ESA Envisat: Earth from Space: Historical view

West Africa’s coast along the Atlantic Ocean is pictured in this first image from Envisat’s MERIS instrument nearly a decade ago.

This week, Envisat celebrated ten years in orbit. The Medium Resolution Imaging Spectrometer (MERIS) on board the satellite was developed to measure sea colour in oceans and coastal areas, although it has been used for a variety of additional applications over the years.

Happy Birthday ESA's ENVISAT (Video)

Envisat carries ten sensors, collecting imagery and other data on Earth’s land, oceans, atmosphere, temperature and ice cover.

The first batch of data from the satellite in March 2002 was acquired via the Kiruna station in Sweden and processed at ESA’s ESRIN establishment in Italy and other centres throughout Europe.

In this first image from MERIS on 22 March 2002, a very dry desert directly borders the ocean teeming with life. To the south, a high concentration of phytoplankton was detected along the coasts of Senegal, the Gambia and Guinea-Bissau.

Small, single-celled phytoplankton play a key role in the marine food chain. They convert sunlight, carbon dioxide and nutrients into carbohydrates on which nearly all life in the ocean depends.

In most parts of Earth’s oceans, phytoplankton concentration is extremely low. However, in ‘upwelling areas’ like the one pictured here, the ocean becomes rich in minerals from the mixing of surface waters with deeper waters.

The most important fishing grounds can be found in these upwelling areas. Climate change has an effect on the intensity and geographical position of these areas, which, in turn, has important consequences for the fishing industries and those who depend on them.

Also evident in this image is the transition from the dry desert lands in the north through the savannah and to tropical vegetation in the south, which receives more rainfall. MERIS can monitor land use that leads to increased erosion and soil loss.

The Image of the Week is featured on ESA Web-TV, broadcast online every Friday at 10:00 CET.

ESA ISS Image: Manicouagan impact crater, Quebec

From warm Pacific to the cold plains of Canada in 30 minutes. Manicouagan impact crater, Quebec.

Andre Kuipers looks down on the Manicougan impact crater in Canada from his vantage point onboard the International Space Station.

Credit: ESA/NASA

NASA Spitzer Telescope Image: Hidden Jet

Spitzer Image HH-34

NASA's Spitzer Space Telescope took this image of a baby star sprouting two identical jets (green lines emanating from fuzzy star).

The jet on the right had been seen before in visible-light views, but the jet at left, the identical twin to the first jet, could only be seen in detail with Spitzer's infrared detectors (IRAC).

The left jet was hidden behind a dark cloud, which Spitzer can see through.



The twin jets, in a system called Herbig-Haro 34 (HH-34), are made of identical knots of gas and dust, ejected one after another from the area around the star.

By studying the spacing of these knots, and knowing the speed of the jets from previous studies, astronomers were able to determine that the jet to the right of the star punches its material out 4.5 years later than the counter-jet.

Hubble Images

The new data also reveal that the area from which the jets originate is contained within a sphere around the star, with a radius of 3 astronomical units.

An astronomical unit is the distance between Earth and the sun. Previous studies estimated that the maximum size of this jet-making zone was 10 times larger.

The wispy material is gas and dust. Arc-shaped bow shocks can be seen at the ends of the twin jets. The shocks consist of compressed material in front of the jets.

The Herbig-Haro 34 (HH-34) jets are located at approximately 1,400 light-years away in the Orion constellation.

Image Credit: NASA/JPL-Caltech

NASA - Spray Bars to Help Test Engine Icing

Ron Colantonio (left), manager of the Atmospheric Environment Safety Technologies Project at NASA’s Glenn Research Center in Cleveland, discussed with NASA Administrator Charlie Bolden the latest testing and research on airplane engine icing during the administrator's February 2012 visit to the center.

Colantonio showed Bolden how a large horizontal array of spray bars, such as those pictured, would emit a cloud of ice crystals in high-altitude, low pressure conditions that match those an airliner might experience in flight.

NASA scientists are mounting a research campaign using flight and ground tests to solve this aviation mystery, in which ice crystals associated with warm-weather storms can be ingested into the core of a hot jet engine, melt and then re-freeze.

As larger amounts of ice build up, some of the ice can break off and cause damage inside the engine, or melt and cause the engine to lose power or shut down altogether in a flameout.

Part of the research effort involves using the spray bars to simulate the icing conditions in engines on the ground at the Propulsion Systems Laboratory at Glenn. Eventually, a full-scale engine will be mounted opposite the bar array.

Image Credit: NASA/Marvin Smith

NASA MARS Orbiter: Tenth Anniversary Image from THEMIS

The Thermal Emission Imaging System (THEMIS) camera on NASA's Mars Odyssey spacecraft has completed an unprecedented full decade of observing Mars from orbit.

