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Hands On Mineral Identification helps you to identify over 14,500 minerals! By M. Darby Dyar, Ph.D. See our DVD collection.
<p>The United Nations <a href="" target="_blank">estimated</a> that between 1994-2015, there were 6,873 natural disasters worldwide, which affected 218 million people and claimed 1.35 million lives. </p>
<p>Check out the materials about natural disasters in <a href="/earth/natural_hazards/when_nature_strikes.html&edu=high">NBC Learn Videos</a>, and their earth system science connections built up by the related secondary classroom activities.</p><p><small><em>NBC Learn</em></small></p>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="/our_solar_system/solar_system.html&edu=high">solar system</a>. The space probe is about 19 billion km from the <a href="/sun/sun.html&edu=high">Sun</a>.  <a href="/space_missions/voyager.html&edu=high">Voyager 1 and 2</a> were launched in 1977 on a <a href="/space_missions/voyager.html&edu=high">mission</a> that flew them both by <a href="/jupiter/jupiter.html&edu=high">Jupiter</a> and <a href="/saturn/saturn.html&edu=high">Saturn</a>, with Voyager 2 continuing to <a href="/uranus/uranus.html&edu=high">Uranus</a> and <a href="/neptune/neptune.html&edu=high">Neptune</a>. Voyager 2 is the longest continuously operated spacecraft. It is about 15 billion km away from the <a href="/sun/sun.html&edu=high">Sun</a>.<p><small><em>Image courtesy of NASA</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>Scientists at the University of Michigan have found that <a href="/earth/polar/cryosphere_permafrost1.html&edu=high">permafrost</a> in the <a href="/earth/polar/polar_north.html&edu=high">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&edu=high">climate-warming</a> <a href="/physical_science/chemistry/carbon_dioxide.html&edu=high">carbon dioxide</a>, to the <a href="/earth/Atmosphere/overview.html&edu=high">atmosphere</a> much faster than previously thought.<p><small><em>George Kling, The University of Michigan</em></small></p>As temperatures rise and soil moisture decreases, plants are stressed, which can lead to <a href="/earth/climate/crops_withering.html&edu=high">crop withering</a>. <a href="/teacher_resources/online_courses/health/events_health.html&edu=high">Droughts</a> accompanied by increased temperatures can lead to famine, social and political disruptions. Scientists are  helping with early identification of drought that might trigger food shortages. Watch the NBC Learn video - <a href="/earth/changing_planet/withering_crops_intro.html&edu=high">Changing Planet: Withering Crops</a> to find out more.<p><small><em>Image taken by Tomas Castelazo, Creative Commons <a href=&quot;;>Attribution 3.0 Unported</a> license.</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">full phase</a>. Secondly, the <a href="/sun/sun.html&edu=high">Sun</a>, <a href="/earth/earth.html&edu=high">Earth</a> and <a href="/earth/moons_and_rings.html&edu=high">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>

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA