Of all the ways to be humbled by another planet, tripping over your own rubbish has to be the least dignified.

On 5 March 1982 a Soviet lander called Venera 14 finished a four-month cruise, fell through a deck of sulfuric acid cloud, and touched down on a basaltic plain near the eastern flank of Phoebe Regio. Its twin had come down roughly 950 kilometres away four days earlier. Venus was waiting with a surface temperature of about 465 degrees Celsius and pressure 94 times what you’d feel at sea level on Earth. Engineers at the Lavochkin design bureau had built the machine to survive 32 minutes. It managed 57.

Busy 57 minutes, too. Cameras, a drill, spectrometers, microphones, and one small mechanical arm whose entire job was to find out how hard the ground was.

How the soil tester worked

PrOP-V, as the instrument was designated, was built to press into the Venusian ground and read how far it sank, a rough proxy for how firm the surface was. Both of the lander’s cameras looked out through thick quartz windows, each one protected during descent by a cover that popped off once Venera 14 was safely down.

One of those covers came to rest exactly where the penetrometer was due to strike.

Two very different numbers

So how solid was the ground? Venera 13 had already pressed into a surface with a fair amount of loose material underfoot. Venera 14 found almost none. Per a NASA-published report by James Garvin and colleagues at Brown University, loose soil particles were common at the Venera 9, 10 and 13 sites but scarce at Venera 14, where bare, fractured bedrock dominated instead.

Ground like that made a far higher number entirely plausible, and that is exactly what came back. The reading crossed the gap to Earth and went straight into the scientific record as real.

What the panoramas showed

Then people looked closely at the pictures. Don Mitchell, a retired Bell Labs and Microsoft researcher, reprocessed the original camera data from both landers, and it is his version of the Venera 14 panorama that NASA now runs on its own site.

Per NASA’s own caption for that image, the penetrometer sits in the lower left of the frame, and just beside it is part of the ejected lens cover. Wikipedia’s account of the mission lays out what that meant: the reading beamed back to Earth was most likely of the lens cap’s compressibility, not the ground’s.

What Venera 14 actually delivered

Quite a lot, as it turns out. The drill worked. It cut into the surface and dropped a sample into a sealed chamber, held at 30 degrees Celsius and about a twentieth of an atmosphere of pressure. From there it went to an X-ray fluorescence spectrometer. Yuri Surkov and colleagues, writing in the Journal of Geophysical Research, reported the Venera 14 site as tholeiitic basalt, chemically similar to the rock that makes up ocean floor on Earth.

That result, like the bedrock-versus-soil picture from the panoramas, is a single finding from a single pair of landers, not a settled body of literature, and nobody has been back to check. No spacecraft has landed on Venus since 1985.

So the penetrometer figure stays in the record, unretracted, carrying a permanent maybe. At its closest, Venus comes within about 38 million kilometres of Earth, and somewhere down there sits the only piece of Soviet camera hardware whose compressibility has ever been measured on location.