1997 XR2

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1997 XR₂ (also written 1997 XR2) is an asteroid discovered in 1997. 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, 1997 XR₂ 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 NEO to be ranked higher than zero (the scale is 0–10) until it was joined by 2004 VD₁₇ at level one in November 2004, and then when 99942 Apophis (then known only by its provisional designation 2004 MN₄) was temporarily assessed at level four in December 2004. Currently 2004 VD₁₇ and 99942 Apophis are rated at level zero (as of February 2007).

On February 24, 2006, 1997 XR₂ 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.

[edit] References

• NASA Near Earth Object Program. "Current Impact Risks" http://neo.jpl.nasa.gov/risk/ (accessed 30 Sep. 2005).
• Ibid. "1997 XR₂ 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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