Oferte Emag

What is Consuming Hydrogen and Acetylene on Titan?

Copyright NASA

Two new papers based on data from NASA’s Cassini spacecraft scrutinize the complex chemical activity on the surface of Saturn’s moon Titan. While non-biological chemistry offers one possible explanation, some scientists believe these chemical signatures bolster the argument for a primitive, exotic form of life or precursor to life on Titan’s surface. According to one theory put forth by astrobiologists, the signatures fulfill two important conditions necessary for a hypothesized “methane-based life.”

One key finding comes from a paper online now in the journal Icarus that shows hydrogen molecules flowing down through Titan’s atmosphere and disappearing at the surface. Another paper online now in the Journal of Geophysical Research maps hydrocarbons on the Titan surface and finds a lack of acetylene.

This lack of acetylene is important because that chemical would likely be the best energy source for a methane-based life on Titan, said Chris McKay, an astrobiologist at NASA Ames Research Center, Moffett Field, Calif., who proposed a set of conditions necessary for this kind of methane-based life on Titan in 2005. One interpretation of the acetylene data is that the hydrocarbon is being consumed as food. But McKay said the flow of hydrogen [...]

Cassini Returning Enceladus Gravity Data

Copyright NASA/JPL/Space Science Institute

NASA’s Cassini spacecraft successfully completed its 26-hour gravity observation at Saturn’s moon Enceladus this week, sending back data scientists will use to understand the moon’s interior composition and structure.

The flyby took Cassini through the water-rich plume flaring out from Enceladus’ south polar region, with a closest approach of about 100 kilometers (60 miles) occurring in the late afternoon of April 27, 2010, Pacific Time, or just after midnight April 28 UTC.

A steady radio link to NASA’s Deep Space Network on Earth enabled Cassini’s scientists to use the radio science instrument to measure the variations in the gravitational pull of Enceladus. Analyzing the wiggles will help scientists understand whether an ocean, pond or great lake lies under the famous “tiger stripe” fractures that spew water vapor and organic particles from the south polar region.

Results from the experiment will also tell scientists if bubbles of warmer ice in the interior rise toward that region’s surface like an underground lava lamp.

Radio science was prime during the flyby and controlled spacecraft pointing. The optical instruments were not pointed at Enceladus during most of the flyby, so the imaging camera obtained some more distant pictures.

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Flash: NASA’s Cassini Sees Lightning on Saturn

Copyright NASA

NASA’s Cassini spacecraft has captured images of lightning on Saturn. The images have allowed scientists to create the first movie showing lightning flashing on another planet.

After waiting years for Saturn to dim enough for the spacecraft’s cameras to detect bursts of light, scientists were able to create the movie, complete with a soundtrack that features the crackle of radio waves emitted when lightning bolts struck.

“This is the first time we have the visible lightning flash together with the radio data,” said Georg Fischer, a radio and plasma wave science team associate based at the Space Research Institute in Graz, Austria. “Now that the radio and visible light data line up, we know for sure we are seeing powerful lightning storms.”

The movie and radio data suggest extremely powerful storms with lightning that flashes as brightly as the brightest super-bolts on Earth, according to Andrew Ingersoll, a Cassini imaging science subsystem team member at the California Institute of Technology in Pasadena. “What’s interesting is that the storms are as powerful — or even more powerful — at Saturn as on Earth,” said Ingersoll. “But they occur much less frequently, with usually only one happening on the [...]

Prometheus: Over Easy

Copyright NASA/JPL/Space Science Institute

Looking for all intents and purposes like a celestial egg after a session in Saturn’s skillet, Prometheus displayed its pockmarked, irregular surface for NASA’s Cassini spacecraft on Jan. 27, 2010.

Prometheus is one of Saturn’s innermost moons. It orbits the gas-giant at a distance of 139,353 kilometers (85,590 miles) and is 86 kilometers (53 miles) across at its widest point. The porous, icy-bodied world was originally discovered by images taken by Voyager 1 back in 1980. You could say this latest “egg-cellent” view has the Cassini science team licking their chops at the thought of future Prometheus images.

This raw, unprocessed image of Prometheus [pro-MEE-thee-us] , taken in visible light, was obtained by Cassini’s narrow-angle camera at a distance of approximately 36,000 kilometers (23,000 miles).

The Cassini Equinox Mission is a joint United States and European endeavor. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. For more information about the Cassini Equinox Mission visit: http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

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Cassini finding hints at ocean within Saturn’s moon Enceladus

cassini-finding-hints-at-ocean-within-saturns-moon-enceladus

Copyright ESA

European scientists on the joint NASA/ESA Cassini mission have detected, for the first time, sodium salts in ice grains of Saturn’s E-ring, which is primarily replenished by material from the plumes of water vapour and ice grains emitted by Saturn’s moon Enceladus. The detection of salty ice indicates that the little moon harbours a reservoir of liquid water, perhaps even an ocean, beneath its surface. Cassini discovered the water-ice plumes on Enceladus in 2005. These plumes, emitted from fractures near its south pole, expel tiny ice grains and vapour, some of which escape the moon’s gravity, replenishing Saturn’s outermost ring, the E-ring. Cassini’s Cosmic Dust Analyzer, led by Principal Investigator Ralf Srama, of the Max Planck Institute for Nuclear Physics in Heidelberg, Germany, has examined the composition of these grains and found sodium salt (or table salt) within them. “We believe that the salty material deep inside Enceladus washed out from rock at the bottom of a liquid layer,” said Frank Postberg, Cassini scientist on the Cosmic Dust Analyzer at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Postberg is lead author of a study that appears in the 25 June issue of the journal [...]

