Mass and penetration depth of Shoemaker‐Levy 9 fragments from time‐resolved photometry

Computational simulations of the first 100 seconds of interaction of Shoemaker‐Levy 9 fragments with the Jovian atmosphere have revealed a potential method for estimating the masses and penetration depths of the individual objects. For sufficiently large fragments, impact‐generated fireballs will rise into line‐of‐sight over the Jovian limb (less than one minute after impact for a 3‐km diameter fragment). It is possible that time‐resolved radiometric measurements from Earth‐ and orbital‐based observatories may detect two different arrivals for each impact: first the shock wave and, a few seconds later, a debris front (fireball). Measurements of one or both arrival times with time resolutions of better than one second will provide information that would place strong restrictions on the range of values of equivalent explosive yield (from which fragment mass can be extracted) and effective penetration depth. We believe that time‐resolved photometry measurements of impact‐induced light emission (impact‐flash signatures) will provide the best means by which Shoemaker‐Levy 9 fragment masses can be determined if they are greater than about 5×1015 g (corresponding to a 1‐km diameter ice sphere).