Here is what Soviets saw when they landed a spacecraft on an alien planet

There is no place like earth here, yet billions of years ago, there may have been. 

There is no place like earth here, yet billions of years ago, there may have been.  On March 27, 1972, Venera-8, a Soviet atmospheric space probe and lander, surveyed the surface of our planetary neighbor, Venus. It was the planet's second spacecraft to successfully land.

Surprisingly, despite our inability to see the planet's surface from orbit, Venera-8 produced some eye-opening findings concerning the visibility of Venus' surface and supplied critical geochemical data that support the planet's designation as Earth's sister.

Many people consider Mars to be Earth's younger sister, despite the fact that Mars is 34 million miles away. However, at the closest point in its orbit to Earth, Venus is 25 million miles closer to our planet. Earth and Venus are likewise close in size and mass, but the Red Planet is around half the size of Earth.

Earth and Venus seem to have been twin sisters early in their histories (minus a Venusian moon). According to a 2016 article published by NASA scientist Michael Way and his colleagues, Venus may have had water until 700 million years ago. If such is the case, could Venus's present condition be indicative of Earth's future?

Space exploration trends have shifted away from Venus's hot and dense atmosphere and toward Mars's cooler and thinner atmosphere. Since 1985, when the Soviet Union launched Vega 2, no lander has been deployed to Venus' surface. We seem to have overlooked that “Venus is Earth’s sister across the board; not twin sister, but they’re sisters,” Gregory Shellnutt, renowned professor of geochemistry at National Taiwan Normal University, says.

Between 1961 and 1983, the Soviet Union advanced in the space race with the Venera program, deploying 28 spacecraft. Venera-8 was not only the second man-made object to land on Venus but also the first to do so successfully. Venera-7, which launched two years previously, was the first spacecraft to make a partly successful landing on another planet. However, a parachute malfunction led the lander to tumble into free fall, severely damaging it and depriving it from sending continuous, high-quality data.

Thirteen spacecraft successfully entered Venus' atmosphere during the Soviet Union's 18-year Venera mission; eight landed on the planet.

Venera-8 was launched on March 27, 1972, with the mission of studying Venus's atmosphere and surface. It took 118 days for the spacecraft to reach the planet. Venera-8's fall through the atmosphere to the surface was constructed with a cooling system to extend the life of the equipment. This is because the surface temperatures of Venus may reach temperatures over the melting point of lead during the day (620 degrees Fahrenheit).

Venera-8 was equipped with a gamma-ray spectrometer, gas analysis equipment, an altimeter, a photometer for measuring light, pressure, and temperature sensors, and a radio transmitter. Venera-8's mission was to confirm the measurements of Venus' atmosphere made by Venera-7, which despite landing issues, managed to record the atmosphere's composition as 97 percent carbon dioxide. Additionally, it measured the surface temperature at 887 degrees Fahrenheit and the pressure at 9.0 MPa (vs. 0.1 MPa on Earth). These observations quickly established that Venus's surface is devoid of water and is not a suitable habitat for humans.

Venus, too, lacks a magnetic field, or if it has, it is very feeble. This is because the surface of Venus is reaching the Curie temperature, as Shellnutt explains. The Curie temperature is the temperature at which a substance loses its magnetic characteristics.

Venera-8 confirmed Venera-7's readings, however, due to Venera-8's very good landing, Venera-8's photometer reported something unexpected.

Despite the fact that visibility through the murky Venusian atmosphere to the planet's surface was difficult, visibility on the planet's surface was comparable to that on Earth on a foggy day, with visibility of around one kilometer in each direction. Clouds were seen at a great height in the sky. Following the landing of Venera-8, engineers working on the Venera project discovered that it would be able to picture the surface. Thus, in 1975, Venera-9 not only landed successfully but also became the first lander to photograph the surface of a planet other than Earth.

Thus, in 1975, Venera-9 not only landed successfully but also became the first lander to photograph the surface of a planet other than Earth.

Venera-8 lasted less than one hour on Venus's scorching surface.

Venera-8 also measured the amounts of three radioactive elements in Venus' surface material during the 50 minutes and 11 seconds following landing: thorium, potassium, and uranium. These are trace elements on Earth, meaning they are present in trace amounts and in basalts, such as those found in Hawaii or at mid-ocean ridges.

Shellnutt, who has been captivated with Venus since he was ten years old, has tracked the evolution of Venus study throughout his career. He recalls using crystallization modeling software to analyse rocks on Earth when he came across the Venera-8 gamma-ray spectrometer trace element data — and was immediately reminded of all of the Venus missions and their geochemical data.

Venera-8 was unusual in that its data exhibited a significant abnormality in comparison to those of many previous landers. Shellnutt argues that even with 30% error margins, Venera-8 discovered trace element levels that were too high to qualify as basalts found along a mid-ocean ridge or in Hawaii. Unlike Venera-8, the other Venus landers detected geochemical values more like those seen in or around a mid-ocean ridge.

“Most of the radiation we receive naturally is from potassium in crystal rocks. It’s true for the Moon. It's true for Mars. It’s true for any terrestrial planet,” says Shellnutt.

Shellnutt describes in a 2019 paper titled "The curious case of the Venera-8 rock" how he calculated that the trace element values at the Venera-8 landing site may be comparable to a type of continental crust on Earth called Archean greenstone belts by applying his Earth-based crystallization modeling techniques to them. Archean is a term that refers to a time period on Earth between 2.5 and 4 billion years ago. Greenstone belts are a form of continental crust that many scientists believe chemically emerged from mafic basalts over billions of years.

During the Archean, the Earth appeared much different. The planet had just recently been created and was scorching hot. Earth's tectonic regime throughout this time period, as well as Venus's present and historical tectonic regimes, remain a mystery due to their heat. There is currently no evidence of plate tectonics on Venus in the sense that we understand them on Earth.

Venus' geography is also considerably distinct from that of Earth. Shellnutt depicts the magnificent volcanic edifices and landmasses the size of Africa — but with one important distinction.

“If we look at the Archaean Earth, there’s tremendous debate of whether modern plate tectonics operated during the Archaean. So how do you get these landforms [on Venus]? How does all this deformation occur? There’s evidence of compression mountains on Venus. There’s evidence of rifts, so it’s obviously tectonically active, but it’s just not broken into plates,” he says.

Reference(s): Space.com