New observations by the MESSENGER spacecraft provide  support for the hypothesis that Mercury harbors abundant water ice and other frozen volatile materials in its permanently shadowed (shown in red) polar craters. Areas where polar deposits of ice imaged by Earth-based radar are shown in yellow.<p><small><em>Image courtesy of NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/National Astronomy and Ionosphere Center, Arecibo Observatory</em></small></p>On May 20, 2013, a massive EF5 <a href="">tornado</a> hit Moore, Oklahoma, devastating communities and lives.  The tornado, on the ground for 40 minutes, took a path through a subdivision of homes, destroying block after block of homes, and hitting two elementary schools just as school was ending as well as a hospital. Hundreds of people were injured, and 24 were killed.<p><small><em>Image courtesy of Ks0stm, Creative Commons Attribution-Share Alike 3.0 Unported license</em></small></p>This first global map of <a href="">ocean</a> surface saltiness, released in September 2012 by the NASA Aquarius mission team, shows the distribution of salt in the first 2 cm of the Earth's ocean. <a href="">Salinity</a> variations are one of the main drivers of <a href="">ocean circulation</a>, and are closely connected with the <a href="">cycling of freshwater</a> around the planet. High salinity is seen in the Mediterranean, Atlantic, and the Arabian Sea.<p><small><em>Image courtesy of NASA/GSFC/JPL-Caltech</em></small></p>An artist's rendering of the moment of impact of a massive <a
  at the end of the Cretaceous (at the end of the <a
  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&dev=">mass extinction
  of dinosaurs</a> and many other life forms. Recent research suggests that
 perhaps <a
  volcanic eruptions</a> may be been responsible for the extinction.<p><small><em>Courtesy of Don Davis, NASA</em></small></p>Scientists at the University of Michigan have found that <a href="/earth/polar/cryosphere_permafrost1.html&dev=">permafrost</a> in the <a href="/earth/polar/polar_north.html&dev=">Arctic</a> is extremely sensitive to sunlight.  Exposure to sunlight releases carbon gases trapped in the permafrost, including <a href="/earth/climate/earth_greenhouse.html&dev=">climate-warming</a> <a href="/physical_science/chemistry/carbon_dioxide.html&dev=">carbon dioxide</a>, to the <a href="/earth/Atmosphere/overview.html&dev=">atmosphere</a> much faster than previously thought.<p><small><em>George Kling, The University of Michigan</em></small></p>How did life evolve on <a href="/earth/earth.html&dev=">Earth</a> during the <a href="/earth/past/Archean.html&dev=">Archean</a>, when the <a href="/sun/sun.html&dev=">Sun</a> was about 25% weaker than today?  The Earth should have been <a href="/earth/polar/cryosphere_glacier1.html&dev=">glaciated</a>, if <a href="/earth/climate/earth_greenhouse.html&dev=">greenhouse</a> gas concentration was the same as today.  <a href="">Researchers</a> studying the <a href="/physical_science/physics/atom_particle/isotope.html&dev=">isotopic</a> signatures of Earth's early atmosphere in <a href="/earth/geology/rocks_intro.html&dev=">rocks</a> from Northern Australia have ruled out high levels of <a href="/physical_science/chemistry/nitrogen_molecular.html&dev=">nitrogen</a> as a possible way to increase warming from <a href="/earth/Atmosphere/overview.html&dev=">atmospheric</a> <a href="/physical_science/chemistry/carbon_dioxide.html&dev=">carbon dioxide</a>.<p><small><em>Image courtesy of Manchester University</em></small></p>

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