Deep impact comet mission

<body leftmargin="0" bgcolor="#000060" text="#FFFFFF" link="#FFFF00" vlink="#FF9900"> <b> <p class="MsoNormal"><font face="Arial" size="5">IMPACT! Scientists blast projectile into comet</font></p> </b> <p class="MsoNormal"><font face="Arial" size="1">July 4, 2005<br> Special to World Science<br> </font> <font size="2" face="Arial"> <b> <br> </b> </font> <b><font size="2" face="Arial"> Scientists shot a washing machine-sized projectile into a comet, eight times faster than a rifle bullet. The impact created an enormous blast visible on images sent back to Earth, and whose size surprised even some mission scientists.</font></b> </p> <p class="MsoNormal"><b><font size="2" face="Arial">NASA researchers confirmed the impact at 1:58 a.m. Eastern U.S. time, in a project designed to better understand what comets are made of.</font></b></p> <p class="MsoNormal"><b><font size="2" face="Arial">A sequence of images sent back by cameras on the projectile revealed growing amounts of detail on the rocky-looking comet as a huge crater came to view. Later, images showed a bright blast showering off the speeding, potato-shaped object.</font></b></p> <p class="MsoNormal"><b><font size="2" face="Arial">Now, the task of analyzing the images and other data from the mission begins.</font></b></p> <p class="MsoNormal"><b><font size="2" face="Arial">Some scientists predict the blast will reveal organic material in the comet—the types of molecules that characterize life. Others say the mission could provide information on how comets could serve as water-supply and fueling stations for future space travelers.<br> <br> “We want to find out what are the guts of a comet,” said mission principal investigator and University of Maryland astronomer Michael A’Hearn.<br> <br> The impact is supposed to eject ice, dust and gas from the crater and reveal the pristine material beneath. This is believed to be material left over from the Solar System’s formation 4½ billion years ago.<br> <br> The nature of the blast could reveal how soft or hard the comet is, said Don Yeomans, a member of the Deep Impact science team. Comets are generally believed to be something like dirty snowballs, but no one is sure.<br> <br> “If the comet is solid like a block of ice, the crater will be relatively small,” he explained. But if it’s softer or more loosely packed, “like a soufflé,” he added, “we’re expecting a much larger crater,” possibly the size of an American football field. “Either way we’re going to know how a comet is put together.”<br> <br> Comets could also provide water and rocket fuel for future space travelers, he added. “Comets may well be watering holes and fueling stations for interplanetary travel,” he said.<br> <br> The $330 million NASA mission took off with the Jan. 12 launch of a spacecraft the size of a subcompact car, carrying a copper projectile the size of a washing machine. <br> <br> Twenty-four hours before the planned July 4 impact, the spacecraft shot out its projectile. The comet and projectile were to come together at 37,000 kilometers (23,000 miles) per hour, well over eight times faster than a speeding rifle bullet. <br> <br> The flyby craft was designed to send back pictures of the event, and data from spectrometers—instruments that analyze light to provide information on the types of molecules in the comet.<br> <br> Space-borne observatories were also watching, including include NASA’s Hubble and Spitzer space telescopes and the Chandra X-ray Observatory, as were observatories on Earth. The impact was visible from Earth telescopes between Arizona and New Zealand, scientists said.<br> <br> The projectile will be far too small to appreciably change the comet’s trajectory, they added, comparing the impact to a pebble hitting a truck. The comet is believed to be about half the size of Manhattan.<br> <br> The flyby craft was to release its projectile when it and the comet were about 83 million miles (134 million km) from Earth, a distance slightly less than that between the Sun and the Earth.<br> <br> Researchers with Cardiff University in Cardiff, U.K., predicted that the impact results will bear out their theory that comets contain organic matter. Some scientists believe organic material deposited by a comet could have produced life on Earth and other planets.<br> <br> “The outer crust of the comet will consist of asphalt-like material with permafrost beneath. The small icy fragments blasted out by the impact will include organic matter,” the Cardiff researchers said in a statement last week.</font></b></p> <p class="MsoNormal"><b><font size="2" face="Arial">The blast experiment “will show, we believe, that a comet is not a rubble pile, nor a conglomerate of ices, but a porous mass of organics and ice under the black asphalt crust,” said Cardiff Professor Chandra Wickramasinghe. He added that the comet may contain biological material similar to some that’s found in the Arctic.<br> <br> Although scientists want to learn about the comet’s interior, they also want to better understand the evolutionary changes in its mantle, or upper crust. <br> <br> This is one reason they picked Tempel 1. Discovered in 1867 by Ernst Tempel, it has made many passages through the inner solar system, orbiting the Sun every 5.5 years. This makes Tempel 1, otherwise a fairly typical comet, a good target to study evolutionary change in the mantle, researchers said.<br> <br> Astronomers believe Tempel 1 comes from the Kuiper belt, a disc-shaped region of comets and asteroids that lies beyond Neptune’s orbit and extends out for several hundred times the Earth-Sun distance. </font></b></p> </body>