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Earth Perspectives : Feature Articles NASA Earth Observatory Home● Image of the Day Feature Articles News Natural Hazards Global Maps Search Earth Perspectives by Holli Riebeek November 4, 2008 NASA astronaut photograph AS10-34- Say NASA, and many images may come to mind:5036. a white-clad man leaping awkwardly, joyfully across the surface of the moon; probes gliding into the depths of the solar system, sending back pictures● by Holli of Riebeekdistant worlds; two tenacious robots exploring the red rock surface● design of Mars, by Robert uncovering Simmon evidence of a wet past; the horrifying disintegration of the● November Challenger 24, and 2008 Columbia space shuttles. For some, another image comes to mind: a tiny blue and white planet, a fragile oasis in the black vastness of space. Recalling his thoughts while orbiting the Moon during the landmark Apollo 8 mission, astronaut Bill Anders said, “We came all this way to explore the Moon, and the most important thing is that we discovered the Earth.” (Quoted in The Societal Impact of Space Flight, p.55.) Venturing into space has taught us about our Sun, solar system, and the universe beyond, but it has also given us a new perspective on our home planet, Earth. In 2008, as NASA celebrates 50 years of existence as an agency and 40 years since man first left Earth’s orbit, the Earth Observatory asked a number of Earth scientists what unique insights space flight has given us about Earth. Some emphasized revolutionary technology, others mentioned specific discoveries and observations of important Earth events, while others highlighted the power of http://earthobservatory.nasa.gov/Features/EarthPerspectives/printall.php (1 of 23)2008.11.26 9:31:13 AM Earth Perspectives : Feature Articles satellite images to make us understand the interconnectedness of people and places around the globe. A selection of their responses follows. Piers Sellers Biospheric scientist and astronaut Piers Sellers remembers admiring the intricate details visible from the orbiting space shuttle. “It was like someone spent forever building a tiny model.” He was surprised by the thinness of the atmosphere, a delicate mist glued to Earth’s surface, and delighted in seeing the edges of the clouds curl up towards space, something that isn’t obvious in two dimensional satellite images. Astronauts and cosmonauts have Apart from letting humanity see Earth differentlytaken thanthousands ever before, of photographs the view offrom space has also expanded our understanding theof how Earth, the including planet works, Mt. Everest and just (left), in time to grasp the impact humanity is havingCuba on the (center), planet andand itsclouds climate over system, South says Sellers. For the first time, we see our planet as a whole, a system of America (right). (NASA astronaut intricately connected parts that interact—and can be perturbed—in ways humans photographs ISS008-E-6146, ISS017- had not previously glimpsed. For example, the view from space was necessary to E-14060, and ISS017-E-13859.) understand how much carbon moves through ocean and land plants every year during photosynthesis, says Sellers. “You need a global view to understand global processes like the carbon cycle.” Global measurements of the carbon stored by plants (net primary productivity) during photosynthesis are an important piece of the climate change puzzle. Scientists need to know how much of the carbon dioxide http://earthobservatory.nasa.gov/Features/EarthPerspectives/printall.php (2 of 23)2008.11.26 9:31:13 AM Earth Perspectives : Feature Articles released by burning fossil fuels the biosphere can absorb and how much will linger in the atmosphere. (NASA map by Robert Simmon and Reto Stöckli, based on MODIS data.) Moustafa T Chahine AIRS/Aqua Science Team Leader, Senior Research Scientist NASA’s Jet Propulsion Laboratory We view Earth now as a planet, not unlike Mars or Venus. Prior to the advent of space exploration, we could only look at the planets from a great distance but now robotic spacecraft like rovers and landers are enabling us to observe them up close. For Earth it was quite the opposite. Heretofore, we could only observe our immediate surroundings like lands, oceans, clouds, mountains, etc. The view from space allows us to observe the entire Earth as a planet. Scientifically, NASA initiated the concept of “Earth System Science” to describe that the Earth’s climate system is an interactive system with many feedbacks [connections]. What happens in one part affects the rest. NASA went on to collect individual measurements like sea surface temperature, outgoing radiation, soil moisture, etc. and integrated measurements from different sounders and imagers to study the feedbacks among the various individual measurements. My favorite image of Earth is the composite view of Earth at night, which shows the light over the USA East and West Coasts, Europe, Japan and along the Nile