By Dr. Gary L. Deel, Ph.D., J.D.
Faculty Director, School of Business, American Military University
This is the second article in a seven-part series reviewing the extraterrestrial planets and other bodies of the solar system, as well as exploratory missions to study them.
Venus is one of the most interesting planets in the solar system. It has been described as Earth’s twin due to their similar size. Venus is about 82 percent of Earth’s mass. Other than the moon, Venus is the brightest object in the night sky. Unlike Earth, Venus does not have any moons. It also rotates extremely slowly, taking 243 Earth days to complete one full sidereal day. (A solar day is the time it takes for the Earth to rotate about its axis so that the Sun appears in the same position in the sky. A sidereal day is the time it takes for the Earth to complete one rotation about its axis with respect to the “fixed” stars. A sidereal day is ~4 minutes shorter than the solar day.) In fact, because Venus only takes 225 days to complete one orbit around the sun, its day is actually longer than its year.
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Venus is also the hottest planet in the solar system due to the runaway greenhouse effect created by its thick atmosphere. Temperatures exceed 900°F on the surface. A number of space agencies, including NASA, Roscosmos, the ESA, and JAXA have sent missions to study Venus.
Mariner 2 conducted the first flyby of Venus in 1962. It was supposed to be preceded by Mariner 1, but the earlier mission failed after launch. Mariner 2 was the first spacecraft to discover the intense temperatures of Venus’s surface.
In 1967, NASA launched Mariner 5. It made the closest flyby to date (at the time). Through radio occultation data Mariner 5 was able to confirm what Mariner 2 had sent back: Venus’s atmosphere is extremely dense and extremely hot.
In 1974, NASA followed with Mariner 10, which flew by Venus before heading for Mercury. Mariner 10 confirmed that Venus has a very weak magnetic field. It also photographed some of Venus’s atmosphere and observed rotating cloud formations.
The next NASA missions were Pioneer Venus 1 and 2 in 1978. The first mission was an orbiter that conducted a plethora of scientific experiments. The second was a vehicle with four separate probes that entered Venus’s atmosphere in different areas and collected data.
Finally, NASA’s Magellan orbiter was sent in 1989, and it used radar to measure surface topography. It also measured Venus’ gravitational field.
The next NASA mission, called VEXAG (Venus Exploration Group Analysis), will be a joint effort with NASA’s Russian counterparts (the Russians refer to the mission as Venera-D). The mission will consist of an orbiter and a lander that will study Venus’s atmosphere, geology, and surface chemistry. The launch is planned for 2026 or 2027.
In 1967, Roscosmos (the then-Soviet and now-Russian space agency) sent Venera 4 to Venus. Venera 4 included a probe that jettisoned and fell through Venus’s atmosphere. Venera 4 determined that the Venusian atmosphere is composed almost entirely of carbon dioxide, with trace amounts of nitrogen, oxygen, and water vapor.
The next Roscosmos missions, Venera 5 and 6, were launched in 1969 and sent more probes into the Venusian atmosphere. The probes lasted about 50 to 55 minutes each, sending back more detailed data on pressure, temperature, light, and atmospheric composition.
Venera 7 was the next Soviet mission launched in the series in 1970. It was designed to land on the surface of the planet and send data back to Earth. Venera 7 did send back limited data. However, it is assumed that its parachute failed during descent because it landed at a much higher velocity than expected. Venera 7 failed shortly after landing; scientists believe the crash landing damaged its antennas.
Venera 8 succeeded where its predecessor failed; it successfully landed on Venus in 1972. Venera 8 survived for about 50 minutes and was able to confirm that the thick cloud cover ends at high altitudes. Venera 8 also proved that light levels on the surface were suitable for photography.
Roscosmos launched Venera 9 and 10 in 1975. Venera 9 was the first to enter a Venusian orbit, and its probe was the first to photograph the surface. Venera 10 measured wind speed on the surface and took more photographs.
The next pair of Venera missions (11 and 12) were launched in 1978. These missions resulted in successful landings on Venus, though in both cases several of the scientific instruments failed after landing, including cameras.
Venera 13 and 14 were launched in 1981. These missions included probes that took photos of the ground and used instruments on their landing legs to measure ground soil compressibility.
Venera 15 and 16 were launched in 1983. They were identical orbiter spacecraft that used a special radar instrument to penetrate the Venusian cloud cover and map the planet’s topography.
The final Roscosmos missions, Vega 1 and 2, were launched in 1984. Each included a lander probe and an atmospheric balloon, which conducted a number of scientific experiments on and around Venus.
The next Russian mission, called Venera-D, will be a joint effort with NASA (the U.S. space agency refers to the mission as VEXAG). This mission, whose launch is planned for 2026 or 2027, will consist of an orbiter and a lander that will study Venus’s atmosphere, geology, and surface chemistry.
The European Space Agency (ESA) has also contributed to Venus studies. In 2005, it launched the Venus Express mission, which was put into a polar orbit to watch changes in the Venusian atmosphere over long periods of time so as to understand the dynamics thereof.
Finally, the Japanese Space Agency (JAXA) has also participated in Venus exploration and research. JAXA launched the Akatsuki mission in 2010, which consisted of an orbiter that is studying Venusian atmospheric stratification and cloud physics.
Although it’s disappointing to find that Venus is extremely inhospitable to Earth life, the numerous probes have taught us much about our own planet, including the risks of runaway global warming. Future missions should continue to reveal more of the beauty that lies beneath Venus’s cloud cover.
About the Author
Dr. Gary Deel is a Faculty Director with the School of Business at American Military University. He holds a J.D. in Law and a Ph.D. in Hospitality/Business Management. Gary teaches human resources and employment law classes for American Military University, the University of Central Florida, Colorado State University and others.