1. Count of Potentially Hazardous Asteroids Grows to 200...11/14/99
2. Leonids on the Moon...11/03/99
3. Near Earth Asteroid Prospector (NEAP) Asteroid Rendezvous Launch Period: 3 April 2001...09/26/99
4. Probe Captured Asteroid Science Data...08/05/99
5. NASA Captures Images Of Asteroid...08/02/99
6. Spacecraft Begins Transmitting Infrared Images Of Asteroid...07/31/99
7. NASA Probe Heads To Asteroid Flyby...07/29/99
8. NASA Unveils Plans For Comet...07/09/99
9. JPL'S New Deep Impact Asteroid Mission Ok'd By NASA...07/08/99
10. Meteor Crater, Arizonia Created By An Asteroid, Shock Melt...07/02/99
11. Say Hello to Comet C/1999 H1 (LEE)...06/12/99
12. Hale-Bopp: A cosmic leftover...03/19/99
13. Asteroid Eros apparently solid, smaller than expected...02/11/99
14. NASA tracks comet "Wild-2"...02/04/99
15. NASA footage shows asteroid in motion...01/27/99
16. Great ball of fire Flash in sky likely exploding meteor...1/11/99
17. Argentina extinctions linked to asteroid...1/8/99
18. January's Chilly Meteors - The 1999 Quadrantids...12/28/98
19. Space probe sends new asteroid pictures...12/26/98
20. Scientists regain contact with NEAR asteroid probe...12/24/98
21. NEAR Spacecraft to Flyby Asteroid Eros today...12/23/98
22. NEAR Near Earth Asteroid Rendezvous ... 12/21/98
23. NASA's NEAR spacecraft may find that asteroids need dusting ... 12/16/98
24. Scientist claims to have found part of deadly asteroid ... 11/19/98
25. NASA to inspect meteorite shower for signs of life ... 11/16/98

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Meteor Crater, Arizonia Created By An Asteroid, Shock Melt...07/02/99

By: Lori Stiles, The University of Arizona

Scientists Discover That Most Of The Asteroid That Formed The Meteor Crater Was Shock Melted.

TUCSON, ARIZ. ? Most of the asteroid that blasted Meteor Crater out of the Colorado Plateau melted, according to new evidence released today by an international team of scientists. This new finding contradicts a previously held theory that the Canyon Diablo meteor vaporized and gives a glimpse of what happens when similar-sized meteors slam into Earth every 6,000 years or so.

Meteor Crater, near Winslow, Ariz., the best-preserved impact crater in the world, was formed 50,000 years ago -- just yesterday on the geological time scale. Although modest by geological standards -- the equivalent of a 20-to-40 megaton bomb -- it grabs our attention because of its close proximity to our own time and for the story it tells about what could happen again.

The bowl-shaped depression measures 1.2 kilometers (four-fifths of a mile) wide and 180 meters (570 feet) deep and scientists say events like this occur every 1,600 years, with a Canyon-Diablo-sized meteor slamming into a land mass every 6,000 years. In research published today (July 2) in Science, scientists conclude that more than four-fifths of the Earth-crossing asteroid completely melted and spread over the Four Corners Region where Colorado, Arizona, New Mexico and Utah meet.

Most of the iron asteroid, which was 30 meters (100 feet) or more in diameter, spread as an enormous expansion plume produced by gases released from Colorado Plateau limestone. A fraction of the melted material survived to form sand-grain-sized particles called "spheroids." By using complex measurements of radioactive nickel 59 and computer modeling, the researchers determined the probable depth within the asteroid at which these spheroids were formed. Their experimental measurements and modeling results indicate that Canyon Diablo was travelling faster on impact that previously believed.

The scientists include faculty members from Rutgers University, The University of Arizona in Tucson, Australian National University, University of Rhode Island and University of California-Berkeley. Keith Fifield of the Australian National University, led the team in systematically measuring long-lived radioisotope nickel 59 in Canyon Diablo meteorites and spheroids. Nickel 59 is a "cosmogenic nuclide" produced in space when cosmic rays penetrate objects containing nickel 58. Nickel 58 changes to nickel 59 by absorbing an extra neutron from cosmic radiation.

