Why must lander probes on Mars be sterilized before launch?
A) to prevent terrestrial microbes hitching a ride on the probe and contaminating the Martian surface
B) to prevent terrestrial microbes destroying the electronics in the probe during its passage to Mars
C) to prevent Martian dust from building up on the probe on the surface
D) to prevent Martian microbes from contaminating the lander probe
Question 2
Telescopic observations of distant galaxies have shown that the universe is
A) expanding
B) contracting
C) static and unchanging
D) infinite in size
FIRST PICTURE OF MARS
The mask covers both the mouth and nose to prevent exposure to body fluids and airborne droplets.
Lachrymal probes: (A) Bowman; (B) Williams.
Methods to prevent pregnancy
Two Hemispheres of Mars "نصفين من المريخ"
How the cortical reaction in a mouse egg is thought to prevent additional sperm from entering the eg