In late July, a record-setting asteroid hurtled just 40,400 miles over Earth, the largest space rock to come so close in a century. But perhaps more alarming than the flyby itself is how much it caught NASA by surprise, according to internal agency documents obtained by BuzzFeed News.

Spotted just 24 hours before a relatively narrow miss with Earth, the incident reveals holes in NASA’s surveillance network to observe incoming space rocks. The football-field-sized asteroid, dubbed “2019 OK,” is also drawing attention to decades of congressional failures to fix the problem, experts say.

“Because there may be media coverage tomorrow, I’m alerting you that in about 30 mins a 57-130 meter sized asteroid will pass Earth at only 0.19 lunar distances (~48,000 miles),” wrote Lindley Johnson, NASA’s planetary defense officer, in a July 24 email alert sent to other space agency experts. “2019 OK was spotted about 24 hrs ago.”

Flying at nearly 55,000 miles per hour, the asteroid came lumbering by with little warning, first detected that day by a small observatory in Brazil. The flyby came five times closer to Earth than the distance to the moon — a close shave by astronomical standards.

“If 2019 OK had entered and disrupted in Earth’s atmosphere over land, the blast wave could have created localized devastation to an area roughly 50 miles across,” according to a news release sent out by the agency weeks after the flyby. Such an impact has been estimated to happen about once every 3,000 years.

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