However, in regions of heavy rainstorms or snowstorms, these organisms would have survived the first few hours. Sea creatures would have been buffered from effects in the first hours, but plankton on the surface might have died out over the weeks of darkness, decreasing the food supply for small fish, which affected the bigger fish, and so on. These examples show how hard it is to predict the exact effects of the impact. This may explain why mammals replaced giant reptiles after the impact. Tiny primitive mammals may have emerged from their dens, to find that their giant reptile competitors were mostly gone.
Some asteroids are double bodies - an asteroid and a satellite.
Here such a pair is encountering Earth, and the distant satellite is already entering the atmosphere. Double craters have been found on Earth, caused by such pairs. An example is Clearwater Lakes in Canada. Such pairs of asteroids have also been photographed by space probes. So far there is no evidence of an asteroid impact at that time.