Mariner 3 (Mariner C-2, together with Mariner 4 known as Mariner-Mars 1964) was one of two identical deep-space probes designed and built by the Jet Propulsion Laboratory (JPL) for NASA's Mariner-Mars 1964 project that were intended to conduct close-up (flyby) scientific observations of the planet Mars and transmit information on interplanetary space and the space surrounding Mars, televised images of the Martian surface and radio occultation data of spacecraft signals as affected by the Martian atmosphere back to Earth. Although the launch was initially successful, there was a separation issue and Mariner 3 stopped responding when its batteries ran out of power. It was the third of ten spacecraft within the Mariner program.

Wikipedia: https://en.wikipedia.org/wiki/Mariner_3. Related NASA reference: https://science.nasa.gov/mission/mariner-3/. Description adapted from Wikipedia contributors (CC BY-SA 4.0; https://creativecommons.org/licenses/by-sa/4.0/).