Cambridge, England (AFP) Sep 06, 2005
The first detailed analysis from a US mission that smashed a hole in a comet suggests these wanderers are fragile agglomerations of dust, laced with carbon molecules that some theorists say sowed the seeds for life on Earth.
Scientists who staged the Deep Impact mission, which climaxed on July 14 when a projectile the size of a washing machine wacked into Comet Tempel 1, said Tuesday that the data stirred both quiet satisfaction and amazement.
They said some long-standing hypotheses about comets have been given the comfort of evidence -- but others have been swept away.
Chemical analysis from the plume of dust and gas that spewed from the impact showed largely predicted volumes of silicates, including organic (carbon-based) molecules.
Chief scientist Michael A'Hearne, presenting the research on the sidelines of a meeting of US and European astronomers, said this discovery buttressed a contested theory about the origins of life on Earth.
Under the "pan-spermia" idea, comets pounded the early Earth billions of years ago, bringing the planet organic molecules that reacted with light and heat from the sun, eventually providing the rich chemical soup from which all life began.
The pan-spermia theory, initially opposed as outlandish by some scientists, is steadily winning converts, although it remains reviled by fundamentalist Christians as an assault on creationism.
"I would argue that it (the pan-spermia theory) is (now) more likely, just because we have seen this big enhancement in organic materials coming out," A'Hearne told a teleconference.
Early analysis suggested comets were rich in carbon dioxide, acetylene, ammonium and hydrogen cyanide, and a wider range of carbon molecules was likely to be found as scrutiny of the data progressed, he said.
On the other hand, a mainstream view that comets are assemblies of rubble and ice seems destined to become a footnote of cosmic history.
Spectrometers, cameras and other instruments, wielded by a waiting spacecraft and by Earth-based astronomers as the metal missile struck Tempel 1, showed the comet has a fragile crust, underneath which lies a porous structure comprising roughly two parts microscopic dust to one part ice.
No evidence was found of any larger pieces or a cometary "core".
Until now, comets have been dubbed "dirty snowballs", but A'Hearne said it might be appropriate to call them "snowy dirtballs" given the extraordinary dominance of ultrafine dust.
"It's like a brittle sponge... which crumbles in your hand," said Uwe Keller, a scientist with the European Space Agency's comet-chasing probe Rosetta, which turned its own eyes on the collision on July 14 to add to the data flow.
Keller said the extraordinarily fragile surface of Tempel 1 could pose problems for the Rosetta team, which would have to calculate whether a proposed landing on Comet Churyumov-Gerasimenko in 2014 might end disastrously.
If the comet's crust could not withstand the impact from a fridge-sized robot lab, which was due to land and fire an anchor into the surface, the spacecraft would sink through the surface, he said.
Deep Impact's projectile gouged a crater about 100 metres (yards) across "and tens of metres" deep, said A'Hearne. Water molecules were a significant component of the plume, accounting for roughly 5,000 tonnes of it.
Millions of comets encircle the sun and as they near the star, the solar heat melts the ice, leaving a trail of dust that is illuminated as a long tail. Comets have always been linked in superstitious minds with great events, good and bad.
They are equally beguiling for astrophysicists, who believe they are the most primitive material from the early days of the solar system.
Comets are considered to be the leftovers from the massive cloud of gas and dust that condensed and then coagulated to form the sun, the planets and other parts of the solar system about 4.6 billion years ago.
Scientists say understanding the substance and structure of comets provides clues of how Earth came into being.
The studies were published on Tuesday by the US journal Science, coinciding with the meeting in Cambridge of solar system specialists from the American Astronomical Society and Britain's Royal Astronomical Society.
All rights reserved. © 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.
Subscribe To SpaceDaily Express
History's Greatest Comet Hunter Discovers 1,000th Comet
Greenbelt MD (SPX) Aug 19, 2005
One thousand comets have been discovered to date using the Solar and Heliospheric Observatory (SOHO) spacecraft. The SOHO spacecraft, a joint effort between NASA and the ESA, has accounted for approximately one-half of all comet discoveries with computed orbits in the history of astronomy.
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.|