An X-shaped object whizzing through space at 17,700km/h is believed to be the debris left behind after two asteroids collided.
Scientists believe the object — nicknamed P/2010 A2 — is from the same cluster of space rocks that killed off the dinosaurs some 65 million years ago.
If the collision theory proves to be true it will be the first time the remnants of an asteroid smash have been seen by humankind — even though astronomers say collisions happen all the time.
The Hubble Space Telescope photographed P/2010 A2, which orbits in the asteroid belt between Mars and Jupiter, earlier last week.
"What Hubble saw indicates that P/2010 A2 is unlike any object ever seen before," astrophysicist Dr Robert Nemiroff from the NASA Goddard Space Flight Centre told The Sun newspaper.
"At first glance, the object appears to have the tail of a comet ... close inspection, however, shows a 140m nucleus offset from the tail centre, very unusual structure near the nucleus, and no discernable gas in the tail."
Scientist David Jewitt from the University of California told Reuters: "The truth is we're still struggling to understand what this means."
Experts say the orbit of P/2010 A2 is related to a group of asteroids known as the "Flora family", which produced the same asteroid that killed off the dinosaurs.
NASA described the object as "comet-like" but pointed out it is different because there is no gas in its trail.
The object was travelling 144 million kilometres from earth.
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