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 [...]

Ocean may exist beneath Titan's 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 [...]

Building our new view of Titan


Copyright ESA

On 14 January 2005, after a seven-year voyage on board the NASA/ESA/ASI Cassini spacecraft, ESA’s Huygens probe spent 2 hours and 28 minutes descending by parachute to land on Titan. It then sent transmissions from the surface for another seventy minutes before Cassini moved out of range.

On 8 December that year, a combined force of scientists published their preliminary findings in Nature. Now, after another year and a half of patient work, they are ready to add fresh details to their picture of Titan. This time, the papers are published in a special issue of the Planetary and Space Science magazine.

“The added value comes from computer modelling,” says Jonathan Lunine, Huygens Interdisciplinary Scientist from the Lunar and Planetary Laboratory, University of Arizona.

By driving their computer models of Titan to match the data returned from the probe, planetary scientists can now visualise Titan as a working world. “Even though we have only four hours of data, it is so rich that after two years of work we have yet to retrieve all the information it contains,” says François Raulin, Huygens Interdisciplinary Scientist, at the Laboratoire de Physique et Chimie de l’Environnement, Paris.

The new details add [...]

The jet stream of Titan


Copyright ESA

A pair of rare celestial alignments that occurred in November 2003 helped an international team of astronomers investigate the far-off world of Titan. In particular, the alignments helped validate the atmospheric model used to design the entry trajectory for ESA’s Huygens probe.

Now the unique results are helping to place the descent of Huygens in a global context, and to investigate the upper layers of Titan’s atmosphere.

Occasionally Titan passes directly in front of a distant star. When it does so, the light from the star is blocked out. Because Titan has a thick atmosphere, the light does not ‘turn off’ straight away. Instead, it drops gradually as the blankets of atmosphere slide in front of the star. The way the light drops tells astronomers about the atmosphere of Titan.

By pure chance on 14 November 2003, fourteen months before Huygens’ historic descent through Titan’s atmosphere, Titan passed in front of two stars, just seven and a half hours apart. Bruno Sicardy, Observatoire de Paris, France, organised expeditions to record the occultations, as such events are called.

The first occultation was visible just after midnight from the Indian Ocean and the southern half of Africa. The second could [...]

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 [...]

Europe reaches new frontier -Huygens lands on Titan


Copyright ESA

ESA PR 03-2005. Today, after its seven-year journey through the Solar System on board the Cassini spacecraft, ESA’s Huygens probe has successfully descended through the atmosphere of Titan, Saturn’s largest moon, and safely landed on its surface.

The first scientific data arrived at the European Space Operations Centre (ESOC) in Darmstadt, Germany, this afternoon at 17:19 CET. Huygens is mankind’s first successful attempt to land a probe on another world in the outer Solar System. “This is a great achievement for Europe and its US partners in this ambitious international endeavour to explore the Saturnian system,” said Jean-Jacques Dordain, ESA’s Director General.

Following its release from the Cassini mothership on 25 December, Huygens reached Titan’s outer atmosphere after 20 days and a 4 million km cruise. The probe started its descent through Titan’s hazy cloud layers from an altitude of about 1270 km at 11:13 CET. During the following three minutes Huygens had to decelerate from 18 000 to 1400 km per hour.

A sequence of parachutes then slowed it down to less than 300 km per hour. At a height of about 160 km the probe’s scientific instruments were exposed to Titan’s atmosphere. At about 120 km, [...]

Splashing down on Titan's oceans


Copyright ESA

Titan, Saturn’s largest moon, is a mysterious place. Its thick atmosphere is rich in organic compounds. Some of them would be signs of life if they were on our planet. How do they form on Titan? Will they help us to discover how life began on Earth?

ESA’s Huygens probe, arriving at Titan in 2005, will help find answers. Here on Earth, ground-based telescopes are playing their part also. They will help scientists to decide how and where precisely Huygens will land. What will it be – on solid ground or in an ocean of methane?

NASA’s Voyager 1 provided the first detailed images of Titan in 1980. They showed only an opaque, orange atmosphere, apparently homogeneous. It was so thick that you could not see the surface. However, other data revealed exciting things. Similarly to Earth, Titan’s atmosphere is mostly nitrogen but there is also methane and many other organic compounds.

Organic compounds form when sunlight destroys the methane. If sunlight is continuously destroying methane, how is methane getting into the atmosphere? On Earth today, it is life itself that refreshes the methane supply. Methane is a by-product of the metabolism of many organisms. Could this mean [...]