Venera 7 — first landing on another planet
On 15 December 1970 the Soviet probe Venera 7 reached the surface of Venus. The faint signal it sent while lying on its side was the first radio message ever received from the ground of another planet.
Available views: Orbit ✓ · Sky — (not visible in the sky)
The story
On 15 December 1970 the Soviet probe Venera 7 descended through the thick atmosphere of Venus and reached the surface. It had left Earth on 17 August and travelled for four months. The part that went down to Venus was a round landing capsule weighing about 500 kg. The signal it sent from the ground became the first radio message ever received on Earth from the surface of another planet.
The descent did not go to plan. The parachute began to fail on the way down, and in the end the capsule hit the ground at about 16.5 metres per second, much faster than intended. That is roughly the speed of an object falling from the top of a three-storey building. Scientists think the impact made the capsule bounce and tip onto its side, so its antenna no longer pointed properly at Earth.
Because of this, the signal was nearly missed. After landing the probe seemed to fall silent, and controllers assumed it had failed. A few weeks later, however, the radio astronomer Oleg Rzhiga went back over the recorded tapes and found about 23 minutes of very weak signals. They had come from the toppled capsule through its misaligned antenna.
That faint signal carried the surface temperature: about 475 °C, far hotter than the 327 °C at which lead melts. From this temperature and models of the atmosphere, scientists calculated the pressure at the surface as about 90 times that on Earth. That is similar to the pressure about 900 metres under the sea. The orbit view reproduces the probe's four-month journey from Earth toward the orbit of Venus.
Mission goals
Venera 7 was the first to show that a probe could get all the way down to another planet's surface and send a signal from there. Entering the atmosphere, slowing down by parachute, surviving the impact and transmitting from a scorching surface are steps every lander has to pass. Venera 7 was the first to get through all of them. It did so lying on its side, but those 23 minutes opened the way for the landers that followed.
The landing also gave the first direct measurement of how hot the surface of Venus is. Radio observations and the American Mariner 2 flyby in 1962 had already suggested that Venus was very hot. The reason is its thick carbon-dioxide atmosphere, which traps heat; this is called the greenhouse effect. Because of this, Venus is often used as an example of what happens when the greenhouse effect runs out of control.
Mission chronology and background
The Soviet Union had sent probes to Venus before Venera 7. Venera 4 (1967) was crushed by the pressure on its way down, and Veneras 5 and 6 (1969) also passed their pressure limits before reaching the ground. The air of Venus turned out to be far heavier than expected. So Venera 7 was built much stronger, to withstand about 180 atmospheres, and it finally reached the surface.
The Venera series then went further. In 1975 Venera 9 sent back the first photograph from the surface of Venus, and in 1982 Venera 13 returned colour pictures and an analysis of the soil. Venera 13 lasted 127 minutes on the scorching ground, still the longest any lander has survived on Venus. Shields against heat and pressure can only buy a little time.
Venus is becoming a target again. NASA's DAVINCI, a probe that will descend through the atmosphere, and VERITAS, a radar mapper, together with ESA's EnVision, are being prepared for launch in the early 2030s. No new Venus lander is planned yet, however. So everything we know directly from the surface of Venus still comes from the Soviet Venera and Vega landers of half a century ago.
Where to see it — sky and simulator
Venera 7's capsule should still lie near 5° S, 351° E on Venus. But Venus is always covered by thick cloud, so no telescope can see its surface. The shape of the ground became known in detail only in the 1990s, when the American Magellan spacecraft mapped the planet with radar that sees through cloud. On that map the landing region appears as a wide plain.
Venus itself is easy to see. Select it in the sky view to find out whether it is in the morning or evening sky from where you are, and what its phase is. After the Sun and the Moon it is the brightest object in the sky, so it stands out clearly to the naked eye. Move the orbit view to 15 December 1970 and it reproduces the positions of Earth and Venus on landing day.
See this for yourself — replay the moment in the orbit view
FAQ
How long did it transmit from the surface?
About 23 minutes. The signal from the toppled capsule was so weak that it was found only weeks later, when the recorded tapes were re-examined.
How hot is the surface of Venus?
Venera 7 measured about 475 °C, far hotter than the melting point of lead, with a pressure about 90 times that on Earth.
Why do Venus landers not last long?
Because of the intense heat and pressure. Insulation and a strong shell only buy time, and Venera 13's 127 minutes is still the record.
When is the next Venus landing?
No lander is planned yet. NASA's DAVINCI aims to descend through the atmosphere of Venus in the early 2030s.
Related
- Mariner 2 — first planetary probe
- The 2012 transit of Venus
- BepiColombo — to Mercury
- Venus — object index
- Earth — object index
Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.