(CBS News) -- An asteroid gaining notoriety for its potential to collide with Earth in 2032 was estimated Tuesday to have roughly a 3% chance of striking our planet -- the highest probability ever assigned -- before additional analysis Wednesday lowered the chances to about 1.5%, according to NASA's Center for Near-Earth Object Studies.
Risks of the massive space rock -- which falls into the "city killer" category -- actually making impact have fluctuated since it was first discovered last December. Called 2024 YR4, the near-Earth asteroid initially carried a 1% chance of hitting land when NASA and the European Space Agency first announced its existence last month.
Protocols require the agencies to formally notify the public when the odds of an asteroid strike reach that 1% threshold, which in itself is an extremely rare occurrence.
The highest estimate, by NASA's Jet Propulsion Laboratory, suggested a 3.1% chance the asteroid will hit Earth on Dec. 22, 2032, during a fleeting window of time in which the rock's orbit around the sun intersects the path of the planet. That would make the odds of a collision still quite small, about 1 in 32.
The European Space Agency's latest probability estimate was slightly lower, at 2.8%. Last week, NASA and the ESA agreed the probability of an asteroid strike was closer to 2%.
"However," NASA reported, "on Wednesday, Feb. 19, new data collected overnight reduced the impact probability to 1.5%."
It added, "NASA expects the impact probability to continue to evolve as new observations of asteroid 2024 YR4 are made over the coming days and weeks."