Roughly 1,000 Kuiper Belt objects have been discovered orbiting beyond Neptune since the first was found in 1992. Now researchers are suggesting that these icy objects -- considered to be leftover building blocks of the solar system -- are much smaller than was originally thought. The key is albedo, a measure of how much light an object reflects. Using a presumed albedo of four percent, which is the figure for comets, astronomers had calculated the size of the Kuiper Belt objects, and believed there were more than 10,000 KBOs with diameters greater than 100 kilometers (62 miles), compared to 200 asteroids known to be that large in the main asteroid belt between Mars and Jupiter. But all these measurements depend on an accurate read on albedo. A higher albedo means a more reflective object, forcing a reassessment of how large the KBO objects really are. Image: Kuiper Belt Object 2002 AW197 (Image: NASA/JPL/John Stansberry, University of Arizona) And as reported at the ongoing meeting...

The news from Titan could not be more curious. Radar imagery shows dark areas that may be smooth plains choked with ice, or perhaps pools of liquid methane. The early photographs showed few topographical features, due largely to the diffuse glare that reduces shadows under Titan's thick atmosphere. But processed radar images showed rough terrain interspersed with darker areas that seem to be flat. Variations in elevation appear to be no more than 150 feet in the area most closely studied, according to this article in the New York Times (free registration required). And what are these strange surface streaks in the equatorial region? Early speculation is that they are ridges of ice or deposits of some kind of windblown material. Image: This medium-resolution view shows some of the surface streaks of Titan's equatorial terrain. The streaks are oriented roughly east to west; however, some streaks curve to the north and others curve to the south, perhaps due to the topography of this...

A Cassini close encounter news briefing will be available on NASA TV at 12 PM EST today. Live interviews on the Titan flyby will appear in segments from 3 to 7 PM EST this afternoon. A science briefing occurs tomorrow at 12 PM EST (all programs subject to change without notice, adds NASA). For more, check both the Cassini-Huygens home page and the Cassini Imaging Team page. Also, a nice interview with Jonathan Lunine, of the Lunar and Planetary Laboratory at the University of Arizona, is here. Back to the usual interstellar rounds soon, but for now, Titan is too fascinating to ignore. This image is one of the closest ever taken of Saturn's hazy moon Titan. It was captured by Cassini's imaging science subsystem on Oct. 26, 2004, as the spacecraft flew by Titan. At its closest, Cassini was 1,200 kilometers (745 miles) above the moon, 300 times closer than during its first flyby on July 3, 2004. Credit: NASA/JPL/Space Science Institute. A few salient facts: Cassini came within 1200...

We'll soon have many more images, but for now, this view of Titan taken on the 24th may give a foretaste of what's to come. Here's the image, along with NASA's description, of the extraordinary feature that recalls Coleridge: In Xanadu did Kubla Khan A stately pleasure-dome decree: Where Alph, the sacred river, ran Through caverns measureless to man Down to a sunless sea. NASA's commentary: "This image taken on Oct. 24, 2004, reveals Titan's bright "continent-sized" terrain known as Xanadu. It was acquired with the narrow angle camera on Cassini's imaging science subsystem through a spectral filter centered at 938 nanometers, a wavelength region at which Titan's surface can be most easily detected. The surface is seen at a higher contrast than in previously released imaging science subsystem images due to a lower phase angle (Sun-Titan-Cassini angle), which minimizes scattering by the haze. "The image shows details about 10 times smaller than those seen from Earth. Surface materials...

The Cassini Saturn orbiter will make its closest approach yet to Titan tomorrow, traveling 1200 kilometers (745 miles) above the surface at a speed of 6.1 kilometers per second. This will be the first time Cassini has used its radar instruments to image the moon. Confirmation that data from the flyby were successfully received won't come in until evening (6:30 PM PDT) on the 26th. A close look at the imaging and radar data will be fascinating in itself, but this flyby is also a crucial part of the attempt to land the Huygens probe on Titan, an event now scheduled for January 14, 2005 (with separation of the lander from Cassini on Christmas day). A prime objective is to determine whether the landing area for the probe is solid or liquid in nature. Image: Encircled in purple stratospheric haze, Titan appears as a softly glowing sphere in this colorized image taken one day after Cassini's first flyby of that moon. Credit: NASA/JPL/Space Science Institute. Says professor Michele...

The European Southern Observatory labeled yesterday the 'Day of Toutatis,' when the 4.6 kilometer-long asteroid passed Earth at no more than four times the Earth-Moon distance. Discovered in 1989, Toutatis swings close to Earth every four years, but not since 1353 has it come as close as yesterday. Closest approach occurred at roughly 1340 hours GMT (0940 ET). ESO's coverage can be found here. Near-Earth asteroids like Toutatis are a reminder of the space debris that has showered Earth throughout its history. Our future in space is not optional: we'll need the technology to detect and deflect any asteroids that seem likely to make impact (Toutatis does not), and that means building up a space-based infrastructure into the outer Solar System. It is exactly that kind of system-wide presence that will one day allow us to build and send our first interstellar probes. You can read more about Toutatis at NASA's Near Earth Object Program site. Image: Asteroid 4179 Toutatis, November 26,...

The European Space Agency has announced that the Huygens probe has passed its second to last in-flight checkout, in preparation for deployment to Titan in December. The critical Mission Timer Unit is in good health, a must given the fact that Huygens will coast for several weeks after being released by the Cassini Saturn orbiter. The MTU will be charged with waking Huygens up just before entry into Titan's atmosphere. ESA's coverage is here.