Fifield used accelerator mass spectrometry to make the measurements. Canyon Diablo meteorites contain seven times more nickel 59 than do recovered spheroids, meaning they had come from the surface or outer shell of the asteroid, where exposure to cosmic radiation is greatest, said Greg Herzog of Rutgers University. Scientists find nickel 59 to be a far more useful cosmogenic nuclide for such analysis than some more commonly used ones. That's because of the mechanism by which it forms, its long half-life (76,000 years), its low volatility and its resistance to weathering, team members add. Elisabetta Pierazzo, a post-doctoral researcher at the UA Lunar and Planetary Laboratory, used numerical models to simulate the impact.

The simulation, based on models developed at Sandia National Laboratories, factored in the size and composition of Canyon Diablo and its target. Pierazzo determined which parts of the Earth-smashing asteroid remained solid and which melted and became spheroids. This was done by using experimentally measured shock pressure values for melting iron/nickel alloys. The composition of these alloys is close to that of meteorites. The team concludes that the precursor material of the spheroids probably came from depths of 1.3 to 1.6 meters (four to five feet) beneath the surface of the meteor before it entered Earth's atmosphere.

Pierazzo says that only about 15 percent of the rear, outer part of the asteroid remained solid after impact and that the other 85 percent of the projectile melted. She bases this conclusion on combined observational, experimental and theoretical evidence. Impact velocities by Earth-crossing asteroids average around 15 to 20 kilometers per second. The 20 km/s velocity -- or 45,000 mph -- would produce a melting profile that agrees with the experimental measurements, she said. At lower velocities, a much larger fraction of the projectile would have remained solid, leaving behind far more meteorites. "The model really makes sense when you match it with the hard evidence," Pierazzo said. "The modeling confirms the experimental results that say the Canyon Diablo meteorites came from the outer part of the projectile, and the spheroids from a depth of 1.5 to 2 meters below the surface. "I feel confident that this impact was at higher velocity than many people have believed it to be," she added. "This work gives no evidence for vaporization. From what we know about shock pressure, melting and vaporization of iron, the model indicates little or no vaporization of the impact."

Say Hello to Comet C/1999 H1 (LEE)...06/12/99

A MILLENNIUM GROUP SPECIAL REPORT

Earl L. Crockett, Writer http://www.millenngroup.com/repository/cometary/lee.htm

Hale-Bopp: A cosmic leftover...03/19/99

(AP) - Comet Hale-Bopp, which blazed across the sky in 1997, may be brimming with some of the primordial material from which the sun and the planets formed more than 4 billion years ago.

California Institute of Technology scientists who tuned radio telescopes onto the comet's nucleus as it cut across the solar system found vents spewing a volatile mixture of gas and dust into space.

The images suggest that 15% to 40% of Hale-Bopp's mass is pristine interstellar material, while the rest has been transformed extensively during the comet's passage through space.

The images are among the finest ever obtained of a comet with radio telescopes.

The findings were published in Thursday's issue of the journal Nature.

Comets are often called dirty snowballs. Most orbit far from the sun in the deep freeze beyond Pluto's orbit. That enables them to remain virtually unchanged over billions of years.

"Nothing has changed much out there since that time. Therefore it's a way of sampling some of the chemistry, or very close to what it was, when the solar system formed," said Paul Weisman, a scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, who was not involved in the work.

The CalTech researchers found two icy jets erupting with forms of primordial deuterium-hydrogen, the poisonous gas hydrogen cyanide and a form of hydrogen called heavy water. The material may be rising from deep within the comet, said Geoffrey Blake, a CalTech professor of cosmochemistry and planetary sciences.

Actual proof that comets contain the primordial material of the solar system may have to wait until a spacecraft can dig inside one.

A NASA probe that is set for launch in 2003 will try to do that for the first time ever in 2006. If it survives the landing, it will drill into Comet Temple 1 to sample what's inside.

Asteroid Eros apparently solid, smaller than expected...02/11/99

(CNN) Eros isn't as grand as had been expected, NASA scientists studying the asteroid said Monday. Also known as asteroid 433, Eros was studied by the Near Earth Asteroid Rendezvous satellite in late December. NASA said Eros was found to be slightly smaller than predicted, with at least two medium-sized craters, a long surface ridge and a density comparable to the Earth's crust.

