(also written 1997 XR2) is an asteroid discovered on December 4, 1997.^[1] It has a diameter of 0.1-0.3 km and an estimated mass on the order of 10¹⁰ kilograms.

From early 2002 to February 24, 2006, was considered to have about a 1 in 10,000 chance of colliding with Earth on June 1, 2101, based on 144 observations going back to December of 1997.

It was ranked a one on the Torino Scale of impact risk, and was the only near-Earth object to be ranked higher than zero (the scale is 0 10) until it was joined by at level one in November 2004, and then when 99942 Apophis (then known only by its provisional designation ) was temporarily assessed at level four in December 2004. Currently and 99942 Apophis are rated at level zero (as of February 2007).

On February 24, 2006, was observed by the Mt. Lemmon Survey after being lost for more than 8 years. The refinement of its orbit eliminated the possibility of impact in 2101.

References

• NASA Near Earth Object Program. "Current Impact Risks" http://neo.jpl.nasa.gov/risk/ (accessed 30 Sep. 2005).
• Ibid. " Earth Impact Risk Summary" (29 May 2002). http://neo.jpl.nasa.gov/risk/1997xr2.html (accessed 3 Apr. 2004).
• Asteroid/Comet Connection. "Consolidated Risk Tables" http://www.hohmanntransfer.com/crt.htm#news (accessed 25 Feb. 2006).

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