Lost lakes of Titan are found at last

This colorized radar view from Cassini shows lakes on Titan. Color intensity is proportional to how much radar brightness is returned. The colors are not a representation of what the human eye would see. Image credit: NASA/JPL/USGS

Lakes of methane have been spotted on Saturn's largest moon, Titan, boosting the theory that this strange, distant world bears beguiling similarities to Earth, according to a new study.

Titan has long intrigued space scientists, as it is the only moon in the Solar System to have a dense atmosphere -- and its atmosphere, like Earth's, mainly comprises nitrogen.

Titan's atmosphere is also rich in methane, although the source for this vast store of hydrocarbons is unclear.

Methane, on the geological scale, has a relatively limited life. A molecule of the compound lasts several tens of millions of years before it is broken up by sunlight.

Given that Titan is billions of years old, the question is how this atmospheric methane gets to be renewed. Without replenishment, it should have disappeared long ago.

A popular hypothesis is that it comes from a vast ocean of hydrocarbons.

But when the US spacecraft Cassini sent down a European lander, Huygens, to Titan in 2005, the images sent back were of a rugged landscape veiled in an orange haze.

There were indeed signs of methane flows and methane precipitation, but nothing at all that pointed to any sea of the stuff.

But a flyby by Cassini on July 22 last year has revealed, thanks to a radar scan, 75 large, smooth, dark patches between three and 70 kilometers across (two and 42 miles) across that appear to be lakes of liquid methane, scientists report on Thursday.

They believe the lakes prove that Titan has a "methane cycle" -- a system that is like the water cycle on Earth, in which the liquid evaporates, cools and condenses and then falls as rain, replenishing the surface liquid.

As on Earth, Titan's surface methane may well be supplemented by a "table" of liquid methane that seeps through the rock, the paper suggests.
Some of the methane lakes seem only partly filled, and other depressions are dry, which suggests that, given the high northerly latitudes where they were spotted, the methane cycle follows Titan's seasons.
In winter, the lakes expand, while in summer, they shrink or dry up completely -- again, another parallel with Earth's hydrological cycle.
The study, which appears on Thursday in the British weekly journal Nature, is headed by Ellen Stofan of Proxemy Research in Virginia and University College London.
Titan and Earth are of course very different, especially in their potential for nurturing life. Titan is frigid, dark and, as far as is known, waterless, where as Earth is warm, light and has lots of liquid water.
But French astrophysicist Christophe Sotin says both our planet and Titan have been sculpted by processes that, fundamentally, are quite similar.
The findings "add to the weight of evidence that Titan is a complex world in which the interaction between the inner and outer layers is controlled by processes similar to those that must have dominated the evolution of any Earth-like planet," Sotin said in a commentary.
"Indeed, as far as we know," Sotin added, "there is only one planetary body that displays more dynamism than Titan. Its name is Earth."

(c) www.physorg.com

India to test space capsule as part of moon mission

India plans to launch a capsule into orbit early next year and bring it back to Earth, an initial step towards an unmanned mission to the moon by 2010, a news report said Sunday.

The Indian Space Research Organisation (ISRO), which has said it hopes to send an unmanned probe to the moon in the next three years, has said it needs to test its re-entry and recovery technology, the Indian Express report said.

The agency will launch a 50-kilogram (110 pound) capsule and then have it re-enter and splash into the Bay of Bengal after 15 to 30 days of orbit around the Earth, the newspaper said.

The announcement is the latest by India's space agency that show an expansion in policy from projects meant to aid national development to a growing interest in space exploration, the report said.

The space agency also said last month that it planned to send an unmanned mission to Mars by 2013 to look for evidence of life.

The six-to-eight-month mission, would cost three billion rupees (67 million dollars), the Hindustan Times reported.

© 2006 AFP

(c) www.physorg.com

Space shuttle Discovery completes successful ISS mission

Space shuttle Discovery and its seven-member crew has landed in Florida after a 13-day mission that advanced construction of the International Space Station.

Discovery touched down at 2232 GMT on the landing strip at the Kennedy Space Center, near Cape Canaveral, where it had lifted off in a nighttime launch on December 9.

"You have seven thrilled people here," shuttle commander Mark Polansky said just after landing.

A controller at the Mission Control Center in Houston, Texas, replied: "Congratulations on what was probably the most complex assembly mission of the Station to date."

