The computer calculates the potential impact area as a landing ellipse

Weighing all the possibilities,the computer spits out the potential area of impact in the form of a landing ellipse.In 1976, the landing ellipse for the Mars Viking Lander was 62 x 174 miles,nearly the area of New Jersey.With such a limitation,NASA had to ignore many interesting but risky landing areas.Since then, new information about the Martian atmosphere,improved spacecraft technology,and more powerful computer simulations have drastically reduced uncertainty.