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According to <a href="">NASA scientists</a>, the Voyager 1 spacecraft entered interstellar space in August 2012, becoming the first spacecraft to leave the <a href="/php/tour_test_sqli.php?page=/our_solar_system/solar_system.html">solar system</a>. The space probe is about 19 billion km from the <a href="/php/tour_test_sqli.php?page=/sun/sun.html">Sun</a>.  <a href="/php/tour_test_sqli.php?page=/space_missions/voyager.html">Voyager 1 and 2</a> were launched in 1977 on a <a href="/php/tour_test_sqli.php?page=/space_missions/voyager.html">mission</a> that flew them both by <a href="/php/tour_test_sqli.php?page=/jupiter/jupiter.html">Jupiter</a> and <a href="/php/tour_test_sqli.php?page=/saturn/saturn.html">Saturn</a>, with Voyager 2 continuing to <a href="/php/tour_test_sqli.php?page=/uranus/uranus.html">Uranus</a> and <a href="/php/tour_test_sqli.php?page=/neptune/neptune.html">Neptune</a>. Voyager 2 is the longest continuously operated spacecraft. It is about 15 billion km away from the <a href="/php/tour_test_sqli.php?page=/sun/sun.html">Sun</a>.<p><small><em>Image courtesy of NASA</em></small></p>The spinning vortex of <a href="">Saturn</a>'s north polar storm resembles a giant deep red rose surrounded by green foliage in this false-color <a href="">image</a> from NASA's <a href="">Cassini spacecraft</a>. The eye is 2,000 kilometers across with cloud speeds as fast as 150 meters per second.
It is not known how long this newly discovered north-polar <a href="">hurricane</a> has been active.
The view was acquired at a distance of approximately 419,000 kilometers from Saturn.<p><small><em>NASA/JPL-Caltech/SSI</em></small></p>This historic image is the first ever taken from a spacecraft in orbit about <a href="/php/tour_test_sqli.php?page=/mercury/mercury.html">Mercury</a>, the innermost planet of the solar system.  Taken on 3/29/2011 by <a href="/php/tour_test_sqli.php?page=/space_missions/robotic/messenger/messenger.html">MESSENGER</a>, it shows numerous craters across the <a href="/php/tour_test_sqli.php?page=/mercury/Interior_Surface/Surface/surface_overview.html">surface</a> of the planet.  Temperatures there can reach over 800F because Mercury is so close to the Sun and rotates so slowly.  MESSENGER entered orbit around Mercury earlier in March 2011.<p><small><em>NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington</em></small></p>There are over 900 <a href="/php/tour_test_sqli.php?page=/the_universe/uts/megalith.html">rings of stone</a> located in the British Isles. The most famous of these stone rings is of course, <a href="/php/tour_test_sqli.php?page=/the_universe/uts/stonehenge.html">Stonehenge</a>.    The stones of Stonehenge were put in place between 3,000 B.C and 2,000 B.C. by neolithic people.Some speculate that the site was built as a temple of worship of the ancient Earth deities. Some say it was used as an <a href="/php/tour_test_sqli.php?page=/the_universe/uts/stonehenge_astro.html">astronomical observatory</a> of sorts. Still others say it was a burial ground.<p><small><em>  Image courtesy of Corel Photography.</em></small></p>As permafrost thaws, the land, atmosphere, water resources, ecosystems, and human communities are affected. Coastal areas and hillsides are vulnerable to erosion by thawing of permafrost.  Thawing permafrost also causes a positive feedback to global warming, as carbon trapped within the once-frozen soils is released as <a href="/php/tour_test_sqli.php?page=/physical_science/chemistry/methane.html">methane</a>, a powerful <a href="/php/tour_test_sqli.php?page=/earth/climate/cli_greengas.html">greenhouse gas</a>.
Watch the NBC Learn video - <a href="/php/tour_test_sqli.php?page=/earth/changing_planet/permafrost_methane_intro.html">Thawing Permafrost and Methane</a> to find out more.<p><small><em>Image courtesy of the    USGS</em></small></p>Scientists are concerned that melting Arctic sea ice will increase the amount of fresh water in the <a href="/php/tour_test_sqli.php?page=/earth/polar/arctic_currents.html">Beaufort Gyre</a>, which could spill out into the Atlantic and cause major climate shifts in North America and Western Europe. Watch the <a href="/php/tour_test_sqli.php?page=/earth/changing_planet/freshwater_arctic.html">Changing Planet: Fresh Water in the Arctic video</a>.<p><small><em> Courtesy of Jack Cook, WHOI (<a href="">Woods Hole Oceanographic Institute</a>)</em></small></p>

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