NASA tracks comet "Wild-2"...02/04/99

The Stardust spacecraft is set to blast off for an historic rendezvous with Comet Wild-2 This weekend a NASA spacecraft will blast off from the Kennedy Space Center for an historic rendezvous with periodic comet Wild-2. Its ambitious goal is to intercept Wild-2 in 2004, to capture tiny bits of comet dust and debris, and then return them to Earth for analysis in 2006. Stardust is the first comet rendezvous mission since since the European Giotto spacecraft's fly-by of Halley in 1986, and the first ever to attempt to return a comet sample to Earth. It's a long, 7-year mission, but one most scientists feel is worth the wait. Right: Comet P/Wild-2 photographed by K. Meech on Dec. 17, 1990 using an 88 inch reflector telescope on Mauna Kea, Hawaii. Scientists are curious about comets because they are thought to be the oldest, most primitive bodies in the solar system. Comets are made up of the same stuff as the early Solar Nebula that collapsed to form the sun and planets. It is now known that comets contain significant amounts of water ice, dust, and carbon based compounds. They may have been an important source of water and organic molecules for Earth when many comets collided with our planet during a period of heavy bombardment over 4 billion years ago. Modern-day comets are like a time machine. They offer a window into the past when the Solar System was young and life on Earth was just beginning.

NASA footage shows asteroid in motion...01/27/99

(CNN) -- Humankind will have to wait at least another year to see the first closeup views of an asteroid. But in the meantime, NASA has released some unprecedented footage of one of the mysterious space rocks as it rotates slowly in the solitude of space. The NEAR spacecraft captured a series of images of 430 Eros as it flew within 2,320 miles (3,830 km) of the asteroid on December 23. Presented in sequence, the images show Eros, a very elongated, cratered object about 18-by-eight miles (30-by-14 km) across, rotating with a period of just over five hours. The movie shows about two-thirds of a rotation of Eros. The first view, taken at 10:44 a.m. EST from a range of 7,150 miles (11,890 km), shows about half of the dayside of Eros. The movie ends at 2:05 PM EST, just after closest approach, when only a tiny portion of the dayside of Eros is visible. During the movie, the spacecraft's view of the asteroid changed dramatically. As is the case with most asteroids, Eros is rotating uniformly about a fixed axis, and is not tumbling randomly through space. NEAR had been scheduled to begin orbiting Eros in February, but the rendezvous was delayed for a year after the spacecraft's main engine shut down during a series of crucial firings on December 20. In a matter of hours, mission controllers were able to program an alternate command sequence that put the spacecraft on a trajectory about 2,500 miles (4,100 km) from the surface of the asteroid. However, plans to orbit Eros -- the first such attempt in history -- were postponed until February 2000. NEAR was one of the first NASA robot crafts built under a program that emphasizes less expensive and more effective ways of exploring the universe. It cost $129 million to build, and the entire mission so far has stayed within its planned budget of $211.5 million. Launched in February 1996, NEAR is to spend almost a year orbiting within 9 miles (15 km) of the surface of the potato-shaped asteroid. If the spacecraft succeeds in orbiting Eros, it then is expected to possibly land on its surface. Scientists hope the mission will provide answers to fundamental questions about the nature and origin of near-Earth objects, such as the numerous asteroids, meteoroids, and comets in the vicinity of Earth's orbit.

Great ball of fire Flash in sky likely exploding meteor...1/11/99

By ELIZABETH MANNING Daily News reporter

A brilliant flash and earthshaking boom noticed by thousands of Alaskans late Friday were likely a meteor exploding in Earth's atmosphere, scientists said Saturday. Donald Martins, an astronomy professor at the University of Alaska Anchorage, wasn't lucky enough to see the object that streaked blue, green and red across the Southcentral Alaska sky. But based on witness accounts, Martins and other scientists believe the flash came from a meteor or comet fragment - probably the size of a pumpkin - that exploded about 50 miles above Earth's surface. "That's almost certainly what it was," Martins said. "They aren't uncommon. But it is very rare to have one explode and hear it."

