February is maybe not the best period of the year to dive in a lake, especially a Northern hemisphere one like the Lake Michigan. But courageous (or robot equipped) people may find some interest in such a challenge today!

alerts-imo
Map of witnesses that reported the February 6th, 2017 fireball (IMO event #454-2017). Credit: IMO, AMS.

On February 6th, 2017, around 07h 27min UT (ie 01:27 am CST), a very bright greenish fireball was widely observed, heard (by 23% of witnesses) and filmed: more than 450 people have reported it so far! Such reports comes from all states South of the Great Lakes regions: mainly Wisconsin and Illinois, but the event was also visible from Minnesota, Iowa, Northen Missouri, North-Eastern Kansas, Indiana, Ohio, Northern Kentucky, Michigan, Northern, New York state, and Ontario (Canada). Reports and videos described a very bright green medium speed fireball that lasted around 4.5 seconds and underwent multiple final light bursts before disappearing.

From automatic analysis of visual reports, the luminous path of the fireball started upright of a surface point located between Boltonville and Fillmore (Washington County, WI), and disappeared 20 km offshore Manitowoc (Manitowoc County, WI), around 40 km altitude, above the Michigan Lake. This trajectory seems to be highly confirmed by NOAA’s NEXRAD Doppler Weather Radar recordings of the NOAA, which shows a radar echo near the end of the meteoroid atmospheric trajectory deduced from visual observations. Which unfortunately means that potential residual meteorites, if any, must currently lay at the bottom of Lake Michigan, where the floor is the deepest (more than 250 m depths)…

NASA's NEXRAD Doppler Weather Radar echo of the February 6th, 2017 fireball. Echoes on top of the map are due to rain, but the patch above the Lake Michigan is linked to the ionized train of the bright meteor. Credit: Marc Fries, NOAA
NASA’s NEXRAD Doppler Weather Radar echo of the February 6th, 2017 fireball. Echoes on top of the map are due to rain, but the patch above the Lake Michigan is linked to the ionized train of the bright meteor. Credit: Marc Fries, NOAA

Other videos of the event:

UPDATE (09/02/2017): Mass of the small asteroid that illuminated the Wisconsin skies on February 6th seems to have ranged between 1 and 7 tons (thus a few meters wide, which is the size of a small van), meaning its energy was equal to about 500 tons of TNT.

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