A new assessment of a remotely risky asteroid brings good news: It’s even less threatening than astronomers feared.
The odds of an asteroid dubbed 1950 DA crashing into Earth were still tiny and long into the future: In 2015, scientists calculated that the object had a 1 in 8,000 chance of impacting Earth within a year. 2880. But a new analysis released on Tuesday (March 29) knocks the asteroid off the top spot on NASA’s list of known asteroids that are most potentially dangerous to Earth.
“1950 DA should not be of concern,” Davide Farnocchia, a navigation engineer at NASA’s Jet Propulsion Laboratory in California, told Space.com in an email. “Rather, I would say it’s encouraging that we can identify the remote possibility of an impact for this object more than 800 years in advance.”
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The space rock is 1.3 kilometers wide, and scientists have a pretty good idea of its shape thanks to observations from the old Arecibo Observatory in Puerto Rico. Modeling previously suggested the asteroid was more rubble than rock, which would defuse any possible impact.
Fortunately, the new assessment indicates that the asteroid poses even less of a risk than previously thought. “The probability of impact is miniscule, 1 in 30,000,” Farnocchia wrote of the asteroid, a substantial improvement over previous probabilities. “But even in the very unlikely event that 1950 DA is on an impact trajectory, the possible impact is at 2880 and that leaves plenty of time for mitigation,” he added.
NASA’s mandate includes searching for and monitoring asteroids like 1950 DA through partner telescopes and space observations, coordinated by the agency’s Planetary Defense Coordination Office. There are no imminent threats to fear now, but NASA periodically revisits old assessments to ensure they are accurate.
In January, the agency updated its Sentry system to look at the asteroid risk. Notable changes included better predictions for the Yarkovsky Effect or changes to an asteroid’s path through space due to the sun’s heating.
The effect has a particularly strong influence on the 1950 DA orbit, and for years NASA had calculated asteroid trajectories using a 2002 program called Sentry that could not account for the Yarkovsky effect.
Instead, Farnocchia and his colleagues would have to simulate a large number of scenarios in what he called “a somewhat brutal approach”. Then the scientists had to directly analyze the results to identify possible impacts and probabilities.
So when scientists got new observations from 1950 DA, they didn’t bother to rerun the impact hazards.
However, the new system, called Sentry-II, can account for the Yarkovsky Effect, allowing it to automatically calculate impact risks without all the extra work, so 1950 DA got its first new rating since 2015. Rescanning with Sentry-II only took a few hours, was processed automatically, and will be repeated more regularly.
The lower risk rating moved 1950 DA to second place on NASA’s watch list. Now the top spot goes to Bennu, the asteroid that NASA’s OSIRIS-REx mission sampled in October 2020. The spacecraft will deliver its samples through 2023, giving scientists a detailed look at the rock and, not by chance, helping them assess whether the asteroid poses a threat to the opening of a window in the year 2178.
Editor’s Note: This story has been updated to correct a typo in an instance of 1950 DA. Reporting provided by Space.com Senior Writer Meghan Bartels. Follow Elizabeth Howell on Twitter @howellspace. Follow us on twitter @Spacedotcom and on Facebook.