The Discovery astronauts spent eight days at the International Space Station (ISS), continuing the construction of the orbiting laboratory by attaching a two-tonne truss to its girder-like structure in the first of four space walks.

During the next two space walks, they rewired the station's power system and put it on a permanent basis.

A fourth space walk was added Monday to shake loose a solar array panel that had gotten stuck as it was being folded.

"It was a wonderful end to a great mission," Michael Griffin, a NASA administrator, said at a news conference at Kennedy Space Center where he welcomed the astronauts after they left the spacecraft.

"The crew on orbit and the crew on the ground could not have done better," he said.

The shuttle's return to Earth initially was scheduled Thursday but the mission was extended a day to allow for the unplanned space walk.

Poor weather conditions in Florida had scotched an earlier scheduled landing Friday and National Aeronautics and Space Administration officials had considered bringing the shuttle down at alternative sites.

A decision to land at Kennedy was made only at the last minute and "it turned out to be a great one," Griffin said.

NASA officials had hoped weather conditions would improve enough in Florida to avoid having to land the space shuttle at Edwards Air Force Base in California or White Sands Space Harbor in New Mexico.

A landing at either location in the western United States would have meant NASA would have to fly the shuttle to Florida, in the southeast, on the back of a modified Boeing 747 plane, which would cost some 1.7 million dollars.

The shuttle plunged at more than 26,500 kilometers (16,500 miles) an hour as it descended through the Earth's atmosphere, triggering a double sonic boom as it lowered through the skies above the runway on Florida's Atlantic coast.

On board were six US astronauts and one from the European Space Agency (ESA), Christer Fuglesang, Sweden's first astronaut.

After this mission, NASA plans at least 13 more shuttle flights -- including five in 2007 -- to complete construction of the International Space Station by 2010, when the three-spacecraft shuttle fleet is due to be retired.

ISS construction fell years behind schedule after the 2003 Columbia tragedy when the spacecraft disintegrated minutes ahead of landing, killing all seven astronauts aboard.

NASA suspended the shuttle program to deal with safety problems. The space shuttle Atlantis mission in September marked the resumption of ISS construction.

Discovery carried astronaut Sunita Williams to the ISS, where she will remain for six months. Williams replaced Thomas Reiter, a German ESA astronaut who had been on the station since July and who returned on Discovery.

(c) www.physorg.com

Secret Worlds: The Universe Within

  

View the Milky Way at 10 million light years from the Earth. Then move through space towards the Earth in successive orders of magnitude until you reach a tall oak tree just outside the buildings of the National High Magnetic Field Laboratory in Tallahassee, Florida. After that, begin to move from the actual size of a leaf into a microscopic world that reveals leaf cell walls, the cell nucleus, chromatin, DNA and finally, into the subatomic universe of electrons and protons.

Notice how each picture is actually an image of something that is 10 times bigger or smaller than the one preceding or following it. The number that appears on the lower right just below each image is the size of the object in the picture. On the lower left is the same number written in powers of ten, or exponential notation. Exponential notation is a convenient way for scientists to write very large or very small numbers. For example, compare the size of the Earth to the size of a plant cell, which is a trillion times smaller:

Earth = 12.76 x 10⁺⁶ = 12,760,000 meters wide
(12.76 million meters) Plant Cell = 12.76 x 10^-6 = 0.00001276 meters wide
(12.76 millionths of a meter)  

Scientists examine things in particular ways using a combination of very sophisticated equipment, everyday instruments, and many unlikely tools. Some phenomena that scientists want to observe are so tiny that they need a magnifying glass, or even a microscope. Other things are so far away that a powerful telescope must be used in order to see them. It is important to understand and be able to compare the size of things we are studying. To learn more about the relative sizes of things, visit our Perspectives: Powers of 10 activity site.

(C) www.micro.magnet.fsu.edu

Planets Were Formed From A Giant Mix, Suggests New Analysis

 

Our Solar System may have been created in a gigantic mixing process far more extensive than previously imagined, according to research published today.

The findings, reported in the journal Science, come from the first analysis of dust fragments from Comet Wild-2, captured by NASA's Stardust spacecraft and brought to Earth in January 2006. Because comets are among the oldest objects in the Solar System, the team, which includes researchers from Imperial College London and the Natural History Museum, believes their sample of dust can provide insights into how Earth and other planets came to be formed.

