For the first time ever a meteor / Near Earth Object (NEO)(Is it the one? 
:-)) has been detected that ranks as category
2 on the Torino seriousness scale. Till now 2 have rated category 1 and many
more category 0.

    http://neo.jpl.nasa.gov/risk/

0 means, essentially ignore it.

1 means "merits careful monitoring"

2 means "merits more than .... " :-)

Object MN42029 will have a POTENTIAL for earth impact 28 times over the
years 2029 - 2079 with a cumulative probability of impact of 4.3E-3 (0.43%)
over this period.

Speed of initial approach before gravitation of various bodies starts to
play with it is very small for such objects at only 5.85 km/s  (21,000 kph).
Estimated diameter is 420 metre, which is very small compared to eg "the
dinosaur killer" (which may have been no such thing) but large compared to
your average H bomb. As a guide to size, the 1.2 km diameter "Barringer
crater" / "Meteor Crater" in Arizona is believed to have been made by a 30
to 50m diameter iron meteorite. The new object is 400/50 = 8 times as large
across so at the same velocity and material would have 8^3 = 500 times the
energy. Barringer was quite possibly faster than the newcomer's current
velocity. Not in the same class as  Chicxulub, fortunately.

A nice collection of information on and pictures of terrestrial impact
craters

        http://www.solarviews.com/eng/tercrate.htm




        RM

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