For millenia, it lay benign in the night sky. Three hundred times greater than Earth; a Gentle Giant that dwarfed all the planets in our solar system. But... Jupiter concealed a deadly secret. A hostile race of beings programmed to conquer. Mysterious aliens, about whom we know nothing... except their desire to destroy our Earth. United at last, Earth's mightiest powers supply three scout ships which must scour the surface of Jupiter and relay photographs back to Earth. For this desperate journey of discovery, each ship is equipped with twin Cannons and limited Ultrasonics. More ships and weapons will be dispatched from Earth as they are ready. Until then, your mission is to gain vital information. Your strategy is to survive. Your survival will seal the destiny of mankind. For millenia, Jupiter lay benign... What happens now rests with you!