However, more recent and further refined calculations based on both new and archival data indicate that the closest approach will be 600,000 miles in 2028. Shown to the same scale from left to right are Mathilde , Gaspra , and Ida . Mathilde has dimensions of about 37 by 29 miles. The asteroid 1997 XF11 is much smaller, probably a mile wide, yet the impact of an asteroid of this size could have catastrophic effects . Over the last two decades, teams of astronomers have just begun to catalog and track near-earth objects .
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