Venus under surveillance: an overview of space probes

Exploration of Venus

Venus, the second planet in the solar system, fascinates with its extreme conditions and initial resemblance to Earth. Since the 1960s, numerous space probes have been sent to study its dense atmosphere, chemical composition, and geology. These missions have allowed the observation of phenomena such as the extreme greenhouse effect, sulfuric acid clouds, and active volcanoes. The probes were launched by various space agencies, notably the Soviet Sergei Korolev (1907-1966) and NASA.

History of missions to Venus

The first missions to Venus were the Soviet Venera (venera) and American Mariner (mariner) programs. The Venera probes were the first to penetrate the atmosphere and transmit images from the surface. More recent missions, such as the Japanese JAXA's Akatsuki (akatsuki), have studied the climate and upper clouds.

• Venera 4 (1967): first direct measurement of the Venusian atmosphere
• Venera 7 (1970): first successful landing on Venus
• Mariner 2 (1962): first successful flyby of another planet
• Magellan (1989-1994): complete radar mapping of the surface
• Akatsuki (2010): study of climate and upper winds

Technologies and scientific instruments

Venusian probes carry various instruments: spectrometers, cloud-penetrating radars, magnetometers, and cameras. These instruments measure pressure, temperature, chemical composition, and topographical features. Radar use has been essential for mapping a surface completely invisible in the visible spectrum.

• Source: ESA – Venus Express (new window).

Possible presence of organic molecules in Venus's atmosphere

In recent years, spectroscopic studies have suggested the possible presence of organic molecules in Venus's atmosphere, particularly in the cloud layer at about 50-60 km altitude. In 2020, an international team announced the detection of PH3 (phosphine, PH3), a molecule containing phosphorus and hydrogen, via observations made with the James Clerk Maxwell Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA). Phosphine is known on Earth as a potential indicator of biological activities in anaerobic environments.

This discovery sparked great interest, as it could indicate unusual chemical processes or, more speculatively, the presence of microbial life forms in Venus's clouds. However, subsequent analyses have shown that the signals attributed to phosphine could be explained by non-biological chemical phenomena, such as photochemical reactions in the acidic atmosphere.

Future missions to Venus, such as ESA's EnVision (enVision orbiter) or the American DAVINCI+ mission, should help clarify this issue by directly measuring the chemical composition of the clouds and precisely searching for organic molecules.

• Source: Greaves et al., 2020, Nature Astronomy – Phosphine on Venus (new window).