THEMIS captured this image on Feb. 19, 2012, 10 years to the day after the camera recorded its first view of Mars.

This image covers an area 11 by 32 miles (19 by 52 kilometers) in the Nepenthes Mensae region north of the Martian equator.

The view depicts a knobby landscape where the southern highlands are breaking up as the terrain descends into the northern lowlands.

Odyssey, launched in 2001, has worked at Mars longer than any mission in history.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Mars Odyssey mission for NASA's Science Mission Directorate, Washington.

THEMIS was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing.

For more information about Mars Odyssey, visit mars.jpl.nasa.gov/odyssey . For more about THEMIS, see themis.asu.edu/ .

Image credit: NASA/JPL-Caltech/ASU

A bad day on Venus gets even worse

Contrary to its alluring name, Venus is the planet from hell, with an atmosphere so hot, toxic and heavy that any visitor would risk being simultaneously melted, suffocated and crushed.

But not just that: the second planet from the Sun turns on its axis so slowly that, for any survivor, a Venusian day would seem interminable, for it is the equivalent of 243 days on Earth.

To make things worse, a day on Venus is getting even longer, French astronomers have discovered.

A team from the Paris Observatory analysed data from a spectrometer aboard a European orbiter, the Venus Express.

Called VIRTIS, the gadget measures infrared and visible light and is used to scan the planet's surface beneath the thick, roiling atmosphere.

The astronomers were stunned when they checked landmarks against the last mapping of Venus, carried out between 1990 and 1994 by the US probe Magellan.

At a given point in the Venusian day, landmarks were a full 20 kilometers (12 miles) behind where they should have been.

The team, publishing in the journal Icarus, say they have been over the observations again and again.

"After eliminating possible sources of error, we believe that the duration of the Venusian day must have changed over the 16 years," they said in a press release.

Their calculation is that an extra six and a half terrestial minutes have been added to the Venusian day during this time.

"On the astronomical scale, this is a major change," said VIRTIS investigator Pierre Drossart.

Pierre Drossart is depicted here in an ESA Video on the Venus Express, along with his ESA collegues, explaining the thinking behind the Venus Express mission.

The astronomers' hypothesis is that friction by Venus' atmosphere is braking the movement of the terrain below.

That sounds bizarre until one realises that the atmosphere is 100 kms (60 miles) thick, with extremely dense clouds of 96 percent carbon dioxide, driven by superwinds reaching some 350 kilometres (210 miles) per hour.

Atmospheric pressure at the surface is 92 times that of Earth -- the equivalent of being more than 900 metres (3,000 feet) below the ocean.

"A braking effect from the atmosphere also occurs erratically on Earth, but the discrepancy is only a matter of a few tenths of a second and it is imperceptible," Drossart told AFP.

So will Venus eventually stop spinning -- or even go into reverse rotation?

"It's difficult to say, given that we only have two points of measurement," said Drossart.

"But theoretical models suggest that this is probably just a cyclical phenomenon. If the atmosphere speeds up, the planet slows. Then the energy goes into reverse, in a pendulum effect."

Asteroid 2011 AG5: A Reality Check

Asteroid 2011 AG5 has been receiving a lot of attention lately because of a very unlikely scenario which would place it on an Earth-interception course 28 years from now.

Here is a scientific reality check of this relatively nondescript space rock which is currently ranked a "1" on the 1 to 10 Torino Impact Hazard Scale

As of Feb. 26, 2012, asteroid 2011 AG5 is one of 8,744 near-Earth objects that have been discovered.

It is approximately 460 feet (140 meters) in size and its orbit carries it as far out as beyond Mars' orbit and as close to the sun as halfway between Earth and Venus.

It was discovered on Jan. 8, 2011, by astronomers using a 60-inch Cassegrain reflector telescope located at the summit of Mount Lemmon in the Catalina Mountains north of Tucson, Arizona.

Due to its current location in the daytime sky, observations of 2011 AG5 cannot be made by Earth-based telescopes, so its orbit has not yet been determined to a level where scientists can confidently project its location decades into the future. But that day is coming.

"In September 2013, we have the opportunity to make additional observations of 2011 AG5 when it comes within 91 million miles (147 million kilometers) of Earth," said Don Yeomans, manager of NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif.

"It will be an opportunity to observe this space rock and further refine its orbit. Because of the extreme rarity of an impact by a near-Earth asteroid of this size, I fully expect we will be able to significantly reduce or rule out entirely any impact probability for the foreseeable future."

Even better observations will be possible in late 2015.