[JohnG45]

... this was not an object of ours. Instead, 2006 RH120, as it became known, turned out to be a tiny asteroid just a few metres across--a natural satellite like the Moon. It was captured by Earth's gravity in September 2006 and orbited us until June 2007 when it wandered off into the Solar System in search of a more interesting neighbour.

Captured and released? How exactly did it get "released" to wander off in search of a more interesting neighbor?

[bigheadfred]

It didn’t exactly get released. It just left in disgust.

[coloradan]

It’s all the moon’s fault. Without the moon, something not already in Earth orbit can only come by parabolically or hyperbolically (some which crash into the Earth). But a deflection by the moon can put it into a stable orbit, at least until the moon kicks it out again. Which it is likely to do, given how many other moons we have besides the main one, accumulated over billions of years of moon collection time.

[Lonesome in Massachussets]

It was only ever weakly gravitationally bound to earth. An asteroid orbiting the sun in the same direction as the earth and the other planets can be captured by a planet when it's orbit crosses near the orbit of the planet in front of the direction in which the planet is orbiting the sun. The gravitational attraction drags the asteroid towards the planet (and the planet slightly towards the asteroid). The orbital velocity of the asteroid decreases and it can be kept in orbit around the planet. The amount of deceleration experienced by the asteroid determines how tightly it is bound to the planet.

The any object orbiting a planet is perturbed by the gravity of every other particle in the solar system. For objects orbiting the earth, the significant perturbing bodies are, more or less in order: the moon, the sun, Venus and Jupiter. Depending on their relative locations, they can provide just enough of a push to free a weakly bound object from the grasp of earth's gravity and continue in orbit around the sun.

Jupiter, of course is the king of capture, remember Shoemaker-Levy? It was captured in 1968, but not observed until 1994, shortly before its perturbed orbit caused it to collide with Jupiter.

The opposite of capture occurs, too. An asteroid approaching a planet's orbit from behind can be given a boost that increases its velocity enough to hurl it out of the solar system. Numerous solar system missions take advantage of the gravitational boost available from Jupiter and the other planets.

[calex59]

Captured and released? How exactly did it get "released" to wander off in search of a more interesting neighbor?

My thoughts exactly. Does it have it's own source of power, if not how did it move out of our gravity field. If it does, how did it get that source of power and is it man made?

[COBOL2Java]

Captured and released? How exactly did it get "released" to wander off in search of a more interesting neighbor?

It must have crossed the border from Mexico.