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Titan starts to reveal its secrets

As Huygens probe has landed on it and Cassini has made a few passes of it, Saturn's largest moon Titan is starting to reveal its secrets.

Titan, long held to be a frozen analog of early Earth, has liquid methane on its cold surface. Among the new discoveries is what may be a long river, roughly 1,500 kilometers long (930 miles). Scientists have also concluded that winds on Titan blow a lot faster than the moon rotates, a fact long predicted but never confirmed until now.

Titan has a surface shaped largely by Earth-like processes of tectonics, erosion, winds, and perhaps volcanism. Tectonism (brittle fracturing and faulting) has clearly played a role in shaping Titan’s surface. Erosion by fluids may accentuate the tectonic fabric by depositing dark materials in low areas and enlarging fractures. This interplay between internal forces and fluid erosion is very Earth-like.

Titan’s winds are measured by watching its clouds move. Clouds are rare on Titan, and those that can be tracked are often too small and faint to be seen from Earth. Ten clouds have been tracked by Cassini, giving wind speeds as high as 34 meters per second (about 75 miles per hour) to the east — hurricane strength — in Titan’s lower atmosphere.

Cassini is scheduled to make 41 additional close Titan flybys in the next three years.

posted by: kyawoo at 10:57 | link | comments |
saturn

Twisted ring of Saturn

Saturn’s F ring shows distinct twists and kinks in this image taken by Cassini spacecraft. The perturbations are caused by the gravitation interaction of Saturn’s F ring shepherd moon Prometheus as it orbits Saturn once every 14.7 hours .

posted by: kyawoo at 22:17 | link | comments (2) |
saturn, unmanned missions

Earth-flyby of comet-chasing spacecraft

Rosetta spacecraft performed closest-ever Earth fly-by on 4 March 2005 as it builds up the speed needed to chase down and orbit a comet in 2014. Rosetta passed above the Pacific Ocean just west of Mexico at an altitude of 1954.74 km and a velocity relative to the Earth of 38 000 kph. It is the first of three Earth flybys Rosetta will make before travelling through the asteroid belt to Jupiter. There, it will rendezvous with the Comet 67P/Churyumov-Gerasimenko. The fly-bys, known as "Gravity Assist", are necessary to accelerate the spacecraft so as to eventually match the velocity of the target comet. They are a fuel-saving way to boost speed using planetary gravity.

The fly-by manoeuvre swung the three-tonne spacecraft around our planet and out towards Mars, where it will make a fly-by on 26 February 2007. Rosetta will return to Earth again in a series of four planet fly-bys (three times with Earth, once with Mars) before reaching Comet 67P/Churyumov-Gerasimenko in 2014.

Once in orbit around the comet, the craft will despatch a small lander called Philae to the surface to study its chemistry.

Rosetta is the first mission designed to both orbit and land on a comet, and consists of an orbiter and a lander. The spacecraft carries 11 scientific experiments and will be the first mission to undertake long-term exploration of a comet at close quarters. After entering orbit around Comet 67P/Churyumov-Gerasimenko in 2014, the spacecraft will release a small lander onto the icy nucleus. Rosetta will orbit the comet for about a year as it heads towards the Sun, remaining in orbit for another half-year past perihelion (closest approach to the Sun).

Comets are believed to contain materials that have remained largely unchanged since the formation of the Solar System 4.6bn years ago, and Rosetta data should help researchers understand better how our local space environment has evolved over that time.

