Back to main Impact Risk Page. 2004 MN4
Earth Impact Risk Summary Torino Scale (maximum) 1 Palermo Scale (maximum) -2.00 Palermo Scale (cumulative) -2.00 Impact Probability (cumulative) 3.7e-05 Number of Potential Impacts 4 V impact 12.59 km/s V infinity 5.86 km/s H 19.6 Diameter 0.410 km Mass 9.5e+10 kg Energy 1.8e+03 MT all above are mean values
weighted by impact probability Analysis based on
147 observations spanning 288.92 days
(2004-Mar-15.1104 to 2004-Dec-29.02821) Orbit diagram and elements available here.
These results were computed on Dec 29, 2004
2004 MN4
Earth Impact Table Date Distance Width Sigma
Impact Sigma
LOV Stretch
LOV Impact
Probability Impact
Energy Palermo
Scale Torino
Scale YYYY-MM-DD.DD (r Earth ) (r Earth ) (r Earth ) (MT) 2044-04-13.29 0.74 7.56e-03 0.000 -3.42084 1.68e+04 1.3e-07 1.79e+03 -4.35 0 2045-04-13.62 0.99 6.04e-03 0.000 -2.95368 1.76e+04 1.2e-07 1.78e+03 -4.40 0 2053-04-13.51 0.60 8.86e-03 0.000 -0.39284 1.73e+04 3.6e-05 1.78e+03 -2.00 1 2087-04-13.73 0.76 1.20e-03 0.000 3.53782 6.15e+04 1.7e-08 1.78e+03 -5.57 0
Summary Table Description The Summary Table includes basic information about the hazard for this object. The maximum Torino and Palermo Scale values are listed, as well as the number of tabulated potential impacts and their corresponding cumulative Palermo Scale value and cumulative impact probability. The observation set used for the analysis is also listed. Certain parameter values depend upon the specific impact event in question, but they change little among the various table entries. For this reason we tabulate only mean values for these parameters: V impact - Velocity at atmospheric entry.
- Velocity at atmospheric entry. V infinity - Relative velocity at atmospheric entry neglecting the acceleration caused by the Earth's gravity field, often called the hyperbolic excess velocity. (V infinity 2 = V impact 2 - V escape 2 , where V escape = ~11.2 km/s is the Earth escape velocity.)
- Relative velocity at atmospheric entry neglecting the acceleration caused by the Earth's gravity field, often called the hyperbolic excess velocity. (V = V - V , where V = ~11.2 km/s is the Earth escape velocity.) H - Absolute Magnitude, a measure of the intrinsic brightness of the object.
- Absolute Magnitude, a measure of the intrinsic brightness of the object. Diameter - This is an estimate, based on the absolute magnitude, and assuming a uniform spherical body with visual albedo p V = 0.154. Since the albedo is rarely well determined the diameter estimate should be considered quite rough, but in most cases will be accurate to within a factor of two.
- This is an estimate, based on the absolute magnitude, and assuming a uniform spherical body with visual albedo = 0.154. Since the albedo is rarely well determined the diameter estimate should be considered quite rough, but in most cases will be accurate to within a factor of two. Mass - This estimate assumes a uniform spherical body with the computed diameter and a mass density of 2.6 g/cm 3 . The mass estimate is somewhat more rough than the diameter estimate, but generally will be accurate to within a factor of three.
- This estimate assumes a uniform spherical body with the computed diameter and a mass density of 2.6 g/cm . The mass estimate is somewhat more rough than the diameter estimate, but generally will be accurate to within a factor of three. Energy - The kinetic energy at impact: 0.5 * Mass * V impact 2. Measured in Megatons of TNT.
Impact Table Legend See our Introduction for a more extensive explanation of these terms. Date The calendar date (UTC) of the potential impact.
Distance The minimum distance on the target plane (scaled b-plane) from the LOV to the geocenter, measured in Earth radii. For these purposes the radius of the Earth, 6420 km, includes some allowance for the thickness of the atmosphere.
Width The one-sigma semi-width of the LOV uncertainty region, measured in Earth radii.
Sigma Impact The lateral distance in sigmas from the LOV to the Earth's atmosphere. Zero indicates that the LOV intersects the Earth. It is computed from (Distance - 1)/Width.
Sigma LOV The coordinate along the Line Of Variations (LOV). This value is a measure of how well the impacting orbit fits the available observations. Zero indicates the best-fitting, central (nominal) orbit and the further from zero, the less likely the event: Roughly 99% of all the uncertainty region lies between -3 and +3. Sentry explores out to Sigma LOV = +/-5.
Stretch LOV The stretching is the semimajor axis of the local linear uncertainty region. It describes how fast one moves across the target plane as Sigma LOV changes, and is measured in Earth radii per sigma. The local probability density varies inversely with the stretching, and thus larger stretching values will generally lead to lower impact probabilities.
Impact Probability The probability that the tabulated impact will occur. The probability computation is complex and depends on a number of assumptions that are difficult to verify. For these reasons the stated probability can easily be inaccurate by a factor of a few, and occasionally by a factor of ten or more.
Impact Energy The kinetic energy at impact, based upon the computed absolute magnitude and impact velocity for the particular case, and computed in accordance with the guidelines stated for the Palermo Technical Scale. Uncertainty in this value is dominated by mass uncertainty and the stated value will generally be good to within a factor of three.
Palermo Scale The hazard rating according to the Palermo Technical Impact Hazard Scale, based on the tabulated impact date, impact probability and impact energy.
Torino Scale The hazard rating according to the Torino Impact Hazard Scale, based on the tabulated impact probability and impact energy.
NASA's Near Earch Object Program Office has recently announced that the asteroid named 2004 MN4, discovered last June, has the highest risk of earth impact to date. In the December 23 annoncement, NASA advised that the 400-meter wide asteroid has a 1 in 300 chance of colliding with earth.  As scientists gather more data on 2004 MN4, the probability of collision with earth is expected to decrease.

The level of impact risk is measured in terms of Torino Impact Hazard Scale, and the MN4's score was initially 2 out of 10. 2004 MN4 is expected to come closest to the Earth on April 14, 2029.