Momma always said to pick up after yourself. Otherwise, you won’t know where your old pieces of junk will end up, and might end up confusing them with asteroids.

Astronomers have decided that a near-Earth object that passed by Earth last week is likely a rocket piece, a chunk of metal left behind in the darkness of space while some orbiter or NASA explorer zoomed off on an exciting mission.

Richard Kowalski at the Catalina Sky Survey discovered “2010 KQ,” a few-meter-wide something or other, headed for Earth on May 16. Tracked by NASA’s Near-Earth Object Observations Program, commonly called “Spaceguard,” the something made a relatively close pass to our planet (it was just a bit further out than the moon’s orbit) on May 21. Yesterday, NASA announced that the object was likely the upper-stage of a rocket.

Why the confusion? First, using spectral analysis, astronomers could see that the object’s makeup was not like any known asteroid. Second, the folks at NASA were suspicious of the object’s path, which looked a lot like our own planet’s orbit around the sun. Things that start moving with us, unless overcome by gravity or propelled by rockets, tend to want keep on going the same way.

“The orbit of this object is very similar to that of the Earth, and one would not expect an object to remain in this type of orbit for very long,” said Paul Chodas, a scientist at NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif. [NASA]

This isn’t the first such asteroid identity crisis. Astronomers had a similar mix-up regarding 2010 AL30, which made a pass by Earth in January of this year. Scientists debated whether it was a piece of the Venus Express spacecraft, but decided to define it as a “Apollo class” asteroid. You can look at its orbit here.

Astronomers expect for 2010 KQ to visit our neighborhood again in 2036, but there is only a six percent chance that it will actually hit us. Even if it does, it will completely burn up in our atmosphere/trash incinerator.

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Image:  NASA/JPL