Mission Type: Flyby
Launch Vehicle: 8K78 (no. L1-4M)
Launch Site: NIIP-5 / launch site 1
Spacecraft Mass: 480 kg
Spacecraft Instruments: 1) ultraviolet spectrograph; 2) radiation detector and 3) cosmic-ray detector
References:
-Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, Monographs in Aerospace History No. 24, by Asif A. Siddiqi

This was the first of two Soviet Mars spacecraft intended to fly past Mars. It also was the first attempt by humans to send spacecraft to the vicinity of Mars. Although the spacecraft initially included a TV imaging system and a spectroreflectometer (to detect organic life on Mars), mass constraints forced engineers to remove both instruments a week before launch.

The mission profile called for the probe to first enter Earth orbit and then use a new fourth stage (called "Blok L") to gain enough additional velocity to fly to a Mars encounter. During the launch, violent vibrations caused a gyroscope to malfunction. As a result, the booster began to veer from its planned attitude. The guidance system failed at T+309 seconds, and the third-stage engine was shut down after the trajectory deviated to a pitch of greater than 7°. The payload eventually burned up in Earth's atmosphere over eastern Siberia without reaching Earth orbit.

The Mars flyby was planned for 13 May 1961.