The object, known as P/2010 A2, was circling about 90 million miles (144 million km) from Earth in the main asteroid belt between Mars and Jupiter when it was spotted last week by the Hubble Space Telescope.
"The truth is we're still struggling to understand what this means," lead scientist David Jewitt with the University of California at Los Angeles, told Reuters on Tuesday. "It's most likely the result of a recent collision between two asteroids."
If so, he said, "It'd be the first case we've seen of an asteroid smash happening, basically caught in the act."
The object resembles a comet, but its nucleus is severed from its tail, which "has a very strange appearance, the likes of which we've never seen before," Jewitt said.
Studies of the object -- and searches for similar ones -- would improve scientists' understanding of how asteroids break apart, information that may be useful to thwart a future asteroid strike on Earth.
"The thing that we want to understand is how the asteroids smash into each other and destroy each other," Jewett said. "It might help us understand even how to destroy an asteroid and prevent one from hitting us."
Scientists believe a giant comet or asteroid that hit Earth about 65 million years ago was linked to the extinction of the dinosaurs, possibly by throwing up dust or chemical clouds that blocked the sun or by igniting global wildfires.
Calculations show the orbit of P/2010 A2 is related to the group of asteroids, known at the Flora family, that produced that asteroid.
NASA is working to catalog at least 90 percent of the estimated 1,000 objects that approach Earth and are larger across than one kilometer, about two-thirds of a mile. The agency's proposed budget for the year beginning October 1 includes a $16 million annual increase to step up that effort. (Reuters)