Ocean may exist beneath Titan's crust

ocean-may-exist-beneath-titans-crust

Copyright ESA

Cassini has discovered evidence that points to the existence of an underground ocean of water and ammonia on Saturn’s moon Titan. The findings were made using radar measurements of Titan’s rotation.

“With its organic dunes, lakes, channels and mountains, Titan has one of the most varied, active and Earth-like surfaces in the solar system,” said Ralph Lorenz, lead author of the paper and Cassini radar scientist at the Johns Hopkins Applied Physics Laboratory in Maryland, USA. “Now we see changes in the way Titan rotates, giving us a window into Titan’s interior beneath the surface.”

Members of the mission’s science team used Cassini’s Synthetic Aperture Radar to collect imaging data during 19 separate passes over Titan between October 2005 and May 2007. The radar can see through Titan’s dense, methane-rich atmospheric haze, detailing never-before-seen surface features and establishing their locations on the moon’s surface.

Using data from the radar’s early observations, the scientists and radar engineers established the locations of 50 unique landmarks on Titan’s surface. They then searched for these same lakes, canyons and mountains in the reams of data returned by Cassini in its later flybys of Titan.

They found that prominent surface features had shifted [...]

Saturn’s moon Rhea may also have rings

saturns-moon-rhea-may-also-have-rings

Copyright ESA

The Cassini spacecraft has found evidence of material orbiting Rhea, Saturn’s second largest moon. This is the first time rings may have been found around a moon.

A broad debris disc and at least one ring appear to have been detected by a suite of six instruments on Cassini specifically designed to study the atmospheres and particles around Saturn and its moons.

“Until now, only planets were known to have rings, but now Rhea seems to have some family ties to its ringed parent Saturn,” said Geraint Jones, a Cassini scientist and lead author on a paper that appears in today’s issue of the journal Science. Jones began this work while at the Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, and is now at the Mullard Space Science Laboratory, University College London, UK.

Rhea is roughly 1500 km in diameter. The apparent debris disc measures several thousand kilometers from end to end. The particles that make up the disc and any embedded rings probably range from the size of small pebbles to boulders. An additional dust cloud may extend up to 5900 km from the moon’s centre, almost eight times the radius of Rhea.

“Like finding [...]

Saturns moon Iapetus is the Yin-Yang of the Solar System

saturns-moon-iapetus-is-the-yin-yang-of-the-solar-system

Copyright ESA

Cassini scientists are poring through hundreds of images returned from the 10 September fly-by of Saturn’s two-toned moon Iapetus.

The pictures show the moon’s yin and yang – a white hemisphere resembling snow, and the other as black as tar.

Images returned late Tuesday and early Wednesday show a surface that is heavily cratered, along with the mountain ridge that runs along the moon’s equator. Many of the close-up observations focused on studying the strange 20-km high mountain ridge that gives the moon a walnut-shaped appearance.

“The images are really stunning,” said Tilmann Denk, Cassini imaging scientist at the Free University in Berlin, Germany, who was responsible for the imaging observation planning. “Every new picture contained its own charm. I was most pleased about the images showing huge mountains rising over the horizon. I knew about this scenic viewing opportunity for more than seven years, and now the real images have suddenly materialised.”

This fly-by was nearly 100 times closer to Iapetus than Cassini’s 2004 fly-by, bringing the spacecraft to about 1640 km from the surface. The moon’s irregular walnut shape, the mountain ridge that lies almost directly on the equator and Iapetus’ brightness contrast are among the [...]

Two more active moons around Saturn

two-more-active-moons-around-saturn

Copyright ESA

Saturn’s moons Tethys and Dione are flinging great streams of particles into space, according to data from the NASA/ESA/ASI Cassini mission to Saturn. The discovery suggests the possibility of some sort of geological activity, perhaps even volcanic, on these icy worlds.

The particles were traced to the two moons because of the dramatic movement of electrically charged gas in the magnetic environs of Saturn. Known as plasma, the gas is composed of negatively charged electrons and positively charged ions, which are atoms with one or more electrons missing. Because they are charged, the electrons and ions can get trapped inside a magnetic field.

Saturn rotates around itself in just 10 hours and 46 minutes. This sweeps the magnetic field and the trapped plasma through space. Just like a child on a fast-spinning merry-go-round, the trapped gas feels a force trying to throw it outwards, away from the centre of rotation.

Soon after Cassini reached Saturn, in June 2004, it revealed that the planet’s hurried rotation squashes the plasma into a disc and that great fingers of gas are indeed being thrown out into space from the disc’s outer edges. Hotter, more tenuous plasma then rushes in to fill [...]

Predicting the weather on Titan

predicting-the-weather-on-titan

Copyright ESA

Using recent Cassini, Huygens and Earth-based observations, scientists have been able to create a computer model which explains the formation of several types of ethane and methane clouds on Titan.

Clouds have been observed recently on Titan, Saturn’s largest moon, through the thick haze, using near-infrared spectroscopy and images of the south pole and temperate regions near 40° South. Recent observations from Earth-based telescopes and the NASA/ESA/ASI Cassini spacecraft are now providing an insight into cloud climatology.

A European team, led by Pascal Rannou of the Service d’Aeronomie, IPSL Universite de Versailles-St-Quentin, France, has developed a general circulation model which couples dynamics, haze and cloud physics to study Titan climate and enables us to understand how the major cloud features which are observed, are produced.

This climate model also allows scientists to predict the cloud distribution for the complete Titan year (30 terrestrial years), and especially in the next years of Cassini observations.

The Voyager missions of the early 1980s gave the first indications of condensate clouds on Titan. Because of the cold temperatures in the moon’s atmosphere (tropopause), it was assumed that most of the organic chemicals formed in the upper atmosphere by photochemistry would condense into [...]