Misconceptions:
Incorrect:
The ozone hole is there all the time.
Correct:
The ozone hole is in Antarctica and opens each year during the
Antarctic springtime.
Incorrect:
Antartica is the continent around the South Pole.
Correct:
Note the spelling: the Arctic is in the north, and the second of those
"c"'s remains in "Antarctica."
spaceflight.nasa.gov has information about the International Space Station and other NASA projects.
For information on how to see the ISS in the
night sky, visit:
http://spaceflight.nasa.gov/realdata/tracking/
http://spaceflight.nasa.gov/realdata/sightings/index.html
You can view satellite photos for most places in the U.S. and many places elsewhere. For urban areas, you can even specify a street address.
http://www.globexplorer.com/gexservlets/gexhtml
Home page: http://www.globexplorer.com/
Microsoft has a similar site ( http://terraserver.microsoft.com), but Globexplorer.com is easier to use.
Space physicists have made the first direct observations of the process that causes auroras and magnetic disturbances -- or space weather -- around the Earth. Settling a fifty-year-old debate, scientists have directly measured the transfer of energy from the solar wind into the magnetic space around Earth, or magnetosphere, and down to the atmosphere. Such events can affect radio communications, spacecraft operations, and the control of electric power systems on Earth.
Relying on observations collected by NASA's Polar spacecraft and Japan's Geotail spacecraft, scientists associated with the International Solar-Terrestrial Physics (ISTP) program have gathered the first direct evidence that a process known as magnetic reconnection occurs naturally in the Sun-Earth system. Until now, reconnection had only been observed under contrived conditions in a few physics laboratories.
During reconnection, magnetic fields that are heading in opposite directions -having opposite north or south polarities -- break and connect to each other. In space, reconnection between the magnetic fields of the Earth and Sun allows the solar wind to break through the planet's magnetic shell and flow into the space around Earth. Along the way, magnetic energy gets converted to bursts of particle energy that create auroras - "northern or southern lights" -- and space weather storms.
Indirect evidence of reconnection has provoked debate for more than half a century, as space physicists could only detect signs of reconnection after it had happened. But recently, the Polar spacecraft flew through a region on the sunlit side of Earth where reconnection was in progress, gathering the first eyewitness account of the process. Using data collected from Geotail's dozens of passes through Earth's magnetic tail, scientists also have pinpointed the area on the night side where reconnection occurs, and have shown for the first time a clear association between reconnection and auroras.
"Reconnection is the fundamental process for transferring and exchanging energy in the Sun-Earth system," said Dr. Atsuhiro Nishida, a researcher with the Japan Society for the Promotion of Science and the recently retired Director-General of Japan's Institute of Space and Astronautical Science (ISAS). "Reconnection on the day side of Earth is critical for allowing solar wind energy to come into the magnetosphere. Night-side reconnection is critical for the transfer of that energy down to the atmosphere."
Nishida and colleagues presented their results today at the spring meeting of the American Geophysical Union, held in Washington, D.C.
While crucial for understanding space weather, the direct observation of reconnection around Earth has implications for many fields of physics. Reconnection on the Sun likely plays a role in the development of solar flares and of coronal mass ejections. Similar magnetic activity outside our solar system may explain some of the galactic X-rays that astronomers have detected. And observations of reconnection in nature may aid the study of nuclear fusion and other plasma processes in the laboratory. The magnetosphere is the only place where reconnection has been observed first-hand as it occurs naturally.
A popular misconception holds that auroras and space weather are caused when electrically charged particles from the Sun plunge directly into Earth's atmosphere near the magnetic poles. But in fact, the Sun provides the energy -- but not necessarily the particles -- to drive space weather activity around Earth. And rather than a direct trip from the solar atmosphere to Earth's poles, solar wind and storms from the Sun must pass through these small and elusive reconnection regions before they can stir up space weather.
"The magnetosphere acts like a great magnetic cocoon around the Earth," said Dr. Jack Scudder, professor of physics at the University of Iowa and principal investigator for the Hot Plasma Analyzer (HYDRA) on NASA's Polar spacecraft. "There are often times when the solar wind creates tears in this cocoon, allowing charged particles and energy from the Sun to enter the space around Earth. This tearing - reconnection - is what we directly observed with Polar."
