Zond 2, the Soviets’ second spacecraft to Mars, was launched November 30, 1964 just two days after Mariner 4 blasted off from Cape Canaveral. The next day, December 1, communications with Zond indicated that a serious problem had occurred. Only half of the expected level of power was available on the spacecraft, due to one of two solar panels that did not deploy properly because of a broken tug cord. Controllers freed the second panel by firing plasma engines to shake it loose but it was too late for a necessary mid-course maneuver to fine-tune its approach to Mars.
On or about February 17, 1965, the controllers made a mid-course correction, but in April the communications with Zond 2 began having more problems. On May 5, controllers were unable to raise Zond.
It is believed Zond 2 flew by Mars on August 6, 1965 and headed into interplanetary space.
In an April 1991 article in the Electronic Journal of the Astronomical Society of the Atlantic, Andrew J. LePage speculates on the true mission of Zond 2, which he describes as “probably the most mysterious of any planetary mission…by Soviet authorities.”
In the article, he cites Zond 2’s slower trajectory to Mars, arriving several weeks after Mariner 4, despite being launched only two days after the US spacecraft. Its trajectory also indicates that the probe would minimize speed once it approached Mars.
Two books from Russia, one a biography of the Soviets’ chief spacecraft designer Sergei Korolov and the other a story about an early Soviet Mars mission, strongly suggest Zond 2 could have been carrying a lander to touchdown on the Martian surface to test for signs of life.
However, the truth might never been known since Zond 2 hasn’t been heard from in almost fifty-two years.