What to do
Alan Harris, of the Space Science Institute in Boulder, CO, saw Stoss' message and checked the orbit path posted on the Minor Planet Center web site, which all the astronomers knew was preliminary and could have wide error margins. Harris realized that the orbit path posted would have the asteroid, considered a Near Earth Object (NEO), hitting Earth the next day.
At 7:09 p.m. EST, Harris alerted several colleagues, including Don Yeomans, head of the Near Earth Object Program Office at NASA's Jet Propulsion Laboratory (JPL).
Yeomans called the Minor Planet Center to try and get access to the original data set (the actual observations are not posted on the Minor Planet Center web site until after an official announcement circular is published, usually in a couple days). Spahr, not realizing he'd posted an orbital path that went right through the Earth, had gone to dinner.
It took about 30 minutes before Yeomans and his colleagues heard back from Brian Marsden, director of the Minor Planet Center, who was working late that evening. After another 20 minutes, Yeomans and his JPL team had the observational data and calculated the rock had about a 25 percent chance of impact.
Meanwhile, other possible paths based on the sketchy data showed the rock could also miss Earth be a wide margin. More observations were needed.
Clark Chapman of the Southwest Research Institute, also in Boulder, had been apprised of the situation, too.
"As I was driving home, I was thinking that this must be a mistake," Chapman recalled last week. Asteroid experts have seen many threats of impacts, predicted for future years, come and go over the course of a day or two as new observations provided a more accurate picture of a space rock's path. Never, however, have they faced such an apparently imminent threat.
Chapman had begun keeping a narrative of the unusual situation. At one point early on, this log included musings over whether NASA or the White House should be alerted, but he says it was not something he seriously contemplated.
Many in the media reported that the astronomers had pondered calling the White House. Chapman says the media got it wrong.
During the critical period when JPL had calculated a 10 to 40 percent chance of impact, "there's nothing in the narrative that says a thing about the White House," Chapman said. He and NASA's David Morrison, who was also involved in the e-mail communications, both say there was never any serious consideration of calling the president.
"The real issue that we did discuss was when, if at all, it would be appropriate for any of us, especially Don Yeomans to notify officials in the Office of Space Science at NASA Headquarters," Morrison said, adding that he did wonder who should be called if it became necessary.
Hours passed as cloudy skies prevented follow-up observations.
Finally, in the wee hours of Jan. 14, the spot where AL00667 would have been if it were heading earthward was found to be empty. (The object was later calculated to be larger, and computers showed it would come nowhere close to Earth. It was then given a permanent designation of 2004 AS1.)
