Thirty years ago, on August 17, 1970, the Soviet Union launched Venera 7. It would become the first spacecraft to transmit data from another planet.

Like its predecessors, Venera 7 was launched toward Venus atop a Molniya booster. Earth's closest but mysterious planetary neighbor had become even more of an enigma as discoveries made at the time had shattered the earlier belief that the similarly sized world was an "Earth-like" planet.

The Venera 4 probe, launched in 1967 and designed to withstand around 10 atmospheres of pressure, had been obliterated at the altitude of around 16.2 miles (26 kilometers) by Venusian pressure that reached around 15 atmospheres.

Designers at the Lavochkin bureau in Moscow, who were responsible for the development of Soviet planetary spacecraft, sent reinforced follow-up probes. These probes, Veneras 5 and 6, were built to withstand up to 25 atmospheres. The modifications to these landers allowed them to descend as low as 12 miles (19 kilometers) before the atmospheric pressure destroyed them.

And not a drop of water could exist on the planet where 930-degree-Fahrenheit (500-degree-Celsius) surface temperatures were expected.

After carefully reviewing available data, Lavochkin engineers decided to design the next set of Venus probes to withstand up to 180 atmospheres.

To survive the landing, a pair of landers scheduled for launch toward Venus in 1970 were each "packed" into a titanium shells. The extra protection came with the price -- the vehicles' weight exceeded by some 44.1 pounds (20 kilograms) the capabilities of their launchers.

In a frantic search to save weight, the engineers decided to remove telemetry systems from the upper stage of the launch vehicles that would push each probe from initial Earth orbit on their way to Venus.

"This way, we barely fit into the weight requirements," said Vladimir Perminov, deputy chief designer for deep-space spacecraft at Lavochkin bureau at the time.

Each egg-shaped lander would then carry communication equipment and a multitude of sensors which would measure around two dozen factors during its descent, including external and internal temperature of the spacecraft, the pressure and the composition of atmospheric gases, etc.

Each capsule was also equipped with a parachute, which would be deployed after the craft completed the initial aerodynamic descent. The parachute was reduced in size, compared to the previous probes, in order to accelerate the landing.

In August 1970, the two probes blasted off toward Venus from Baikonur Cosmodrome: On August 17, a Molniya booster successfully inserted the first probe on its way to Venus, while its sibling, launched on August 22, was left stranded in Earth orbit.

As Venera 7 descended into the Venusian atmosphere, it continued transmitting temperature data down to the altitude of around 32 feet (10 meters). Then another disaster struck. At this point, the probe's parachute was lost and the spacecraft plummeted toward the surface of Venus.

The mission was seemingly over -- the Russian deep-space control station in Crimea was receiving nothing but background noise from the emptiness of space. Lavochkin engineers were even more stunned when a week later, the experts from the Moscow's Institute of Radio Electronics told them that they had been able to discern Venera 7's signal from the background radio noise recorded after the landing.

After deciphering a very weak signal, the scientists confirmed that for around 23 minutes after hitting the surface of another world, Venera 7, despite the fact it was laying on its side in darkness with its antennas pointed away from Earth, had continued transmitting temperature data.

The hardy spacecraft had delivered the first measurements conducted directly on the surface of another planet. The data confirmed what has already been speculated about the "weather" on Venus -- the surface temperature was 460 to 475 degrees Fahrenheit (237 to 246 degrees Celsius) -- enough to melt such metals as lead or zinc. The atmospheric pressure at the surface turned out to be around 93 atmospheres, comparable to an ocean depth on Earth of around 2,625 feet (800 meters).