Exploration of Mars
The Viking program launched "Viking 1" and "Viking 2" spacecraft to Mars in 1975; The program consisted of two orbiters and two landers – these were the first two spacecraft to successfully land and operate on Mars.
The primary scientific objectives of the lander mission were to search for biosignatures and observe meteorologic, seismic and magnetic properties of Mars. The results of the biological experiments on board the Viking landers remain inconclusive, with a reanalysis of the Viking data published in 2012 suggesting signs of microbial life on Mars.
The Viking orbiters revealed that large floods of water carved deep valleys, eroded grooves into bedrock, and traveled thousands of kilometers. Areas of branched streams, in the southern hemisphere, suggest that rain once fell.
2016 in spaceflight
The ExoMars mission, a collaboration between the European and Russian space agencies, was launched on 14 March and reached Mars on 19 October. Dedicated to astrobiology investigations, this flight carried the ExoMars Trace Gas Orbiter, which reached Mars orbit, and the Schiaparelli EDM lander, which crashed upon landing. A subsequent flight scheduled for 2020 will carry the ExoMars rover along with four static surface instruments. 
Meanwhile, the Japanese space probe Akatsuki started its observations of Venus in May after spending five months gradually adjusting its orbit. 
Planetary exploration activities took center stage with the orbit insertion of NASA's Juno probe at Jupiter on 4 July, followed by the launch of NASA's OSIRIS-REx mission to asteroid 101955 Bennu on 8 September. Finally, on 30 September, the Rosetta probe executed a slow crash-landing on comet 67P/Churyumov–Gerasimenko.