Dozens of people phoned authorities late Friday to report the event, which happened about 10:25 p.m. Most eyewitnesses described a brilliant and colorful flash, followed several minutes later by a boom. The boom was so loud it shook houses in Palmer and Wasilla and was heard from South Anchorage to Sutton and beyond. "I wish I could describe it," said Gina Gilmore, who watched the fireball from a hot tub near Palmer. "It was an eerie blue and green color and lit up the whole area. Then we heard an explosion, and it stilled our conversations." Gilmore said she thought at first that the object was a shooting star or meteor, but its intensity made the group in the hot tub wonder: Could it have been a missile, an electrical explosion or something from the "X-Files"?

"It was greenish, and it was loud," said Rachael Wagner, 16, another observer from Wasilla. She was inside her home and noticed the flash through the window. Assuming the object was a meteor, Martins said, it's possible that the fireball was part of the Quandrantid meteor shower, which was expected to be active from Dec. 28 through Thursday.

On Tuesday, Anchorage residents reported an object streaking low in the sky across the backdrop of the Chugach Mountains. The Quandrantids are one of the year's most intense meteor showers but are among the least observed because of their location high in the Northern sky. The meteors appear to emanate from the obsolete constellation Quadrans Muralis, hence the name Quandrantids. Though the origin of the Quandrantids is unknown, most meteor showers are caused by fragments of comets - dust and ice debris - that boil away from a comet's nucleus when it passes close to the sun.

A meteor shower results when Earth passes through a comet's debris stream. Martins said most meteors burn up from friction as they enter Earth's atmosphere. When the chunks are large enough, they sometimes explode because the core of the object is much cooler than the outside. "Imagine a cold rock coming in and getting very hot," said Greg Durocher, a scientist with the U.S. Geological Survey. "It's under tremendous stress." Durocher and other observers of the fireball said they heard the boom about three or four minutes after they saw the flash.

Based on that information, Martins estimated that the object was about 50 miles away at the time of the explosion. The noise people reported may have been a sonic boom. However, a single noise heard at the same time by everyone would indicate an explosion, he said. Martins said he once heard of a fireball so loud it almost deafened several fishermen in the South Pacific.

Although the object may have been fairly large for a meteor, Martins said, it is unlikely that anyone will find a meteorite, which is a fragment of a meteor that falls to Earth. There were rumors Friday of objects striking the Parks Highway at Mile 141 and reports by pilots of debris falling, but meteorites are extremely hard to find, Martins said. "Unless you can actually determine where the impact occurred, you're worse off than finding a needle in a haystack," he said. And if the object was part of a comet, Martins said, most of the fireball was probably composed of ice, which would have melted before hitting the ground. Martins said the colors people described suggest that the fragment was part of a comet. "It had a good tail on it," Gilmore said. "And it was amazing to watch it going across the sky. I probably won't ever see that again."

* Reporter Elizabeth Manning can be reached at emanning@adn.com

Argentina extinctions linked to asteroid...1/8/99

(ENN) An asteroid or comet that crashed into Argentina some 3.3 million years ago led to a regional climate change and the disappearance of 36 types of animals, according to a study published in the Dec. 11 issue of Science. The impact may have directly caused the regional extinction or triggered a climate change that led to the disappearance of the animals in what is now southeastern Argentina. "Unlike what impacts did to dinosaurs and other prehistoric creatures, this was not an event that led to global extinctions," said principal investigator Peter Schultz, professor of geological sciences at Brown University and an impact specialist. "We've found something linked to much more recent land history. The advantage to studying something this young is that you can really examine the forensics."

"This is a threshold event. It may have been just large enough to cause regional damage and extinctions and may have triggered a climate change. El Niño or a volcanic eruption produces small tweaks to the climate compared to what one of these impacts can do." The cyclical cooling of the Earth's temperatures that began soon after the impact 3.3 million years ago continues today, he said.

January's Chilly Meteors - The 1999 Quadrantids...12/28/98

(NASA) One of the year's most intense meteor showers, the Quadrantids, begins tonight. The shower stretches from Dec. 28 through Jan. 7 with a sharp maximum on Jan. 3, 1999. The Quadrantids are the only major annual meteor shower whose source, presumably a comet or an asteroid, remains unknown. Readers are invited to observe the upcoming shower and to submit their data for analysis by scientists studying the structure and origin of the Quadrantid meteoroid stream.

Space probe sends new asteroid pictures...12/26/98

(CNN) -- Space scientists began the daunting task Thursday of interpreting hundreds of pictures taken by a robotic space probe that completed its planned flyby of the asteroid Eros on Wednesday.