Once these "tears" open up - scientists call them "reconnection regions" - the magnetic field of the solar wind becomes directly linked to the magnetosphere. Solar energy floods into the system, overloading and destabilizing it. The energy excites the particles already trapped around the Earth and stretches the magnetic tail like taut rubber bands, forcing reconnection to happen again -- this time inside Earth's space. As magnetic field lines on the night side snap and reconnect, they shoot energy stored in the tail down toward the auroral zones near the poles and into the radiation belts.
When the solar wind and magnetospheric fields reconnect, it opens a valve or faucet that lets the solar wind energy cross the magnetopause and pour into the magnetosphere," said Dr. Jeffrey Hughes, chairman of the department of astronomy at Boston University. "Without reconnection, the magnetosphere would be a very benign place."
Over the past eight years, ISAS's Geotail spacecraft has systematically studied and surveyed the magnetic tail of Earth in search of this process. As a result, scientists have been able to pinpoint the area where reconnection happens in the tail, about 85,000 to 96,000 miles (140,000 to 160,000 kilometers) downwind of the Earth. They have also been able to show that reconnection frequently occurs in the tail shortly before auroras and magnetic disturbances begin in Earth's atmosphere. Nishida and colleagues interpret those results to mean that reconnection is the source of energy behind the auroras and storms.
The International Solar-Terrestrial Physics program is a joint scientific study between NASA, ISAS, and the European Space Agency (ESA), with contributions from Russia's Institute for Space Research and many other international science institutions. The primary spacecraft of ISTP include ISAS's Geotail, NASA's Polar and Wind spacecraft, and the joint ESA/NASA Solar and Heliospheric Observatory (SOHO).
For images and background information, refer to:
http://www-istp.gsfc.nasa.gov/istp/news/0005/
NASA and NOAA satellites show that the Antarctic ozone thinning covers the largest expanse of territory since the depletion developed in the early 1980s. The measurements were obtained this year between mid-August and early October using the Total Ozone Mapping Spectrometer (TOMS) instrument aboard NASA's Earth Probe (TOMS-EP) satellite and the Solar Backscatter Ultraviolet Instrument (SBUV) aboard the NOAA-14 satellite.
"This is the largest Antarctic ozone hole we've ever observed, and it's nearly the deepest," said Dr. Richard McPeters, Principal Investigator for Earth Probe TOMS.
Preliminary data from the satellites show that this year's ozone depletion reached a record size of 10.5 million square miles (27.3 million square kilometers) on Sept. 19, 1998. The previous record of 10.0 million square miles was set on Sept. 7, 1996.
The ozone level fell to 90 Dobson units on Sept. 30, 1998. This nearly equals the lowest value ever recorded of 88 Dobson Units seen on Sept. 28, 1994, over Antarctica.
Scientists are not concerned that the hole might be growing because they know it is a direct result of unusually cold stratospheric temperatures, though they do not know why it is colder this year. The decrease in ozone, however, could result in more acute solar or ultraviolet radiation exposure in southern Chile and Argentina if the ozone hole were to pass over that region. One of the primary concerns with an ozone hole of this size is that as the hole "breaks up," the ozone-depleted air will diffuse and reduce the overall ozone levels in the mid-latitudes of the southern hemisphere.
These ozone losses are caused by chlorine and bromine compounds released by chlorofluorocarbons (CFCs) and halons. Year-to-year variations of size and depth of the ozone hole depend on the variations in meteorological conditions. Scientists believe that the decrease in Antarctic ozone is attributed to unusually cold (by 5-9 degrees Fahrenheit) temperatures in the southern middle and polar latitudes. "This year was colder than normal and therefore enables greater activation of reactive chlorine that ultimately causes more ozone loss and lower ozone levels," said Dr. Alvin J. Miller of the National Centers for Environmental Prediction (NCEP).
This decrease in ozone was observed earlier than usual with the hole opening in mid-August about two weeks before a typical year. This is consistent with expectations, since chlorine levels have slightly increased since the early 1990s.
