NASA Waits For The Dust To Settle

As dust and debris shot out of a comet by a NASA space probe, earthbound scientists gathered reams of data that will be analyzed over the coming weeks in search of answers to questions about Earth's earliest days.

Jim Lyke, support astronomer at W.M. Keck Observatory in Waimea, said a day later dust and gas was still spewing from the impact site of the comet. The Big Island observatory planned to view the comet again Monday night.

Before the collision, the Deep Impact science team started an informal betting pool to guess the size of that crater, reports CBS News Space Consultant Bill Harwood. Pre-impact estimates ranged from a crater the size of a house to one the size of a football stadium.

Ignoring the effects of the atmosphere, the impactor would have blasted a 100-foot-wide crater had it hit a solid surface on Earth, releasing the energy of 4.5 tons of TNT. The energy release when it hit Tempel 1 was roughly the same, scientists believe, but the crater almost certainly was much bigger.

"The difference is the gravity is so low it's like the Energizer bunny, it doesn't stop, it just keeps on flowing out," Pete Schultz, a cratering expert at Brown University and a member of the Deep Impact team, told CBS News. "Density and the low gravity, both of those things would make this thing much bigger."

Cadres of astronomers have only just begun to sift through the data from the collision, furiously sending e-mails to colleagues across the globe with their latest observations.

"My inbox has just been full of reports from around the world," Jim Lyke, support astronomer at W.M. Keck Observatory in Waimea, Hawaii, said.

One of the biggest questions to be answered is whether Earth's water came from millions of comets crashing into the planet and its atmosphere, he said.

Sunday's collision may provide evidence that the same isotopes of hydrogen found in Earth's water are also present on the comet, he said.

"If they're different, that's also very important because it says ... if the water was delivered by comets it was changed somehow, or there has to be some other source of this water," he said.

However, it is still too soon to tell whether or not the data will be clear enough to yield that answer, he said.

Scientists will likely be sharing some preliminary conclusions over the next several weeks, but more developed observations won't likely be published until a month from now, he said.

Scientists hope that by blasting into the core of the rocky, ice-filled comet they will learn more about the origins of the sun and planets. A giant cloud of gas and dust collapsed to create Earth's solar system about 4.5 billion years ago, and comets formed from the leftover building blocks of the solar system.
More than 10,000 people watched live images from NASA broadcast onto a movie screen at the beach at Waikiki. Several thousand more watched at other points throughout the islands including the W.M. Keck Observatory.

The timing for the collision was selected for optimal viewing by the powerful telescopes atop Mauna Kea on the Big Island and Haleakala on Maui.

The ejecta cloud extends "thousands of kilometers at least," principal investigator Michael A'Hearn said. "Whether they go further requires more image processing to know. It is certainly largely dust. We see mostly dust in those images because that's what's reflecting the sunlight and by then, that early flash has cooled off. On the other hand there is probably water vaporizing from ice that is driving some of that. So there is gas with it, but that's not what you actually see in the image."

A'Hearn said the debris was "still coming out for at least several hours after the impact event.

"This will be important for understanding the nature of the material at the bottom of the crater," he said. "If there's a lot of volatiles there, the outgassing will continue to go on for a long time. It could go on for weeks. So that spectacular image is really important to the science."

The Deep Impact photos also provide the best views yet of a comet's nucleus. Prior to the collision, Tempel 1 was thought to be pickle shaped, but the reality proved much different.

"It obviously does not look like a pickle or a cucumber or the various things we've talked about before. It looks closer to a loaf of bread or a muffin or something like that," A'Hearn joked.

"There is a lot of topographic relief. There are things on this nucleus that really do look like impact craters to many of us. It looks very different from either comet Wild 2 or comet Borelli, the two comets we've had closeup imaging of in recent years. We don't understand what this means yet.

"When Wild 2 looked different from comet Borelli, we thought it might be due to the different orbital histories of the two comets," A'Hearn said. "But this comet's had an orbital history that we think its pretty much similar to comet Borelli and yet it looks totally different. So there's something more going on here that we haven't understood yet."