chance this will happen, with a greater chance of 1.7 per cent it will hit the moon instead.

And we know all this, in part due to the work of the ‘Space’ team here at UNSW Canberra, joined by Dr Ed Kruzins.

Dr Kruzins was the previous CSIRO Director of NASA Operations and the Canberra Deep Space Communications Complex (CDSCC) at Tidbinbilla until February 2021, when he became Professor of Practice at UNSW Canberra Space.

The group is the founding member of the Southern Hemisphere Asteroid Research Consortium (SHARC), which also involves Tidbinbilla, the Parkes Telescope and the Australia Telescope Compact Array (ATCA) in Narrabri in NSW, and monitors asteroids on behalf of NASA.

“I created the program in 2015 because our NASA colleagues were saying how there’s no one looking from the Southern Hemisphere up at these asteroids and how there’s a gap and how we should do something about it,” Dr Kruzins says.

So far, more than seven students have come through the program through the neighbouring Australian Defence Force Academy (ADFA). And it’s even blossomed into relationships with the University of Tasmania and the University of Western Australia.

It’s called a “biostatic radar program”, which illuminates the asteroids with high-energy radio frequency waves from the big antennae at Tidbinbilla, which bounce off the asteroid and are received by either Parkes or Narrabri.

“We then analyse the data which tells you whereabouts it is in the sky, so we can precisely determine its orbit. It’ll tell you rotational rates, polarisation ratios, surface roughness – all these things that tell you the characteristics of the asteroid,” he says.

The university’s two optical telescopes, one based at Duntroon and the other in Yass, then provide visual information.

From all of this, NASA upgrades or downgrades the asteroid warnings.

“We only look at asteroids with a potential threat to Earth,” Dr Kruzins says.

“A lot of asteroids are just bags of sand held together by gravity, and this one looks very similar to that. It would probably break up in the atmosphere, but that energy still gets dissipated as an air burst, so it’d be a huge thermal release as well as a sonic blast.

“That would be sufficient for flattening buildings.”

As many as 10 to 20 asteroids pepper the Earth’s atmosphere every year, but the likes of Asteroid 2024 YR4 are much rarer.

An asteroid 10 metres and above can be statistically expected to arrive every 10 years or so, with enough power to break windows and flatten small areas of forests, while those over 100 metres wide will hit the Earth approximately every 5000 years.

“The last time you saw anything like 2024 YR4 was in 2012, in Chelyabinsk in Russia, when a 10 to 20-metre asteroid – about a quarter of the size of this – lit up the whole sky at night and smashed windows from the sonic boom,” he says.

While a few people were injured by the breaking glass in Russia, there was no structural damage to buildings. But Asteroid 2024 YR4 would be different.

Geometry calculations suggested it would explode over a broad patch between South America, Africa and India – in other words, potentially right over us here in Australia.

But Dr Kruzins says there’s a greater chance we’ll be treated to a “spectacular show” on the moon instead.

“It would land in one bit because there’s no atmosphere to break it up, so … it would punch a crater there, and you’d see a lot of light coming out of it if we were in the right orientation.”

For now, the asteroid has plunged out of sight of the Southern Hemisphere’s telescopes and isn’t expected to come back around until 2028.

“We’ll have another look then.”