It also obtained improved estimates of Venus' mass. Mariner 2 failed to turn up any evidence of a magnetic field, although its existence was confirmed in later visits to the planet, including the European Space Agency's Venus Express mission. Mariner 2's signal was tracked until Jan. The probe eventually entered into orbit around the sun, where it remains to this day. This graphic shows the Mariner 2 infrared temperature study of the clouds of Venus.
It was long believed that Venus, similar in size and in a close orbit to Earth, was Earth-like, and could possibly even support life. By the time of the Mariner mission, ground-based observations showed that the planet was too hot, and its CO2 atmosphere would not support life. Data from Mariner confirmed this, and also revealed that Venus has no appreciable magnetic field or radiation belts, as Earth has.
On December 14, , useful scientific information was radioed to Earth from the vicinity of another planet for the first time. The unmanned Mariner 2 spacecraft, with its six scientific instruments, passed within 34, kilometers 21, miles of Venus. Mariner 2 indicated that Venus is very hot and has no measurable magnetic fields or radiation belts. On the way to Venus, Mariner 2's instruments detected and measured the radiation, magnetic fields, and dust of interplanetary space.
Contact with Mariner 2 was lost on January 2, ; it is now in orbit around the Sun. Planetary exploration began, just as lunar exploration had, in a race between the United States and the Soviet Union to see who would be the first to place some sort of spacecraft near Venus, and Mariner 2 was the first successful spacecraft from Earth to reach the planet. Exploration of the inner solar system was not just an opportunity to best a rival in the Cold War; scientists in both the United States and the Soviet Union recognized the attraction of Venus for the furtherance of planetary studies.
Regarded as both the evening and the morning star, Venus had long enchanted humans-and all the more so since astronomers had realized that it was shrouded in a mysterious cloak of clouds permanently hiding the surface from view.
It was also the closest planet to Earth, and a near twin to this planet in terms of size, mass, and gravitation. These attributes brought myriad speculations about the nature of Venus and the possibility of life existing there in some form. For instance, in the first half of the twentieth century a popular theory held that the sun had gradually been cooling for millennia and that as it did so, the terrestrial planets of the solar system had a turn as a haven for life of various types.
Although it was now Earth's turn to harbor life, the theory suggested that Mars had once been habitable and that life on Venus was now just beginning to evolve. Beneath the clouds of the planet, the theory offered, was a warm, watery world and the possibility of aquatic and amphibious life.
Mariner 2 helped to determine that none of these speculations were true. The second in a series of planetary exploration spacecraft, this was the world's first spacecraft to fly-by a planet. Both Mariner 1 and 2 were part of a NASA planetary exploration initiative that took some of its design from the Ranger program, Mariner 2 bears a striking resemblance to the basic framework, solar panels, and antennas of its Ranger predecessor.
Although Mariner 1 was lost during launch on July 22, , Mariner 2 successfully took off on August 27, The spacecraft also experienced glitches in its magnetometer to measure magnetic fields on Venus. Most importantly, though, the spacecraft was still more than healthy enough for the Venus encounter. Controllers made final adjustments on Dec. Later that day, the spacecraft passed underneath Venus at a closest distance of about 21, miles 34, kilometers.
Mariner 2 only had a brief glimpse of the planet, but even that glance showed us a lot. It confirmed the planet was a hothouse; today we know the average temperature on the planet is degrees Fahrenheit degrees Celsius.
That was too hot for the jungles that Burroughs and others wrote about. Additionally, the spacecraft revealed the planet is under high pressure. Soviet spacecraft that later landed on Venus including Venera 13 , which beamed back color pictures were crushed within minutes of arrival.
More mysteriously, Mariner 2 showed that the planet was rotating opposite to the direction in which Earth and other planets in the solar system rotate. A Venus day is very long, by Earth standards: Earth days. Because Venus rotates so slowly, it cannot generate a magnetic field even though it has a metal core.
Mariner 2 also made fundamental discoveries of interplanetary space, showing that "the solar wind streams continuously, and the cosmic dust density is much lower than the near-Earth region," according to a NASA account of the mission. The spacecraft's last transmission to Earth was on Jan. But Mariner 2's close-up view of Venus was an important starting point for all Venusian science that has followed. Join our Space Forums to keep talking space on the latest missions, night sky and more!
And if you have a news tip, correction or comment, let us know at: community space. Elizabeth Howell is a contributing writer for Space. She is the author or co-author of several books on space exploration. Elizabeth holds a Ph. She also holds a bachelor of journalism degree from Carleton University in Canada, where she began her space-writing career in Besides writing, Elizabeth teaches communications at the university and community college level, and for government training schools.
To see her latest projects, follow Elizabeth on Twitter at howellspace.
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