Scientists have identified a thousand-yard-wide (one-kilometer-wide) asteroid that may be heading for a collision with Earth—878 years from now.

Using radar and optical measurements made over the past 51 years, researchers have calculated that there is up to a one-in-300 possibility that Asteroid 1950 DA will slam into Earth on March 16, 2880. Their work is published in the April 5 issue of Science.

"We calculated the probability of collision based on what we know about the physical aspects of the asteroid and many other factors," said Jon Giorgini of NASA's Jet Propulsion Laboratory at the California Institute of Technology in Pasadena. "As we get more information we will be able to adjust the level of probability up or down."

Odds of one in 300 may seem almost insignificant, but it is the highest Earth-impact potential ever assigned by scientists to an object in space, according to Giorgini.

The consequences of a collision from an asteroid a thousand yards in diameter are speculative. Could a direct hit destroy an entire city? Would an ocean impact create a massive tsunami capable of deluging adjacent coast lines?

"Nothing good can come from such an impact," said Giorgini. "But a collision between 1950 DA and Earth is so unlikely it is not worth worrying about. And even if it does look like there could be a collision, we have plenty of time and many ways to deflect the asteroid from its path."

Changing the Trajectory

One of the easiest ways to deflect the asteroid past Earth would be to alter its surface, changing the amount of heat energy it radiates, said Joseph Spitale, a research associate in planetary science at the University of Arizona–Tucson. That would have the effect of subtly altering the way the asteroid moves, causing it to slowly change its trajectory.

In a separate paper published in Science, Spitale describes how the so-called Yarkovsky Effect could be used to make an asteroid drift off its path. The Yarkovsky Effect is a term used to describe how an asteroid's trajectory can be influenced by its heat radiation.

"The thermal emission from an asteroid acts like a rocket force in the opposite direction, although it is really, really weak," Spitale said. "If we can somehow change the thermal radiation being emitted by an asteroid, we can affect the object's orbit. A tiny thrust acting over a long time can be enough to nudge an asteroid from a path heading towards the Earth to one that narrowly misses the Earth."

Because the Yarkovsky Effect is completely determined by temperatures on the surface of a body, Spitale explained, it can be manipulated if the surface can be altered in a way that changes that temperature distribution.

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SOURCES AND RELATED WEB SITES NASA Jet Propulsion Laboratory Science magazine University of Arizona–Tucson Lunar and Planetary Laboratory