According to a Greek legend, the sea god Poseidon placed the figure of <a href="/the_universe/Constellations/circumpolar/cassiopeia.html&edu=high&dev=1">Cassiopeia</a> among the stars. It is said that Cassiopeia has a ridiculous upside-down position to punish her for having been pretentious.<p><small><em>Image courtesy of 1995 Visual Language (c). All rights reserved.</em></small></p>An artist's rendering of the moment of impact of a massive <a
  href="/our_solar_system/meteors/meteors.html&edu=high&dev=1">meteorite</a>
  at the end of the Cretaceous (at the end of the <a
  href="/earth/geology/hist_mesozoic.html&edu=high&dev=1">Mesozoic
  Era</a>). Many
  scientists have concluded for decades that a meteorite four to six kilometers
  in diameter impacted the Earth at this time, resulting in a <a
  href="/earth/past/KTextinction.html&edu=high&dev=1">mass extinction
  of dinosaurs</a> and many other life forms. Recent research suggests that
 perhaps <a
  href="/headline_universe/olpa/chicxulub.html&edu=high&dev=1">massive
  volcanic eruptions</a> may be been responsible for the extinction.<p><small><em>Courtesy of Don Davis, NASA</em></small></p>The spinning vortex of <a href="https://www.windows2universe.org/saturn/saturn.html">Saturn</a>'s north polar storm resembles a giant deep red rose surrounded by green foliage in this false-color <a href="http://www.nasa.gov/mission_pages/cassini/multimedia/pia14944.html">image</a> from NASA's <a href="https://www.windows2universe.org/missions/cassini.html">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="https://www.windows2universe.org/earth/Atmosphere/hurricane/hurricane.html">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>Lunar eclipses are special events that only occur when certain conditions are met. First of all, the Moon must be in <a href="/the_universe/uts/moon3.html&edu=high&dev=1">full phase</a>. Secondly, the <a href="/sun/sun.html&edu=high&dev=1">Sun</a>, <a href="/earth/earth.html&edu=high&dev=1">Earth</a> and <a href="/earth/moons_and_rings.html&edu=high&dev=1">Moon</a> must be in a perfectly straight line. If both of these are met, then the Earth's shadow can block the Sun's light from hitting the Moon.  The reddish glow of the Moon is caused by light from the Earth's limb scattering toward the Moon, which is reflected back to us from the Moon's surface.<p><small><em>Image credit - Doug Murray, Palm Beach Gardens, Florida</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="/physical_science/chemistry/methane.html&edu=high&dev=1">methane</a>, a powerful <a href="/earth/climate/cli_greengas.html&edu=high&dev=1">greenhouse gas</a>.
Watch the NBC Learn video - <a href="/earth/changing_planet/permafrost_methane_intro.html&edu=high&dev=1">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="/earth/polar/arctic_currents.html&edu=high&dev=1">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="/earth/changing_planet/freshwater_arctic.html&edu=high&dev=1">Changing Planet: Fresh Water in the Arctic video</a>.<p><small><em> Courtesy of Jack Cook, WHOI (<a href="http://www.whoi.edu">Woods Hole Oceanographic Institute</a>)</em></small></p>

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