For this week in rocket history, we highlight a groundbreaking milestone in Venus exploration: Venera 9.

Venera 9 was launched on June 8, 1975, on a Proton K/Blok D heavy-lift rocket from the Baikonur Cosmodrome, Site 81. The spacecraft was much bigger than the previous Venera spacecraft, nearly five metric tons, and just like those earlier versions, it was a variant of a spacecraft originally designed for a Mars mission.

Now, in the early days of uncrewed planetary missions, both the Russians and Americans launched pairs of probes during a planetary alignment. This way, if one of the probes failed they would still have a chance at results with the other one. So both Venera 9 and Venera 10 launched in summer 1975.

Both missions combined an orbiter and a lander. The orbiters were designed to image the planet in different wavelengths and perform other observations after dropping off the landers, which were intended to reach the surface of Venus. On October 20, 1975, Venera 9’s 1.5-metric ton entry capsule separated from the orbiter. The orbiter then made a burn to avoid following the lander down to the surface of the planet and set up an orbital insertion.

The capsule’s entry speed into the atmosphere was just under 11 km/s. At an altitude of 65 kilometers, a drogue parachute and a pilot parachute deployed to pull away the top of the heatshield. Shortly afterward, the main chute was deployed, reducing the velocity to 150 m/s. The final set of parachutes, four massive “canopy” parachutes with a total area of 180 square meters, deployed, and the bottom of the heatshield was jettisoned. All of these parachutes allowed the lander to fall slowly enough to study the atmosphere on the way down.

After twenty minutes on the canopy chutes, the lander was released to freefall. Venus’s lower atmosphere is extremely dense, so the lander could survive an impact at terminal velocity. The bottom of the lander was designed as a crumple zone to cushion the lander on its surface impact. The Venera 9 lander touched down at 05:13 UTC on October 22. The touchdown was in Beta Regio. In planetary geology, Regio means “a large area marked by reflectivity or color distinctions from adjacent areas.”

The lander transmitted for 53 minutes after touchdown, taking the first pictures of the surface. These pictures showed a surface covered in flat rocks. The Venera 10 lander transmitted for 65 minutes, and its pictures showed a smoother surface than the Venera 9 landing site 2,200 kilometers away. Both landers were only intended to last 30 minutes. They also each attempted a 360-degree panorama of their landing site with two cameras, but the lens cap on one of the cameras failed to eject, so the landers only managed images from one camera each.

Both landers discovered that the rocks on the Venusian surface were closer to basalt than granite, contradicting a previous theory. For basalt-like rocks to form, lava must have erupted to the surface and cooled quickly. For granite-like rocks to form, magma would have cooled slowly under the surface and only been revealed after lots of erosion. What this means is that Venus had surface volcanism at some point in the past.

Even though the Venera 9 and 10 landers only survived about an hour after touchdown, the mission continued high above the clouds, with their orbiters continuing to transmit data until mid-1976.

More Information

Beyond Earth: A Chronicle of Deep Space Exploration (NASA)

Descriptor Terms (USGS)

Venera 9 and 10 to Venus (Drew Ex Machina)