posted by: kyawoo at 05:11 | link | comments |
unmanned missions, comets

Saturn's Rings Evaporating

Saturn's rings are evaporating into a puff of oxygen, according to researchers who have found evidence of molecular oxygen in Saturn's tightest ring. The first measurements of molecular oxygen were made by Cassini spacecraft, as it recently passed within 7,000 kilometers (4,350 miles) of the A-ring — the ring closest to Saturn. It's also the first direct evidence that life, in the form of photosynthetic plants, isn't required to create molecular oxygen. The discovery backs the idea that the solar radiation and micro-meteor impacts are gradually breaking down the rings. What appears to be going on is that solar radiation is splitting the water molecules (H2O) in the ring ice particles. The lightweight hydrogen freed by the radiation probably floats away and then falls into Saturn's hydrogen-rich atmosphere, leaving a thin veneer of heavier molecular oxygen gas, which is slower to dissipate, bathing the ring. Calculations of the rate of dissipation put the life of rings at tens of millions of years, far less than the billions of years that the planet has existed. The discovery could also fuel a theory about Jupiter's icy moon Europa. It's thought that Europa could harbor life in a liquid water sea under a thick layer of ice, but the problem is there's no obvious source of oxygen. Evidence collected by the Galileo spacecraft indicates that the harsh radiation around Jupiter is making O2 on Europa in a similar way to how O2 is being made in the rings of Saturn. That O2 could make it under the ice via cracks and daily tidal surge of water inside the ice.

posted by: kyawoo at 20:54 | link | comments (1) |
saturn

Voyager-1 becomes the furthest human-made object from the Sun

The intrepid twin Voyager spacecraft, launched about two weeks apart in the summer of 1977 and now heading out of the solar system. The primary mission was the exploration of Jupiter and Saturn. After making a string of discoveries there -- such as active volcanoes on Jupiter's moon Io and intricacies of Saturn's rings -- the mission was extended. Voyager 2 went on to explore Uranus and Neptune, and is still the only spacecraft to have visited those outer planets. The adventurers' current mission, the Voyager Interstellar Mission (VIM), will explore the outermost edge of the Sun's domain. And beyond. During the journey, the Voyagers returned nearly 80 thousand images and more than 5 trillion bits of data. After traveling through space for more than 27 years, Voyager 1 is now heading in a northerly direction toward interstellar space. Voyager 2 is headed on a southerly path toward interstellar space. Voyager 1 is now the furthest human-made object from the Sun, having surpassed Pioneer 10 on February 17, 1998. Both spacecraft are still going strong and are returning valuable science data. Both spacecraft are expected to continue to operate and send back valuable data until at least the year 2020.

posted by: kyawoo at 22:10 | link | comments (2) |
unmanned missions

Solar storm depleted ozone layer

The gigantic solar storms of November 2003 severely depleted the ozone layer above the Arctic for as long as eight months, suggest newly released satellite observations. The planet's magnetic field funnelled some of the storm's electrons into the upper atmosphere above the poles. The electrons hit nitrogen molecules there, breaking some of them into nitrogen ions. Those reactive atoms then combined with nearby oxygen molecules to form molecules of nitrogen oxide - levels of which rose in November and December 2003, according to the satellite data. Finally, downward-blowing winds in a polar vortex above the Arctic pushed these molecules into the stratosphere. There, each nitrogen oxide molecule could rip apart hundreds of ozone molecules, just as CFCs do. The effect remained even into July 2004. But ozone was not affected in the upper stratosphere over the Antarctic because of a seasonal effect.

posted by: kyawoo at 09:49 | link | comments (3) |
sun, earth

Blue sky on Saturn

Saturn is supposed to be yellow. Sunlight reflected from those clouds is what gives Saturn its golden hue But NASA’s Cassini spacecraft discovered sunny blue skies on Saturn in 2005. While Saturn’s northern hemisphere has blue skies, Saturn’s southern hemisphere does not. The south looks yellow. It could be that southern skies on Saturn are simply cloudier, yellow clouds making yellow skies. Saturn’s north is so blue that amateur astronomers could see the hue from Earth. Unfortunately, the north of Saturn is hidden at the moment behind Saturn’s rings, a situation that will persist for another year or so. For now, Cassini is in the best position to investigate. Will Saturn’s blue skies fade? Or grow to envelop the whole planet? We must wait and see.

posted by: kyawoo at 11:25 | link | comments |
saturn