Successfully orbits and lands on surface of Mars, transmits 20 seconds of pictures before failure. US launches Mariner 9 . Designed to orbit Mars, but engine malfunction sends craft on Mars flyby instead. Successful orbit of Mars. USSR launch of Mars 6, designed as lander.
All signals stop seconds before landing.
Engine malfunction causes potential lander craft to miss Mars. First US landing on another planet. Tremendous data return. US launches Viking 2 . A second successful landing on Mars, again much data.