Sequence of Venus atmosphere images taken by the Venus Monitoring Camera (VMC) during the Venus Express orbit in July 2007. The view shows the southern hemisphere of the planet.
Credit: ESA/MPS/DLR/IDA
Thoughts on revisting Venus
As one of the brightest objects in the sky, Venus has been a major fixture in human culture for as long as records have existed. It has been made sacred to gods of many cultures, and has been a prime inspiration for writers and poets as the “morning star” and “evening star”. Venus was the first planet to have its motions plotted across the sky, as early as the second millennium BC.
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. It has the longest rotation period (243 days) of any planet in the Solar System and rotates in the opposite direction to most other planets.
It does not have any natural satellites. It is named after the Roman goddess of love and beauty.
It is the second-brightest natural object in the night sky after the Moon, reaching an apparent magnitude of −4.6 – bright enough to cast shadows at night and, rarely, visible to the naked eye in broad daylight.
Venus is a terrestrial planet and is sometimes called Earth’s “sister planet” because of their similar size, mass, proximity to the Sun, and bulk composition.
It is radically different from Earth in other respects. It has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. The atmospheric pressure at the planet’s surface is 92 times that of Earth, or roughly the pressure found 900 m (3,000 ft) underwater on Earth. Venus is by far the hottest planet in the Solar System, with a mean surface temperature of 735 K (462 °C; 863 °F), even though Mercury is closer to the Sun.
As the closest planet to Earth, Venus has been a prime target for early interplanetary exploration. It was the first planet beyond Earth visited by a spacecraft (Mariner 2 in 1962), and the first to be successfully landed on (by Venera 7 in 1970). Venus’s thick clouds render observation of its surface impossible in visible light, and the first detailed maps did not emerge until the arrival of the Magellan orbiter in 1991. Plans have been proposed for rovers or more complex missions, but they are hindered by Venus’s hostile surface conditions.
Much of the Venusian surface appears to have been shaped by volcanic activity. Venus has several times as many volcanoes as Earth, and it has 167 large volcanoes that are over 100 km (62 mi) across. The only volcanic complex of this size on Earth is the Big Island of Hawaii. This is not because Venus is more volcanically active than Earth, but because its crust is older. Earth’s oceanic crust is continually recycled by subduction at the boundaries of tectonic plates, and has an average age of about 100 million years, whereas the Venusian surface is estimated to be 300–600 million years old.
As it orbits the Sun, Venus displays phases like those of the Moon in a telescopic view. The planet appears as a small and “full” disc when it is on the opposite side of the Sun (at superior conjunction). Venus shows a larger disc and “quarter phase” at its maximum elongations from the Sun, and appears its brightest in the night sky. The planet presents a much larger thin “crescent” in telescopic views as it passes along the near side between Earth and the Sun. Venus displays its largest size and “new phase” when it is between Earth and the Sun (at inferior conjunction). Its atmosphere is visible through telescopes by the halo of sunlight refracted around it.
The Venusian orbit is slightly inclined relative to Earth’s orbit; thus, when the planet passes between Earth and the Sun, it usually does not cross the face of the Sun. Transits of Venus occur when the planet’s inferior conjunction coincides with its presence in the plane of Earth’s orbit. Transits of Venus occur in cycles of 243 years with the current pattern of transits being pairs of transits separated by eight years, at intervals of about 105.5 years or 121.5 years—a pattern first discovered in 1639 by the English astronomer Jeremiah Horrocks.
In 1967, Venera 4 found Venus’s magnetic field to be much weaker than that of Earth. This magnetic field is induced by an interaction between the ionosphere and the solar wind, rather than by an internal dynamo as in the Earth’s core. Venus’s small induced magnetosphere provides negligible protection to the atmosphere against cosmic radiation.
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images: Mattias Malmer/NASA/JPL, Peter Barvoets, Soviet Planetary Exploration Program, NSSDC, Marc Lecleire, ESA, C. Carreau,
TODAY IN HISTORY: Planet Venus, observed by NASA’s Pioneer 12 space probe on February 26, 1979.
Our Amazing Solar System!
When it landed on Venus on December 15th, 1970, Venera 7 became the first spacecraft to achieve a soft-landing on another planet. Only able to transmit surface data back to Earth for 23 minutes due to signal degradation, it was determined by Venera 7’s transmission that the atmosphere of Venus is composed 97% of carbon dioxide, with a temperature reading of 887°F (475°C).
NASA’s Innovative Advanced Concepts program is funding a study into the possible use of a sail powered rover to explore the 500°C surface temperatures of Venus.
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Please Build A Cloud City Over Venus
"NASA Langley researchers want to get a better idea about conditions on our nearest planetary neighbor, Venus, so they have come up with HAVOC or a High Altitude Venus Operational Concept – a lighter-than-air rocket ship that would help send two astronauts on a 30-day mission to explore the planet’s atmosphere. Exploration of Venus is a challenge not only because its smog-like sulfuric acid-laced atmosphere, but also its extremely hot surface temperature and extremely high air pressure on the surface."
"The video shows a human mission that’s part of a multi-phase campaign to explore and potentially settle Venus. Before the mission in the video occurred, there would be similar robotic missions to test the technologies and better understand the atmosphere. Eventually, a short duration human mission would allow us to gain experience having humans live at another world, with the hope that it would someday be possible to live in the atmosphere permanently (hinted at in the closing shot of the video)."
Moon - Venus - Mars
by Neil A.D. Taylor
Earth View from Moon by ric tan