As a result of international agreements known as the Montreal Protocol on ozone-depleting substances (and its amendments), chlorine levels from CFCs already have peaked in the lower atmosphere and should peak in the Antarctic stratosphere within a few years. As we move into the next century, chlorine-catalyzed ozone losses resulting from CFCs and other chlorine-containing species will be reduced.
"An ozone hole of substantial depth and size is likely to continue to form for the next few years or until the stratospheric chlorine amount drops to its pre-ozone hole values," said Dr. Paul Newman at NASA's Goddard Space Flight Center (GSFC), Greenbelt, MD. "The decrease in chlorine in our atmosphere is analogous to using a small air cleaner to recycle all of the air in a large indoor sports stadium -- it will take a very, very long time."
Scientists and others have a keen interest in ozone depletion, given that the increased amounts of ultraviolet radiation that reach the Earth's surface because of ozone loss have the potential to increase the incidence of skin cancer and cataracts in humans, harm some crops, and interfere with marine life.
NASA and NOAA instruments have been measuring Antarctic ozone levels since the early 1970s. Since the discovery of the ozone hole in 1985, TOMS and SBUV have been key instruments for monitoring ozone levels over the Earth.
Analysis of TOMS and SBUV data have traced in detail the annual development of the Antarctic "ozone hole," a large area of intense ozone depletion that occurs between late August and early October. Analysis of the historical data indicated that the hole has existed since at least 1979.
A Dobson unit measures the physical thickness of the ozone layer at the pressure of the Earth's surface. The global average ozone layer thickness is 300 Dobson units, which equals three millimeters or 1/8th of an inch, and while not uniform, averages the thickness of two stacked pennies. In contrast during these annual occurrences, the ozone layer thickness in the ozone hole is about 100 Dobson units (1/25th of an inch or 1 millimeter thick), approximately the thickness of a single dime.
Ozone shields life on Earth from the harmful effects of the Sun's ultraviolet radiation. The ozone molecule is made up of three atoms of oxygen; ozone comprises a thin layer of the atmosphere which absorbs harmful ultraviolet radiation from the Sun. Most atmospheric ozone is found in a thin layer between 6-18 miles up.
TOMS ozone data and pictures are available on the Internet at the following URL:
http://toms.gsfc.nasa.gov
or through links at URL:
http://pao.gsfc.nasa.gov/
TOMS-EP and other ozone-measurement programs are key parts of a global environmental effort of NASA's Earth Science enterprise, a long-term research program designed to study Earth's land, oceans, atmosphere, ice and life as a total integrated system. Goddard developed and manages the operation of the TOMS-EP for NASA's Office of Earth Science, Washington, DC.
See the movie at http://svs.gsfc.nasa.gov/~gshirah/toms/
NASA and NOAA satellites show that the Antarctic ozone thinning covers the largest expanse of territory since the depletion developed in the early 1980s. The measurements were obtained this year between mid-August and early October using the Total Ozone Mapping Spectrometer (TOMS) instrument aboard NASA's Earth Probe (TOMS-EP) satellite and the Solar Backscatter Ultraviolet Instrument (SBUV) aboard the NOAA-14 satellite.
"This is the largest Antarctic ozone hole we've ever observed, and it's nearly the deepest," said Dr. Richard McPeters, Principal Investigator for Earth Probe TOMS.
Preliminary data from the satellites show that this year's ozone depletion reached a record size of 10.5 million square miles (27.3 million square kilometers) on Sept. 19, 1998. The previous record of 10.0 million square miles was set on Sept. 7, 1996.
The ozone level fell to 90 Dobson units on Sept. 30, 1998. This nearly equals the lowest value ever recorded of 88 Dobson Units seen on Sept. 28, 1994, over Antarctica.
Scientists are not concerned that the hole might be growing because they know it is a direct result of unusually cold stratospheric temperatures, though they do not know why it is colder this year. The decrease in ozone, however, could result in more acute solar or ultraviolet radiation exposure in southern Chile and Argentina if the ozone hole were to pass over that region. One of the primary concerns with an ozone hole of this size is that as the hole "breaks up," the ozone-depleted air will diffuse and reduce the overall ozone levels in the mid-latitudes of the southern hemisphere.
