September 24, 2001
Fly-By Images Will Remake Comet Science, Help 'Deep Impact' Mission
By Robert Roy Britt
Senior Science Writer
posted: 11:52 am ET
24 September 2001
Images of a comet taken by the Deep Space 1 spacecraft, along with other data NASA will release Tuesday, will remake what scientists know about the Sun-orbiting ice balls and help planners for an upcoming comet-smashing mission.
The future mission, Deep Impact, will attempt to ram a probe into a comet at high speed, and the manager of that mission now has greater confidence that his team can actually hit the target as planned.
Some 30 black-and-white pictures of comet Borrelly's nucleus were produced when Deep Space 1 flew past the comet Saturday in a maneuver that mission managers did not expect to succeed. The beleaguered but determined craft also made infrared images and recorded data of magnetic fields and other emissions from the comet.
"The images and other data we collected from comet Borrelly are going to make great contributions to scientists' efforts to learn more about these intriguing members of the solar system family," said mission manager Marc Rayman.
The new images and other data will come close to remaking what is known about comets for years to come, Rayman said.
"I think we're going to gain a lot of completely new and absolutely fascinating insights into comets and perhaps into the origin and evolution of Earth," he said.
NASA has set a news conference to reveal the fly-by results for Tuesday, Sept. 25, at 1 p.m. ET.
The black-and-white photographs snapped on Saturday were well centered in the camera's viewfinder and sharp, said Donald Yeomans, a Jet Propulsion Laboratory (JPL) comet and asteroid researcher who was in the control room when early versions of the images first arrived.
Other researchers, who wished not to be quoted because NASA is keeping a tight lid on the fly-by data, agreed that the images and data would be extremely important to the study of comets, about which little is known.
Astronomers have so little data on comets, especially on their internal composition, that there is a wide range of possibilities regarding what they are made of. Among the most well studied comets is 1999 S4 LINEAR, which broke apart during the summer of 2000 in view of several space- and Earth-based telescopes.
Comet LINEAR was found to contain far less water than researchers expected, a result which, if supported by similar findings, could alter scientists' view of the role comets played in supplying Earth's water and making the planet habitable.
But with little to compare it to, scientists could not say whether LINEAR is typical or a special case. Now, with detailed data on two comets, it's possible that scientists will be able to draw broader conclusions.
Next up: Crash into a comet
A handful of other firmly planned missions from both NASA and the European Space Agency will explore comets in greater detail in the next four years. One of the greatest challenges in studying comets from space is that mission planners don't know much about their target, hence they are challenged to program the spacecraft to know what it should be looking for.
This can affect everything from whether the spacecraft actually finds its target to how successfully it pulls off its imaging tasks and other aspects of the mission.
The success of Deep Space 1 has significantly boosted confidence in NASA's Deep Impact mission, which will slam a small probe into comet Tempel 1 on Independence Day 2005 so that researchers can study the material ejected from the comet's nucleus. If it succeeds, Deep Impact will likely provide the true look at the pristine, billions-year-old material inside a comet.
That material is thought to hold secrets of the solar systems formation.
"The images from Deep Space 1 will play a crucial role in refining our predictions of the targeting environment for Deep Impact," said Michael A'Hearn, a University of Maryland astronomer who will manage Deep Impact.
A'Hearn, who was at JPL for Saturday's flyby, said via Email that the accomplishment gives Deep Impact some momentum and provides a measure of confidence for the mission, which is due to launch in January 2004.
"My preliminary look at the data from Deep Space 1 suggests that our predictions for Borrelly were not far off and that, therefore, we can rely on our nominal predictions for Tempel 1, rather than our worst case models, and that we should not have a problem hitting the nucleus," he said.
Deep Space 1 managed to wiggle its way inside the coma of comet Borrelly, a shroud of gas and dust that NASA had feared might have destroyed the craft before it got a chance to take pictures. The probe was not designed for such a flyby and, because it was travelling at 36,900 mph (16.5 kilometers per second), it was defenseless against the powerful impact of even a small bit of dust.
"The fact that DS1 survived the encounter despite having no shielding against the dust in the coma gives us confidence that our flyby, which is shielded against dust, also will not be destroyed by the dust in the coma," A'Hearn said.