river. It is one of very few space observations that demonstrates “intelligent life exists on our planet.” http://earthobservatory.nasa.gov/Features/EarthPerspectives/printall.php (3 of 23)2008.11.26 9:31:13 AM Earth Perspectives : Feature Articles The view of city lights at night is one Marc Imhoff of very few space observations that Project Scientist for NASA’s Terra satellitedemonstrates “intelligent life exists NASA Goddard Space Flight Center on our planet,” says Moustafa We have come to realize how thin and fragileChahine. our atmosphere On the other is, how hand, finite says our resources are, and how interconnected we areMarc with Imhoff, everyone “nothing else on shows the planet.how Scientifically, the view from space has enabled us to see how human activities much impact we are having as a can interact with natural cycles to cause important changes. For the first time, species on this planet better than that we have observed the melting of ice and sea level rise, and how ocean circulation composite image.” works. (NASA image by Robert Simmon, My favorite view of Earth from space is the global city lights at night. Nothing based on MODIS Blue Marble and shows how much impact we are having as a species on this planet better than Defense Meteorological Satellite that composite image. Program city lights data.) http://earthobservatory.nasa.gov/Features/EarthPerspectives/printall.php (4 of 23)2008.11.26 9:31:13 AM Earth Perspectives : Feature Articles Harrison Schmitt Apollo Astronaut, Geologist As a geologist, my perspective of the Earth as a planet in space did not change with the opportunity to view it on the way to the Moon. But I was impressed by how well I could observe and forecast weather patterns during those three days, with the help of a 10X monocular. The Apollo views of the full Earth disk have stimulated thought on the value of continuous monitoring the full disk from the Moon as inherently different than the views from Earth orbit. Apollo astronauts captured a series of over 700 photographs of the Earth’s disk on their way to and from the moon. A crew member of Apollo 10 snapped this shot while he was 100,000 nautical miles (185,000 kilometers) from Earth on May 18, 1969. (Astronaut Photograph AS10- 34-5026.) Lee-Lueng Fu Senior Research Scientist, Project Scientist for the TOPEX/Poseidon, Jason-1, and OSTM/Jason-2 Missions. NASA Jet Propulsion Laboratory First of all, seeing Earth from space has a psychological impact on human’s awareness of the planet we are all sharing. It heightens our sense of the global http://earthobservatory.nasa.gov/Features/EarthPerspectives/printall.php (5 of 23)2008.11.26 9:31:13 AM Earth Perspectives : Feature Articles impact of both natural processes and human activities. Scientifically, observing Earth from space has revolutionized our understanding of Earth as a system. For the first time we are able to see how the world’s landscape has been changing on a scale not amenable to ground-based observations. We begin appreciating the ocean’s effects on weather on land through dramatic events like El Niño. We are seeing the minute change of global sea level as well as the rapidly disappearing Arctic sea ice as a consequence of global warming. By comparing measurements of topography taken at different times, we can delineate the slow change of the surface of Earth that results from the tectonic movement of Earth’s crust. We are even able to detect the minute change of Earth’s gravity field caused by the melting of ice on Greenland and Antarctica as well as by the seasonal change of ground water on land. El Niño and La Niña are characterized by large-scale changes in equatorial Pacific Ocean currents. The TOPEX/ Poseidon satellite monitored changes in sea-surface height during the record 1997 El Niño and subsequent 1999 La Niña. In October 1997, warm water piled up off the west coast of South America, raising sea level (red), while in March 1999, the cool waters of La Niña dropped the sea level below normal (blue). (Maps by Robert Simmon, based on TOPEX/ Poseidon data from the World Ocean Circulation Experiment.) http://earthobservatory.nasa.gov/Features/EarthPerspectives/printall.php (6 of 23)2008.11.26 9:31:13 AM Earth Perspectives : Feature Articles Viewing Earth from space enabled the following scientific discoveries, not in ranked order and surely biased by my own perspective: ● Direct observations of the ozone hole leading to the understanding of its formation and fluctuations; ● Observations of the fluctuations of sea ice coverage leading to the understanding of its dynamics and relation to global climate change; ● Direct measurement of the change of global mean sea level, showing sea level rise during the last decade at a rate twice that during the preceding 100 years; ● First direct measurement of the effects of change in Earth’s hydrosphere [water systems] and cryosphere [snow and ice] on Earth’s gravity field.

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