These ozone losses are caused by chlorine and bromine compounds released by chlorofluorocarbons (CFCs) and halons. Year-to-year variations of size and depth of the ozone hole depend on the variations in meteorological conditions. Scientists believe that the decrease in Antarctic ozone is attributed to unusually cold (by 5-9 degrees Fahrenheit) temperatures in the southern middle and polar latitudes. "This year was colder than normal and therefore enables greater activation of reactive chlorine that ultimately causes more ozone loss and lower ozone levels," said Dr. Alvin J. Miller of the National Centers for Environmental Prediction (NCEP).
This decrease in ozone was observed earlier than usual with the hole opening in mid-August about two weeks before a typical year. This is consistent with expectations, since chlorine levels have slightly increased since the early 1990s.
As a result of international agreements known as the Montreal Protocol on ozone-depleting substances (and its amendments), chlorine levels from CFCs already have peaked in the lower atmosphere and should peak in the Antarctic stratosphere within a few years. As we move into the next century, chlorine-catalyzed ozone losses resulting from CFCs and other chlorine-containing species will be reduced.
"An ozone hole of substantial depth and size is likely to continue to form for the next few years or until the stratospheric chlorine amount drops to its pre-ozone hole values," said Dr. Paul Newman at NASA's Goddard Space Flight Center (GSFC), Greenbelt, MD. "The decrease in chlorine in our atmosphere is analogous to using a small air cleaner to recycle all of the air in a large indoor sports stadium -- it will take a very, very long time."
Scientists and others have a keen interest in ozone depletion, given that the increased amounts of ultraviolet radiation that reach the Earth's surface because of ozone loss have the potential to increase the incidence of skin cancer and cataracts in humans, harm some crops, and interfere with marine life.
NASA and NOAA instruments have been measuring Antarctic ozone levels since the early 1970s. Since the discovery of the ozone hole in 1985, TOMS and SBUV have been key instruments for monitoring ozone levels over the Earth.
Analysis of TOMS and SBUV data have traced in detail the annual development of the Antarctic "ozone hole," a large area of intense ozone depletion that occurs between late August and early October. Analysis of the historical data indicated that the hole has existed since at least 1979.
A Dobson unit measures the physical thickness of the ozone layer at the pressure of the Earth's surface. The global average ozone layer thickness is 300 Dobson units, which equals three millimeters or 1/8th of an inch, and while not uniform, averages the thickness of two stacked pennies. In contrast during these annual occurrences, the ozone layer thickness in the ozone hole is about 100 Dobson units (1/25th of an inch or 1 millimeter thick), approximately the thickness of a single dime.
Ozone shields life on Earth from the harmful effects of the Sun's ultraviolet radiation. The ozone molecule is made up of three atoms of oxygen; ozone comprises a thin layer of the atmosphere which absorbs harmful ultraviolet radiation from the Sun. Most atmospheric ozone is found in a thin layer between 6-18 miles up.
TOMS ozone data and pictures are available on the Internet at the following URL:
http://toms.gsfc.nasa.gov
or through links at URL:
http://pao.gsfc.nasa.gov/
TOMS-EP and other ozone-measurement programs are key parts of a global environmental effort of NASA's Earth Science enterprise, a long-term research program designed to study Earth's land, oceans, atmosphere, ice and life as a total integrated system. Goddard developed and manages the operation of the TOMS-EP for NASA's Office of Earth Science, Washington, DC.
Monserrat volcano:
http://www.geo.mtu.edu/volcanoes/west.indes/soufriere/goft/
General information on volcanoes:
http://volcano.und.edu/
Includes a list of recent eruptions and all the eruptions that have killed more
than 500 people!
Historical volcanoes:
http://www.aist.go/jp/GSJ/~jdehn/v-home.htm
NASA's Observatorium is a public access site for Earth and space data.
View of the Earth from the NEAR spacecraft as it passed the Earth in January 1998 along with earlier views of the asteroid Mathilde are available.
