Quote:

---

A small asteroid passed within the moon's distance from the Earth on Wednesday morning, and another will do likewise later in the day, space watchers say.

The double encounter is an unusual event that shows the need for closer monitoring of near space for Earth-threatening encounters, according to NASA.

The objects don't pose a threat to Earth, and they will not be visible to the naked eye, said Donald Yeomans, manager of NASA's Near Earth Program, which tracks potentially hazardous asteroids and comets within 28 million miles of Earth.

Roughly 50 million objects pass through near-Earth space each day, Yeomans said. But what makes this situation noteworthy is that these two asteroids are passing so close to Earth on the same day and that NASA spotted them so far in advance.

"Things like this happen every day that we simply don't know about because we don't have the telescopes large enough to find them or surveys that are looking full-time," he said. "This demonstrates the system's working on some level, but we need larger telescopes and more of them to find objects that are coming this close."

Yeomans described the discovery as a warning shot in a field of study of low-probability events with global, high-impact consequences. He said that it was only when scientists began looking for near-Earth objects in the 1990s that they realized there was a "problem."

"We have only recently appreciated how many of these objects are in near Earth's space and [it's] best that we keep track of them and find them," he said. "I think this is Mother Nature's way of firing a shot over the bow and warning Earth-based astronomers that we have a lot of work to do."

---