With NASA's EPOXI mission closing on comet Hartley 2 at 12.5 kilometers per second, be aware that live coverage of the close encounter will begin at 1330 UTC (0930 EDT) on Nov. 4 from mission control at the Jet Propulsion Laboratory. NASA TV streaming video will be available, and you should also be able to watch the action on a JPL Ustream channel. Finally, NASA's Eyes on the Solar System Web tool, a 3-D environment for Solar System exploration, is available for viewing a real-time animation of the cometary flyby on your PC. EPOXI is a great instance of re-purposing a spacecraft to extract maximum value. This is the Deep Impact vehicle that gave us such a spectacular view of the impactor smash-up on comet Tempel 1 back in the summer of 2005. Under the name EPOXI, the mission has pressed ahead with two separate objectives, the first being EPOCh, or Extrasolar Planet Observation and Characterization, which has involved a number of nearby stars known to have transiting exoplanets. The...

It's staggering how much our view of the Solar System has changed over the past few decades. The system I grew up with seemed a stable place. The planets were in well-defined orbits out to Pluto and, even if it were always possible another might be found, it surely couldn't pose any great surprise in that great emptiness that was the outer system. But today we routinely track trans-Neptunian objects with diameters over 500 kilometers -- about 50 of these have now been found, and some 122 TNOs at least 300 kilometers in diameter. We know about well over a thousand objects in that ring of early system debris called the Kuiper Belt. It's an increasingly messy place, this outer Solar System, and it has its own terminology. We have centaurs and plutinos, resonance objects, cubewanos, scattered disk objects (SDOs), Neptune trojans, damocloids, apollos and, perhaps, inner Oort cloud objects. Nope, this isn't the Solar System I grew up with, and every new discovery adds to the enchantment....

Here's an interesting bit of news from the New Horizons team. Remember that the spacecraft, having made its pass by the Pluto/Charon system in 2015, will be moving ever deeper into the Kuiper Belt. It's been the hope of mission planners that a close study of one or more objects there might be possible. Now astronomer Scott Sheppard (Carnegie Institution of Washington) has announced that he has detected the first asteroid in Neptune's trailing Trojan zone (the planet's L5 point), an area New Horizons will fly through before arriving at the Pluto/Charon binary. 2008 LC18 is not itself in range for a New Horizons flyby, but mission principal investigator Alan Stern notes its significance in a recent report on the mission's Web site: " ...its discovery shows that additional and potentially closer Neptune Trojans that New Horizons might be able to study could be discovered in the next three years." And that gives us an interesting mission extension for New Horizons, to take advantage of...

Voyager's controllers thought so much of Titan that when Voyager 1 approached Saturn and the choice arose between sending it on to the outer planets or taking a sharp jog off the ecliptic to view the enigmatic moon, they chose the latter. We all know the result: Titan remained as mysterious as ever, its surface shrouded in orange haze. But you can see why they needed that look. Here was a moon that was large enough to be a planet, with a thick atmosphere and all kinds of speculation about what was on its surface. No wonder Titan was the most tempting of targets, and one of huge scientific value. These days we routinely get Cassini imagery from Titan flybys, and the place has gained definition. I remember once asking Geoffrey Landis, having read his superb 2000 novel Crossing Mars, whether Mars had become more or less an everyday place to him, like Cleveland (he lives there, working at NASA GRC). And it was true: After you study and survey and write novels about a place, it does...

The outer Solar System has always been something of an obsession for me, to the point where as a kid, I used to haunt the libraries looking for books on planetary science. Absurdly, I had the notion that even though little was known about places like Triton and Pluto, I might just stumble upon the one book that had details known to no one else. So I would work my way through the shelf, finding the odd speculation here, the small insight there, but it wouldn't be until Voyager's 1989 Neptune flyby that some of these places began to take on actual shape for all of us. All the Myriad Ways And then there was Larry Niven's 'Wait It Out,' a short story from the Known Space universe that was originally published in 1968, in a wonderful collection called All the Myriad Ways. Here a team of astronauts on the surface of Pluto is marooned and the narrator, after his comrade has died, removes his helmet, freezing to death so quickly that his brain becomes a superconductor, so that a strange form...