Venera 4
First probe to analyze another planet's atmosphere in situ.
Venera 4, also known as 4V-1 No.310, was a Soviet spacecraft sent to Venus. It had two parts: a lander meant to descend through the planet’s atmosphere by parachute, and a carrier spacecraft that transported the lander and relayed its signals. In 1967, it became the first probe to successfully analyze another planet’s environment on location. It gave the first chemical breakdown of Venus’s atmosphere, finding it mostly carbon dioxide, with a few percent nitrogen and less than one percent oxygen and water vapor. It was also the first spacecraft to survive entering another planet’s atmosphere. The probe detected a weak magnetic field and no radiation field. The outer atmosphere had very little hydrogen and no atomic oxygen. Its direct measurements confirmed that Venus is extremely hot, its atmosphere is much denser than expected, and it lost most of its water long ago.
The carrier spacecraft was 3.5 meters tall, with solar panels spanning 4 meters and covering 2.5 square meters. It carried a 2-meter magnetometer, an ion detector, a cosmic ray detector, and an ultraviolet spectrometer for detecting hydrogen and oxygen. These instruments were meant to work until the craft entered Venus’s atmosphere, at which point it would release the lander and break apart. The rear of the carrier had a liquid-fuel thruster for course corrections. The mission planned two major course adjustments, and the station could receive and execute up to 127 commands from Earth. The front held a nearly spherical landing capsule, 1 meter in diameter and weighing 383 kilograms. Compared to earlier failed Venera probes, this capsule had a better heat shield, able to withstand temperatures up to 11,000 °C. It used a simpler, more reliable gas cooling system instead of the previous liquid design. Its durability was tested in three special setups: a high-temperature vacuum system mimicking the upper atmosphere, pressurization up to 25 atmospheres (since Venus’s surface pressure was unknown, estimated from a few to hundreds of atmospheres), and a centrifuge subjecting it to 450 g. The centrifuge cracked some electronics and cable brackets, which were replaced just before launch. The launch window was tight to take advantage of the least energy-demanding path to Venus. The capsule could float if it landed in water, so its lock was made of sugar, designed to dissolve and release transmitter anten
- field
- Space exploration
- nationality
- Soviet
- known_for
- First successful in-place analysis of another planet's atmosphere; first spacecraft to survive entry into another planet's atmosphere
Lore & Background
Venera 4 was launched on 12 June 1967 by a Molniya-M carrier rocket from the Baikonur Cosmodrome. A course correction was performed on 29 July when it was 12,000,000 kilometres from Earth; otherwise, the probe would have missed Venus. On 18 October 1967, the spacecraft entered the Venusian atmosphere with an estimated landing place near 19°N 38°E. The descent lasted 93 minutes, with the capsule deploying its parachute at about 52 kilometres altitude and transmitting data until signal termination at 26 kilometres, where temperature reached 262 °C and pressure 22 standard atmospheres.
Reader's Guide
Venera 4 provided the first chemical analysis of the Venusian atmosphere, showing it to be primarily carbon dioxide with a few percents of nitrogen and below one percent of oxygen and water vapor. It detected a weak magnetic field and no radiation field, and its data proved Venus was extremely hot, its atmosphere far denser than expected, and that it had lost most of its water long ago. The mission was considered a complete success, especially given several previous failures of Venera probes. The data was analyzed together with Mariner 5 data under a combined Soviet–American working group of COSPAR in 1969, allowing a more complete profile of the Venus atmosphere. The measured ratio of carbon dioxide to nitrogen corrected previous estimates so much that some scientists contested the observations.
Did You Know?
- The capsule's heat shield could withstand temperatures up to 11,000 °C.
- The capsule's lock was made of sugar, meant to dissolve in liquid water to release transmitter antennas.
- The radar altimeter had an integer ambiguity of 30 kilometres, leading to initial misinterpretation of the descent altitude.
- The capsule was pressurized up to 25 atmospheres before launch to test durability.
Frequently Asked Questions
What is Venera 4?
Venera 4 (Soviet designation 4V-1 No. 310) was a two-part probe sent to Venus in 1967. It comprised a carrier spacecraft and a parachute-equipped lander designed to descend through the planet's atmosphere.
What did Venera 4 discover about Venus's atmosphere?
Its lander delivered the first on-site chemical reading of Venus's air, showing it was overwhelmingly carbon dioxide with a few percent nitrogen and under one percent each of oxygen and water vapor.
What was Venera 4's landmark 'first'?
It was the first spacecraft to survive re-entry into another planet's atmosphere and the first to perform in-situ analysis of a foreign planet's environment.
How did Venera 4 carry out its mission?
The carrier spacecraft ferried the lander to Venus, then released it to fall by parachute while continuing to relay the lander's atmospheric readings back to Earth.
Why is Venera 4 important to space exploration history?
It proved that a machine could endure the crushing, corrosive conditions of another world's atmosphere and still transmit real scientific data, paving the way for every planetary lander that followed.
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