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Contents Our peculiar planetThe busy landWater and iceOzone holesThe stormy SunClimate changeNatural disastersCosmic impactsServices Subscribe
|  | | | | | | Protecting the Environment
Our planet is a spaceship that for billions of years has carried its precious cargo of life through the dangerous deserts of cosmic space. While anxiety grows about human pressures on the Earth, spacecraft now give an unprecedented chance to understand the planet better. They help to reveal the Earth’s origins and history, to observe natural and manmade global change, and to assess external influences - including the ever-changing Sun and the threat of asteroid impacts. ESA’s programmes of Solar System science, Earth science and environmental monitoring all contribute to the factual knowledge needed for looking after our spaceship properly.
| | SMART-1 | |
Our peculiar planet
Why is the Earth so unlike its sister planets, and oddly fertile? ESA’s Rosetta cometary mission (2004) will examine the raw materials from which the Sun's family of planets was built once it reaches its destination around 2014. Mars Express, launched in 2003, and BepiColombo (2013) will investigate why Mars and Mercury are very different from the Earth, despite their common origin. The idea that the Earth was altered by a huge collision, which created the Moon, was tested since 2003 by the lunar spacecraft SMART-1, which ended its mission in September 2006 with a planned dive onto the Moon's surface. While by measuring regional gravity far more accurately than ever before, ESA’s GOCE satellite (2007) will reveal the internal machinery that renews the Earth’s distinctively fresh surface.
| | | Deforestation in Rondonia, Brazil |
The busy land
Farms and wildlife, cities and industries, roads and rivers - all co-exist uneasily in crowded landscapes. On ESA’s Earth Watch satellites (ERS since 1991 and Envisat from 2002) an imaging radar SAR penetrates the clouds and reveals land use. Comparisons of SAR images from different dates detect changes in the land surface. A visible-infrared scanning radiometer gauges vegetation growth and also measures surface temperatures, often a symptom of land use, and reveals fires used to clear fields. A satellite now under study by ESA, called SMOS, would improve measurements of soil moisture, which is the key to the land’s fertility.
| | Surface winds around Antarctica | |
Water and ice
The watch kept on the oceans from space since 1991, by ESA's ERS, continues with Envisat (2002). The satellite measures sea-level changes and surface temperatures, and observes seasonal growth of plankton, while the role of ERS in gauging ocean winds (by radar scatterometer) will pass to the new weather satellite MetOp, which launched on 19 October 2006. Detection of variations in the thickness of the Greenland and Antarctic ice sheets, pioneered with the ERS radar altimeter, will be improved with twin radars on ESA's Cryosat-2 (2009). Gravity measurements by the Earth Explorer satellite GOCE (2007) promise better knowledge of ocean currents.
| | | ERS-2/GOME map of ozone thinning over Europe |
Ozone holes
Thinning of the stratospheric ozone layer, first conspicuous as a 'hole' over Antarctica, is now apparent also in the north, and the response to curbs on manmade emissions of ozone-harming chemicals is slower than expected. ESA joined in the worldwide effort to measure ozone and study its chemistry with the GOME instrument in ERS-2 (1995). An improved version, SCIAMACHY, is carried on Envisat. Two other instruments detect ozone and other chemicals in the atmosphere seen on the limb (edge) of the Earth from Envisat's viewpoint, by their absorption of starlight (GOMOS) and their emission of infrared signatures (MIPAS).
| | A solar eruption | |
The stormy Sun
Although 150 million kilometres away, the Sun is the most important feature of the Earth’s environment - the source of warmth and the power supply of green plants. ESA has taken an important lead in solar science, with six spacecraft built in Europe for joint missions with NASA. Ulysses (1990), SOHO (1991) and Cluster (4 satellites, 2000) all make unique contributions to global efforts to understand the causes and consequences of the great storms that rack the Sun and disturb the Earth’s space environment. They threaten harm to astronauts, spacecraft, power supplies and computers, and affect the Earth’s climate too.
| | | Cloud climatology |
Climate change
ERS and Envisat watch out for symptoms of climate change in ice cover, sea level and sea-surface temperatures. Archives going back to 1977, from the Meteosat weather satellites developed by ESA, can play a part, in revealing changes in cloud cover and other atmospheric features. The SOHO spacecraft records variations in the Sun’s brightness. Manmade greenhouse gases arouse international concern as a cause of global warming, yet effects predicted by computer models still differ widely. With a view to narrowing the differences, ESA’s ADM-Aeolus satellite will measure winds at all levels and over all regions, for the very first time.
| | Flooding in Bangladesh | |
Natural disasters
Effects of volcanic eruptions, earthquakes, landslides, windstorms, floods and forest fires are often visible from space. If satellite observations are to be useful in management of the resulting emergencies, they must be available instantly. ESA’s REMSAT project (Real Time Emergency Management via Satellite) integrates satellite observations with the use of telecommunications and navigation satellites in a generic system that could be used anywhere else in the world to manage the response to any large natural (or manmade) disaster. A long-term aim is to widen the scope of early warnings from space, already available in the case of hurricanes.
| | | Comparative sizes of asteroids |
Cosmic impacts
In the past, asteroids and comets have often collided with the Earth, without warning, causing regional or global disasters. Impacts may be predictable in future, or even averted. Spaceguard, sponsored by ESA, coordinates 80 asteroid-hunting centres worldwide. Telescopes in space will accelerate the detection of near-Earth objects. ESA’s Gaia mission will find dozens as a by-product of mapping the billion brightest stars in the sky, while BepiColombo, orbiting Mercury, will have a special view of asteroids inside the Earth’s orbit. Inspections of asteroids and comets at close range give a better understanding of the physical threat - tasks for ESA’s Rosetta mission.
Last update: 24 October 2006 | |
| | Related links ESA's Science websiteObserving the EarthOzone forecastsThe Sun nowESA's Living Planet Programme
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