Using spectroscopy technology which does not damage the mineral content of the particles, the team found that the comet dust is made up of many different mineral compositions rather than a single dominant one. This implies that the dust was formed in many different environments before coming together to make the comet, indicating a great deal of mixing in the early Solar System prior to the formation of planets.

Particularly significant was the discovery of calcium aluminium inclusions, which are amongst the oldest solids in the Solar System and are thought to have formed close to the young Sun. This discovery suggests that components of the comet came from all over the early Solar System, with some dust having formed close to the Sun and other material coming from the asteroid belt between Mars and Jupiter. Since Wild-2 originally formed in the outer Solar System, this means that some of its composite material has travelled great distances. Dr Phil Bland of Imperial's Department of Earth Science and Engineering says:

"We weren't expecting to find such widely-spread material in the sample of dust we were given to examine. The composition of minerals is all over the place, which tells us that the components that built this comet weren't formed in one place at one time by one event. It seems that the Solar System was born in much more turbulent conditions than we previously thought."

The researchers have also found evidence of surprising variety in cometary composition. NASA's 2005 Deep Impact mission, which provided images of material blasted from the nucleus of the comet Tempel 1, revealed evidence of aqueous activity within the comet. However the dust from Wild-2 has none of those characteristics and apparently has not interacted with water at all. Anton Kearsley of the Natural History Museum says:

"This is a very interesting mismatch, and it seems that comets are not all the same. Perhaps they vary as much in their evolution as in the composition of the dust from which they are made."

This is the first time scientists have had the opportunity to study samples from a comet, having previously relied on studying comets from afar or analysing interplanetary dust particles of uncertain origin. Dr Bland adds:

"Comets are likely to be the oldest objects in our Solar System and their components have remained largely unchanged, so discovering more about what they have experienced gives us a snapshot of the processes that formed the planets over four and a half billion years ago. Fundamentally we still don't know how you make planets from a cloud of dust and gas. Hopefully the Wild-2 samples will help us towards an answer."

The analysis was carried out by the Impacts and Astromaterials Research Centre, a joint Imperial-Natural History Museum research group funded by the Particle Physics and Astronomy Research Council.

[Thanks goes to www.sciencedaily.com for this article]

Global Warming Affects Space Station Orbit

By Robert Roy Britt
LiveScience Managing Editor

As the climate warms near Earth's surface, the upper atmosphere is getting less dense, a change that will mean less drag on satellites, scientists announced today.

Carbon dioxide emissions from the burning of fossil fuels will cause a 3 percent reduction in air density in the outermost layer of the atmosphere by 2017, the researchers predict.

Among the affected satellites: The International Space Station and the Hubble Space Telescope.

"We're seeing climate change manifest itself in the upper as well as lower atmosphere," said Stan Solomon of the National Center for Atmospheric Research (NCAR). "This shows the far-ranging impacts of greenhouse gas emissions."

• Video: How it Works

The finding was presented today at a meeting of the American Geophysical Union in San Francisco.

The thermosphere extends from about 60 miles above Earth to 400 miles. The air is incredibly thin, but still causes drag on satellites in low Earth orbit. NASA routinely boosts the orbit of the space station as it is constantly degrading. Other satellites have limited life spans in part because the thin air up there eventually drags them down.

A thinning thermosphere means satellites can stay aloft longer.

Carbon dioxide molecules absorb radiation. Near Earth's surface, the molecules collide frequently with other molecules and the energy is released as heat, warming the air, the scientists explained. In the much thinner thermosphere, a carbon dioxide molecule has ample time to radiate energy to space because collisions are infrequent. The result is a cooling effect. And as it cools, the thermosphere settles, so that the density at a given height is reduced.

• Video: The Greenhouse Effect

The effect varies with changes in the 11-year cycle of the Sun's activity, too. Being able to now predict the changes will help satellite operators plan better, the researchers said.

"Satellite operators noticed the solar cycle changes in density at the very beginning of the Space Age," Solomon said. "We are now able to reproduce the changes using the NCAR models and extend them into the next solar cycle."

The findings are also detailed in the journal Geophysical Research Letters and explained in a video presentation.

[original post: www.livescience.com]