by the extended legs.

Each lander was enclosed in an aeroshell heat shield designed to slow the lander down during the entry phase. To prevent contamination of Mars by Earth organisms, each lander, upon assembly and enclosure within the aeroshell, was enclosed in a pressurized "bioshield" and then sterilized at a temperature of 111 °C for 40 hours. For thermal reasons, the cap of the bioshield was jettisoned after the Centaur upper stage powered