Completed 60 years ago

Humanity's first close-up look at another planet was full of surprises. Mariner 2 found Venus to be far hotter and inhospitable than the imagined tropical world hidden by thick clouds.

Mission Type
Venus Flyby
4 Months
Aug. 27, 1962
06:53:14 UT
Dec. 14, 1962
42 Minutes
Two men displaying a 25-foot printout of all the data from the first planetary flyby in history.
Displaying Mariner 2 flyby data at JPL. Credit: NASA/JPL-Caltech


Launched 36 days after the loss of Mariner 1, Mariner 2 carried the same scientific equipment as its predecessor. After a course correction on Sept. 4, 1962, the spacecraft flew by Venus at a range of 21,660 miles (34,854 kilometers) at 19:59:28 UT Dec. 14, 1962.

During a 42 minute scan of the planet, Mariner 2 gathered significant data on the Venusian atmosphere and the surface before continuing on to heliocentric orbit. The radiometers, in particular, were able to conduct five scans of the night side of the planet, eight across the terminator, and five on the daylight side.

Illustrated diagram of the Atlas-Agena rocket and Mariner spaecraft combination.
A diagram of the Mariner series of spacecraft and launch vehicle. Mariner spacecraft explored Mercury, Venus and Mars. Credit: NASA/JPL-Caltech

NASA maintained contact until 07:00 UT Jan. 3, 1963, when the spacecraft was 53.9 million miles (86.7 million kilometers) from Earth, a new distance record for a deep space probe.

Goals & Accomplishments

The data returned implied that there was no significant difference in temperature across Venus. Readings from Mariner 2’s microwave radiometer indicated temperatures of 421 degrees Fahrenheit (216 degrees Celsius) on the dark side to 459 degrees Fahrenheit (237 degrees Celsius) on the dayside.

Mariner 2 also found that there was a dense cloud layer that extended from 35 to 50 miles (56 to 80 kilometers) above the surface. The spacecraft detected no discernable planetary magnetic field, partly explained by the great distance between the spacecraft and the planet.

In terms of scientific results, Mariner 2 was only a modest success, but it still retains the honor of being the very first successful planetary science mission in history.

“There will be other missions to Venus, but there will never be another first mission to Venus, ”JPL Project Manger Jack James said of Mariner 2.


Nation United States of America (USA)
Objective(s) Venus Flyby
Spacecraft P-38 / Mariner R-2
Spacecraft Mass 449 pounds (203.6 kilograms)
Mission Design and Management NASA / JPL
Launch Vehicle Atlas Agena B (Atlas Agena B no. 6 / Atlas D no. 179 / Agena B no. 6902)
Launch Date and Time Aug. 27, 1962 / 06:53:14 UT
Launch Site Cape Canaveral, Fla. / Launch Complex 12
Scientific Instruments 1. Microwave Radiometer
2. Infrared Radiometer
3. Fluxgate Magnetometer
4. Cosmic Dust Detector
5. Solar Plasma Spectrometer
6. Energetic Particle Detectors
7. Ionization Chamber

Mariner 2's hexagonal base was 3.4 feet (1.04 meters) across and 1.2 feet (0.36 meters thick). Magnesium housings contained the electronics, attitude control gas bottles, and rocket engine. Science experiments attached to a tall pyramid-shaped mast. The total height of the spacecraft was 12 feet (3.66 meters). A large directional antenna dish attached to the the base.

Mariner 2 got power from two solar cell wings. One right was 72 inches x 30 inches (183 x 76 cm). The other panel was 60 x 30 inches (152 x 76 cm) with a (31 cm) solar sail to balance solar pressure on the panels. The panels powered the spacecraft in sunlight. A a 1,000 watt-hour rechargeable batter stored power for later use.

Communications consisted of a three watt transmitter. A large and small antenna sent science data back to Earth.

Mariner 2 used a monopropellant (anhydrous hydrazine) 225 N retro-rocket for maneuvers. Nitrogen gas jets kept the spacecraft stabilized.


Mr. James S. Martin, Jr. Project Manager NASA / JPL
Dr. R. C. Wyckoff Project Scientist NASA/ JPL

Key Sources

Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.

National Space Science Data Center Master Catalog. Mariner 2, Accessed 2 November 2022.

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