Of the many things demonstrated by the Deep Impact mission to comet Tempel 1, the evolution of astronomy is not the least significant. Gone are the days of the isolated mountain-top observer painstakingly examining photographic plates whose findings might be corroborated only weeks or months later by other astronomers. During the Deep Impact mission, the European Southern Observatory used every modern communications tool in the book as part of a collaboration between all major observatories worldwide. The result: round the clock data through a wide variety of instruments both Earth and space-based, making Deep Impact a hugely successful example of distributed astronomy -- 'distributed' as in 'distributed computing,' where powerful resources share their capabilities to produce a result far greater than any one of them could achieve. From all this, we know that Tempel 1 was not significantly transformed by the Deep Impact collision. In fact, the impactor evidently did not create a...

Each new world we visit offers a different perspective on how planets and their moons form. Consider Saturn's moon Hyperion, the density of which now appears to be only about 60 percent that of solid water ice. What that means is that much of the moon's interior -- 40 percent or more -- is made up of empty space, so that Hyperion is not so much a solid body as a conglomeration of icy rubble. The Hubble images acquired between June 9 and 11 confirm this estimate, showing an object that looks almost sponge-like, bearing the imprint of countless craters which seem relatively recent. What we can gather from all this is that Hyperion is a moon that is pushing a critical limit beyond which the internal pressure of its gravity would start to crush weaker materials, closing up those porous spaces and establishing the more familiar spherical shape of larger bodies. Hyperion's diameter (adjusting for its irregular shape) is 360 x 280 x 225 km (223 x 174 x 140 miles). We'll have a much closer...

Tempel 1, the comet that slammed into the Deep Impact probe on July 4, is three miles wide by seven miles long, and evidently coated with a fine, powdery dust. That dust, says Deep Impact principal investigator Dr. Michael A'Hearn of the University of Maryland, is more like talcum powder than beach sand. "The major surprise was the opacity of the plume the impactor created and the light it gave off," said A'Hearn, adding "And the surface is definitely not what most people think of when they think of comets -- an ice cube." Meanwhile, the immense data recovery and analysis process continues. 4500 images were taken by the spacecraft's three cameras, with the memory of the impactor's plunge into the comet's nucleus still fresh. The final images from the impactor showed surface detail down to the level of four-meter objects, a factor of ten better than any previous comet mission. And we now know that the impactor hit the nucleus at a 25 degree oblique angle relative to the cometary...

Scientists now believe that Deep Impact's 820-pound impactor vaporized deep inside comet Tempel 1's surface when the collision took place on July 4. Moving at 23,000 miles per hour, the impact would have been severe, generating temperatures of several thousand degrees Kelvin, and creating what Dr. Pete Schultz of Brown University calls "...our own incandescent photo flash." Even 50 minutes after Tempel 1 and the impactor collided, the visual effects were still striking, as shown in this spectacular photo from the flyby probe. In the second photograph, taken from the impactor probe, the comet is seen in startling detail. Note the topographical features, which include what may be ancient impact craters and a variety of ridge lines. Clearly, Deep Impact wasn't the first object to hit this comet! Image credit for both photos: NASA/JPL-Caltech/UMD. Meanwhile, x-rays from Tempel 1 have been confirmed by the XMM-Newton space observatory. Previous observations of comets had suggested that...

The Hubble images below (click to enlarge) give an idea of the size of the Deep Impact event. At left is the comet Tempel 1 before the collision. In the middle image, taken 15 minutes after impact, the comet is four times brighter than before and shows a substantially increased cloud of dust and gas. The image at far right was taken over an hour after the collision. Note the fan shape of the ejecta -- the debris, according to this Hubble news release, is pushing outward at about 1800 kilometers per hour. Image: The potato-shaped comet is 14 kilometres wide and 4 kilometres long. Tempel 1's nucleus is too small even for the Hubble telescope to resolve. These visible-light images were taken by the Advanced Camera for Surveys' High Resolution Camera. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA). Data from Deep Impact continue to accumulate. Images taken by ESA's XMM-Newton observatory (an x-ray observatory based in space) show the emissions of hydroxyl ions, the direct...

Deep Impact gave mission scientists what they bargained for -- and more-- when its impactor collided with comet Tempel 1 last night. The collision occurred at 0152 EDT (0652 GMT), with the first image returning at 0157. Calling the impact 'spectacular,' principal investigator Dr. Michael A'Hearn of the University of Maryland, College Park added, ""With this much data we have a long night ahead of us, but that is what we were hoping for. There is so much here it is difficult to know where to begin." Note the use of autonomous navigation aboard the impactor, which was released from the mothership at 0207 EDT (0607 GMT) on the 3rd. On its own, the impactor needed to make three targeting maneuvers as it closed on the comet, the first of these 90 minutes before impact, followed by two more at 35 and 12.5 minutes respectively. The result: a 10 kilometer per second collision with the comet, while the mothership monitored events from nearby, and legions of telescopes followed the action from...

