Minimum orbit intersection distance (MOID) is a measure used in astronomy to assess potential close approaches and collision risks between astronomical objects.
[1] A low MOID does not mean that a collision is inevitable as the planets frequently perturb the orbit of small bodies.
MOID has the convenience that it is obtained directly from the orbital elements of the body and no numerical integration into the future is used.
[3] The only object that has ever been rated at 4 on the Torino Scale (since downgraded), the Aten asteroid (99942) Apophis, has an Earth MOID of 0.00026 AU (39,000 km; 24,000 mi).
[4] The first two objects that were detected and had their Earth-MOID calculated before Earth impact were the small asteroids 2008 TC3 and 2014 AA.