WASHINGTON - Thousands of asteroids as big as the Washington Monument zip around our solar system at 64,000 kmh, hunks of metal or rock that could strike with 10 times the force of the most powerful nuclear weapon and kill millions of people.
Congress wants Nasa to find them. The Biden administration says it can wait.
The space agency estimates there are about 25,000 asteroids of at least 140m in diameter near Earth's orbit. While the odds of them crashing into our planet at any given time are minuscule, Congress directed Nasa to find 90 per cent of them by 2020.
Scientists have found fewer than half. But for reasons it has not publicly explained, the administration has proposed delaying by two years, until 2028, the launch of an infrared space telescope meant to find those threatening asteroids and sharply cutting its budget for next year.
One space policy advocate called the move "baffling".
Lawmakers have pushed back, inserting measures into key Bills and calling for a faster timeline for the telescope's funding and launch.
The fight could flare up as the federal government's Sept 30 shutdown deadline approaches. It also comes as Nasa focuses on higher-profile missions. Artemis 1, an uncrewed Moon-orbiting mission, is slated to launch Saturday, while a separate mission to collect rock and dust samples from Mars is looming.
On Sept 26, Nasa also plans to direct a spacecraft the size of a small car to slam into an asteroid at 24,000 kmh in a bid to shift its trajectory. That asteroid isn't a threat to Earth, but the mission is the first time Nasa has practised bumping one to change its course.
'We can't act on what we can't see'
Asteroid-ramming techniques won't matter if scientists can't find the potential threats, advocates say.
"You can't mitigate anything unless you know it's there," said Professor Amy Mainzer, of the University of Arizona and mission director for the Near Earth Object Surveyor, the telescope being put on hold.
"We know from experience that it takes time to build and launch spacecraft. So, every year that we wait - that we don't have a good understanding of what is out there - is a year that basically makes it less likely for us to go mitigate something if we did find something," she said.
About 500 times a year, researchers identify asteroids of at least 140m in diameter near Earth's orbit. At that size - the width of one-and-a-half football fields - they pass a semi-apocalyptic Goldilocks test.
They're not quite as big as the 10km to 15km asteroid that led to the extinction of the dinosaurs, but there's more of them and they're harder to find. And they're much more destructive than the asteroids of 20m or less that more frequently hit Earth.
Smaller but no less terrible
A study published in 2019 by the National Academies of Sciences, Engineering and Medicine concluded a 140m asteroid could release the equivalent of 500 megatons of TNT upon impact. That's more than 30,000 times as powerful as the atom bomb the US dropped on Hiroshima.
Such asteroid strikes happen rarely: The same report put the average interval between them at 20,000 years. Much more frequently, Earth gets the smaller variety space objects that leave their own trail of destruction.
In 2013, a roughly 20m asteroid broke apart about 25km above the town of Chelyabinsk, Russia, shattering windows and injuring more than 1,600 people. Russia also was the site of the most destructive asteroid in recorded human history.
In 1908, a 50m to 80m asteroid struck near the Podkamennaya Tunguska River and flattened more than 2,000 sq km of uninhabited forest.
For now, Nasa is still mostly reliant on ground-based observations to spot objects of 140m or more. Officials also repurposed a space telescope, called Neowise, that was originally meant to find planets - but it's only discovered five large asteroids this year.
The Surveyor telescope is projected to have a wider field of vision, allowing scientists to get a broader landscape of nearby asteroids, Mr Casey Dreier, chief advocate and senior space policy adviser at the Planetary Society, said in a phone interview. And its infrared sensors will spot dark asteroids invisible to the naked eye.
"They're like these dark, charcoal, potato-like things that are tiny, and you know generally where they could be but don't know where they are," Mr Dreier said. "And if they're moving fast, it's hard to find them at the right time."
Nasa spokesman Joshua Handal said Nasa "will launch NEO Surveyor as early as possible", but did not answer questions about why the administration proposed the delay.
In its annual budget justification, Nasa cited its need to "support other high-priority missions", pointing to "cost growth" for its missions collecting surface samples on Mars and surveying one of Jupiter's moons.
Prof Mainzer said she hasn't gotten an explanation from the administration for the proposed cuts and delay.
In conversations with congressional staff, Nasa has cited the narrow launch windows for the Mars mission as one reason for changing the Surveyor's budget and timetable, a House Republican aide said. If officials miss their deadline to launch the Mars spacecraft, they'll have to wait another 26 months.
The Surveyor doesn't face similar constraints. Mr Dreier described the budget request to Congress - US$39.9 million (S$56 million), rather than the US$170 million that constitutes full funding - as "baffling".
There's no apparent reason Nasa couldn't have simply asked for more money, rather than pitting missions against each other, he said.
By comparison, Congress allocated more than US$170 million in 2022 for the National Gallery of Art, the National Agricultural Statistics Service, and the maintenance of House office buildings.
"It's really a tiny drop in the bucket," Mr Leroy Chiao, a retired Nasa astronaut and commander of the International Space Station, said in a Bloomberg Radio interview. "Any time you're cutting programmes, and satellite programmes - whether it's satellite programmes or human spaceflight programmes - it's kind of a shame," he said. BLOOMBERG