Last update: October 15, 2025

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 and American 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, 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.

Space missions to Venus (landers, orbiters, and flybys)
Mission	Developed by	Launch year	Type	Scientific objective
Venera 4	USSR	1967	Lander / Atmospheric probe	Direct measurement of pressure, temperature, and atmospheric composition
Venera 5	USSR	1969	Atmospheric probe	Atmospheric and temperature measurements
Venera 6	USSR	1969	Atmospheric probe	Atmospheric and density measurements
Venera 7	USSR	1970	Lander	First successful landing and transmission of surface data
Venera 8	USSR	1972	Lander	Atmospheric analysis and surface measurements
Venera 9	USSR	1975	Lander / Orbiter	First images of the surface and geological analyses
Venera 10	USSR	1975	Lander / Orbiter	Images and atmospheric measurements
Venera 13	USSR	1981	Lander	Color images of the surface and chemical analyses of rocks
VEGA 1	USSR	1984	Orbiter / Balloon / Lander	Release of balloons in the atmosphere, study of clouds and cometary flyby
VEGA 2	USSR	1985	Orbiter / Balloon / Lander	Release of balloons in the atmosphere, study of clouds and cometary flyby
Mariner 2	NASA	1962	Flyby	First scientific measurements of temperature and solar radiation
Mariner 5	NASA	1967	Flyby	Study of the atmosphere, magnetosphere, and ionosphere
Mariner 10	NASA	1973	Flyby / Gravitational assist	Unique flyby to accelerate trajectory to Mercury, limited atmospheric measurements
Pioneer Venus 1 (Orbiter)	NASA	1978	Orbiter	Detailed study of the atmosphere and radar mapping of the surface
Pioneer Venus 2 (Multiprobe)	NASA	1978	Landers / Atmospheric probes	Measurements of temperature, pressure, atmospheric composition, and winds
Magellan	NASA	1989	Orbiter	Complete radar mapping of the surface
Venus Express	ESA	2005	Orbiter	Study of climate, clouds, ionosphere, and atmospheric structure
Akatsuki	JAXA	2010	Orbiter	Observation of upper clouds, winds, and meteorological activity
Galileo	NASA	1989	Flyby / Gravitational assist	Flyby for acceleration to Jupiter, limited atmospheric measurements
Cassini	NASA / ESA / ASI	1998	Flyby / Gravitational assist	Flyby for acceleration to Saturn, limited atmospheric measurements
MESSENGER	NASA	2004	Flyby / Gravitational assist	Flyby for acceleration to Mercury, limited measurements

Source: ESA – Venus Express.

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, 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 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.