Near infrared observations of the impacts of seven fragments of Comet Shoemaker-Levy 9 with Jupiter show that precursor flashes are ubiquitous and associated with phenomena at or near the time of atmospheric entry. The comet fragments appear to be a heterogenous group: some impacts produced anomalously bright precursors, while others were completely undetectable despite expectations based on pre-collision images. Strong CO emissions in spectra taken near maximum light point to hot molecular gas which cools within minutes. Finally, images of the disk of Jupiter in the two months after the collision show spreading of the impact structures at approximately 1.5¿ per day. ¿ American Geophysical Union 1995