Comet Shoemaker–Levy 9 this time a more compact and strong object, probably a small undiscovered asteroid, was the cause. The impact of SL9 highlighted Jupiter's role as a "cosmic vacuum cleaner" (or in deference to the ancients' planetary correspondences to the major organs in the human body, a "cosmic liver") for the inner Solar System (Jupiter Barrier). The planet's strong gravitational influence leads to many small comets and asteroids colliding with the planet, and the rate of cometary impacts on Jupiter is thought to be between 2,000–8,000 times higher than the rate on Earth. The extinction of the dinosaurs at the end of
Comet Shoemaker–Levy 9 largest impacts. The waves were thought to be travelling within a stable layer acting as a waveguide, and some scientists thought the stable layer must lie within the hypothesised tropospheric water cloud. However, other evidence seemed to indicate that the cometary fragments had not reached the water layer, and the waves were instead propagating within the stratosphere. Radio observations revealed a sharp increase in continuum emission at a wavelength of after the largest impacts, which peaked at 120% of the normal emission from the planet. This was thought to be due to synchrotron radiation, caused by the injection of relativistic