Arriving at Uranus in 1986, Voyager 2 observed a bluish orb with extremely subtle features. A haze layer hid most of the planet’s cloud features from view. Credit: NASA/JPL-Caltech
Humanity has visited Uranus only once, 30 yrs ago. NASA’s Voyager 2 spacecraft got its closest look at the distant, gaseous planet on Jan. 24, 1986. Voyager 2 sent back stunning images of the planet and its moons during a flyby of 5.5 hrs of close study. It got within 50,600 miles of Uranus, the coldest planet in our solar system, though not the farthest from the sun, It has no internal heat source. Atmosphere of Uranus is 85% hydrogen and 15% helium. There was also evidence of a boiling ocean ~500 miles below the cloud tops.
Scientists found that Uranus has a magnetic field different from any they had ever encountered previously. At Mercury, Earth, Jupiter and Saturn, the magnetic field is aligned approximately with the rotational axis. “Then we got to Uranus and saw that the poles were closer to the equator,” Stone said. “Neptune turned out to be similar. The magnetic field was not quite centered with the center of the planet.”
Uranus’ icy moon Miranda wowed scientists during the Voyager encounter with its dramatically fractured landscapes. Credit: NASA/JPL-Caltech
This surface magnetic field of Uranus was also stronger than that of Saturn. Data from Voyager 2 helped scientists determine that the magnetic tail of Uranus twists into a helix stretching 6 million miles in the direction pointed away from the sun. Understanding how planetary magnetic fields interact with the sun is a key part of NASA’s goal to understand the very nature of space. Not only does studying the sun-planet connection provide information useful for space travel, but it helps shed light on the origins of planets and potential for harboring life.
Voyager 2 also discovered 10 new moons (there are 27 total) and 2 new rings at the planet, which also proved fascinating. An icy moon called Miranda revealed a peculiar, varied landscape and evidence of active geologic activity in the past. While only ~300 miles in diameter, this small object boasts giant canyons that could be up to 12X as deep as the Grand Canyon. Miranda also has 3 unique features called “coronae”: lightly cratered collections of ridges and valleys. This moon could have been shattered and then reassembled.
Mission planners designed Voyager 2’s Uranus encounter so that the spacecraft would receive a gravity assist to help it reach Neptune. In 1989, Voyager 2 added Neptune to its resume of first-ever looks. Voyager 2 was launched on Aug. 20, 1977, 16 days before its twin, Voyager 1. In August 2012, Voyager 1 made history as the first spacecraft to enter interstellar space, crossing the boundary encompassing our solar system’s planets, sun and solar wind. Voyager 2 is also expected to reach interstellar space within the next several years.
http://www.nasa.gov/feature/jpl/voyager-mission-celebrates-30-years-since-uranus
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