Spacecraft in deep space.

An artist's concept of NASA's Mariner spacecraft. Credit: NASA

What was Mariner 2?

NASA's Mariner 2 was the world's first successful interplanetary spacecraft. The spacecraft flew by Venus, sending back valuable new information about interplanetary space and the Venusian atmosphere.

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


  • First fully successful interplanetary mission performed by any nation

Key Dates

Aug. 27, 1962: Launch

Dec. 14, 1962: Venus flyby

Jan. 3, 1963: Last contact with spacecraft

In Depth: Mariner 2

NASA brought the Mariner R-2 spacecraft out of storage and launched it toward Venus at 06:53:14 UT Aug. 27, 1962, just 36 days after the failure of Mariner 1. Mariner 2 was equipped with an identical complement of instrumentation as its predecessor.

The mission proved to be the first fully successful interplanetary mission performed by any nation.

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.

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.

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.

NASA elected to stand down the third spacecraft in the series (Mariner R-3) scheduled for the 1964 launch period.

Key Source

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

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