Most auroras in the solar system, including Earth's, are caused by the interaction between charged particles in the solar wind and a planet's magnetic field. Saturn has a main aurora that is caused by the solar wind. Jupiter has an aurora caused by the interaction of Jupiter's magnetic field and the magnetic properties of its moons. The infrared aurora on Saturn doesn't fit either of those models. University College London astronomer Nick Achilleos, a member of the Cassini team, said, "Trying to explain its origin will no doubt lead us to physics which uniquely operates in the environment of Saturn."

Scientists will keep an eye on the phenomena in an effort to find more clues about its nature. So far, the aurora has been observed to be highly variable, shifting in size and even periodically disappearing. Image by: NASA/JPL/University of Arizona.

Cassini Finds Mysterious New Aurora On Saturn. [Science Daily]

No one yet has a photo of the fireball that occurred as the asteroid (dubbed 2008 TC3) broke up in the atmosphere, and meteorite fragments will be difficult to find — the impact spot is in northern Sudan near Darfur. But Russian stargazers S. Korotkiy and T. Kryachko, of the Kazan State University Astrotel Observatory, released an animated picture of 2008 TC3's path toward Earth:

Nature reports that NASA was able to give out early warnings of the impact:

On Monday, once Yeomans' office had confirmed the incoming asteroid, he called NASA headquarters in Washington DC, which publicized the impact about seven hours before it occurred. If, however, the incoming object had been 50 to 100 times bigger than it was, the warnings would have been very different. "We would have found out several days sooner," Yeomans says, and arrangements would have been made to get people out of the area of impact.

Alerted of 2008 TC3's proximity and the possibility of seeing a fireball, a Dutch pilot with KLM reported seeing a quick flash in the sky from 1400 kilometers away. An astronomer from Western Ontario even managed to estimate the size of 2008 TC3:

... astronomer Peter Brown of the University of Western Ontario in London, Canada, was able to confirm that the space rock hit the atmosphere at around 02:45 GMT on Tuesday, within minutes of the predicted time and at the predicted location. Brown used data from a Kenya-based array of seven microbarometers, which record atmospheric sound waves to monitor countries' compliance with the Comprehensive Nuclear Test Ban Treaty. The infrasound signals show that the asteroid hit the atmosphere with an energy equivalent to detonating one to two kilotonnes of TNT.

"We can infer from that energy that 2008 TC3 was about three metres in diameter," Brown says.

Though 2008 TC3 was never listed as a potentially hazardous asteroid, its pre-impact discovery and analysis is still an encouraging development for NASA/JPL. Before 2008 TC3 ever entered Earth's atmosphere, astronomers were tracking its progress, and as far as they can tell it burned up just where they said it would. If we can predict the impact of objects this small, it bodes well for our ability to mitigate the imagined disaster scenarios of major impacts.

Great balls of fire [Nature News]
News and information about asteroid impact [Spaceweather.com]

Image from NASA/JPL.

Scientists began to suspect a global ocean when they saw some landmarks on Titan had shifted up to 19 miles between October 2004 and May 2007. The best explanation is a vast ocean, separating the planet's icy crust from its rocky center. The Cassini Space probe will fly within 620 miles of Titan, sample the atmosphere, and take pictures of the site where the Huygens probe landed.

The water has none of the sodium which it would have after years of contact with rock, claims University of Colorado scientist Nick Schneider. But other scientists argue there might be sodium which Schneider's telescope analysis failed to detect. And even Schneider isn't claiming there's no ocean on Enceladus, just that the water jets don't come from it. NASA may have to mount a mission to find out for sure if the Saturn moon holds life forms. Image by NASA/JPL [BBC]