1997 XR2

mp|1997 XR|2 (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, mp|1997 XR|2 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 mpl|2004 VD|17 at level one in November 2004, and then when 99942 Apophis (then known only by its provisional designation mp|2004 MN|4) was temporarily assessed at level four in December 2004. Currently mpl|2004 VD|17 and 99942 Apophis are rated at level zero (as of February 2007).

On February 24, 2006, mp|1997 XR|2 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." "mp|1997 XR|2 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).