By moving into the water full-time, the ancestors of whales paved the way for their descendants to become behemoths, largely free from gravity's constraints. Today, the blue whale is the largest animal ever to live.

Presently, astronomers only have a short period of observations to forecast the comet's path through the inner solar system and they know the probability of Mars "taking one for the celestial team" on Oct. 19, 2014, is small — in all likelihood the comet will fly by, creating a wonderful astronomical event for Earth and Mars-based observers alike.