Deep Impact successfully released its 820-pound impactor this morning at 2:07 EDT (0607 GMT), some 880,000 kilometers from the Tempel 1 comet. The Jet Propulsion Laboratory has also reported that six hours before release of the impactor, the spacecraft performed a successful trajectory correction, using a 30-second burn to change Deep Impact's velocity by about one kilometer per hour. Another burn occurred twelve minutes after impactor release, when the flyby spacecraft began a 14-minute burn designed to move it out of the path of the oncoming comet and place it in the best position to observe the impact. Image: One hundred and seventy-one days into its 172-day journey to comet Tempel 1, NASA's Deep Impact spacecraft successfully released its impactor at 2:07 a.m. Sunday, Eastern Daylight Time. This image of Deep Impact's impactor probe was taken by the mission's mother ship, or flyby spacecraft, after the two separated. Image credit: NASA/JPL-Caltech.

No one knows quite what to expect when the Deep Impact probe slams into comet Tempel 1, but countless amateur astronomers plan to be watching to see if the comet brightens following the collision. And it might, given the amount of material that could be dislodged by the event. A telescope or set of binoculars will probably be required, although dedicated skywatchers can still see the spot in the sky where the big event will occur even without the aid of such equipment. The time of impact is 1:52 EDT (0552 GMT) on the morning of July 4, a time when the comet will be best placed for viewing from the American southwest, although Kelly Beatty, executive editor of SKY & TELESCOPE magazine, is now saying that anyone west of the Mississippi has a good chance of seeing it. From a news release just issued by the magazine, here is where to look: After dark, find Jupiter shining high in the southwest. It's the brightest "star" in that part of the sky (brighter Venus sets in the west-northwest...

All the observing time on comet Tempel 1 as the Deep Impact spacecraft approaches is really paying off. Scrutinized by ground and space-based telescopes, the comet was seen to emit a small outburst of materials on June 14. Now Deep Impact has seen a much more massive ejection of ice and other particles that occurred on June 22. Although six times larger than the earlier one, the new outburst dissipated quickly, within about half a day. Intriguingly, the spectrometer aboard Deep Impact showed that the amount of water vapor in the coma doubled during this event, while the amount of other gases, including carbon dioxide, increased even more. From a University of Maryland news release, quoting Michael A'Hearn, who leads the Deep Impact mission: "Outbursts such as this may be a very common phenomenon on many comets, but they are rarely observed in sufficient detail to understand them because it is normally so difficult to obtain enough time on telescopes to discover such phenomena," said...

Here's the Deep Impact target, as seen by the Hubble Space Telescope in a dramatic set of images that show a jet of dust blowing away from the comet's nucleus. At the time the photos were taken -- seven hours apart on June 14 -- Hubble was 120 million kilometers away; the images come from the space observatory's Advanced Camera for Surveys' High Resolution Camera. Tempel 1, it is hoped, will provide an even more spectacular show when Deep Impact reaches it on July 4, releasing an 820 lb. copper impactor that will slam into the comet. The image on the left shows the comet before the new jet formed. In the center of the image, the bright dot is the reflection of light off the comet's nucleus, which is too small at these distances for Hubble to resolve. The nucleus is thought to be about 14 kilometers wide and 4 kilometers long, about as hard to see, according to an ESA press release, "...as someone trying to spot a potato in Stockholm from Madrid." At the right, a bright area in the...

What can you do with a vertical gun range? NASA's Ames Research Center has one, a three story tall machine that fires objects into the surface of your choice. Of late, Brown University professor of geology Peter Schultz has been using it to fire marble-sized beads into surfaces ranging from dust to ice and snow. Moving faster than a speeding bullet -- ten times as fast -- the objects create craters, and craters are something Schultz has made a career studying. As you might imagine, this expertise has caught NASA's eye, and the agency hopes to use Schultz' work to analyze the results of the fireworks set to go off on July 4, when comet Tempel 1 runs headlong into the Deep Impact probe. The professor is one of 13 co-investigators overseeing the mission, which is designed to study what comes out of the comet when the spacecraft's 820-pound copper impactor separates from the mothership and becomes a cometary target. From a Brown University news release: "This is heady stuff," Schultz...