- 1997 XR2
mp|1997 XR|2 (also written 1997 XR2) is an
asteroid discovered in1997 . It has a diameter of 0.1-0.3 km and an estimated mass on the order of 1010 kilograms.From early
2002 toFebruary 24 ,2006 , mp|1997 XR|2 was considered to have about a 1 in 10,000 chance of colliding withEarth onJune 1 ,2101 , based on 144 observations going back to December of1997 .It was ranked a one on the
Torino Scale of impact risk, and was the onlyNEO to be ranked higher than zero (the scale is 0–10) until it was joined by mpl|2004 VD|17 at level one in November2004 , and then when99942 Apophis (then known only by itsprovisional designation mp|2004 MN|4) was temporarily assessed at level four in December2004 . 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).
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