The images of the giant space rock will provide scientists with valuable information on the size, shape and surface characteristics of Eros and whether it has any moons, officials said. The Web site for the Near Earth Asteroid Rendezvous started posting the mages on Thursday as they were being processed.

A montage of the first nine images shows Eros completing nearly half a rotation. The smallest resolved detail is approximately 1650 feet (500 meters) across. Scientists were still trying to determine why they lost contact with the spacecraft for 27 hours and why it shut itself down during a series of engine firings Sunday that would have put it on course to reach Eros next month. Within hours, mission controllers were able to program an alternate command sequence that put the spacecraft on a trajectory about 2,500 miles (4,100 km) from the surface of the asteroid.

Scientists regain contact with NEAR asteroid probe...12/24/98

They are not telling us all the story, hairs are up on this one!... Mitch

(CNN) -- To the relief of mission controllers, a robot spacecraft tracking a giant asteroid phoned home Tuesday following a mysterious 27-hour blackout. But its much-anticipated mission to orbit the space rock called Eros has been postponed, possibly until spring.

NEAR Spacecraft to Flyby Asteroid Eros today...12/23/98

A Dec. 20 spacecraft abort of the initial rendezvous burn of the Near Earth Asteroid Rendezvous (NEAR) spacecraft has resulted in a postponement of NEAR’s orbit of asteroid 433 Eros, originally scheduled for Jan. 10, 1999. However, a flyby of the asteroid is planned for Dec. 23, 1998, at 1:43 p.m. EST, that will provide valuable information for its later study.

.“While the engine burn abort was unfortunate, we still expect to accomplish the rendezvous objectives, but at a later date,” says NEAR Mission Manager, Dr. Robert W. Farquhar, of The Johns Hopkins University Applied Physics Laboratory, which manages the NASA mission. “We expect that the later rendezvous date will not diminished the overall science return.”

During the Dec. 23, 1998, flyby, scientists will gain a preview look at the asteroid and gain a global perspective that will provide important information in planning an orbit insertion. Mission designers are now expecting the rendezvous will take place by May 2000. Data obtained from the flyby will help determine the shape and size of the asteroid and if it has any moons.

The rescheduling of the NEAR mission was made necessary by the abort of a planned 20-minute engine burn on Dec. 20, 1998. The spacecraft aborted just seconds after initiation of the bipropellant burn, causing communications with the spacecraft to be lost for about 27 hours. Contact was reestablished early Dec. 22, after NASA’s Deep Space Network locked onto a radio signal from the NEAR spacecraft at about 8 p.m. EST, on Dec. 21.

Responding to a command from the Mission Operations Center, NEAR started downloading stored data early Dec. 22, which the mission team has been analyzing to determine the cause of the abort and why the spacecraft lost attitude control.

“We’ve looked at the data and we believe there has been no damage to the spacecraft or the propulsion system,” says spacecraft systems engineer, Andrew G. Santo. “Our fault protection software identified the problem and switched NEAR to a safe mode. Essentially, it worked as designed.”

During the Dec. 23 flyby NEAR will take approximately 500 images from as close as 4,100 kilometers (2,500 miles). Although the images will be of lower resolution than those taken June 27, 1997, during the flyby of asteroid 253 Mathilde, they will provide scientists with important information about the asteroid.

NEAR will then travel in an orbit around the sun that nearly matches that of Eros. In May 2000, the spacecraft and Eros will meet, making it possible to insert NEAR into orbit around the asteroid

NEAR was launched Feb. 17, 1996 as the first launch of NASA’s Discovery Program. Updates of mission activities and science returns will be posted on the Web site

http://near.jhuapl.edu.

NEAR (Near Earth Asteroid Rendezvous...12/21/98

Spacecraft will initiate a series of rocket engine firings that accelerate it toward a rendezvous with a faster-moving asteroid, 433 Eros. NEAR will reach Eros next month to begin the first close-up and comprehensive study of an asteroid in space history. "This is the first time ever a spacecraft will orbit an asteroid," said Professor William V. Boynton of the Lunar and Planetary Laboratory at The University of Arizona in Tucson. "There have been flybys and snapshots, but not much in the way of quantitative scientific data." Boynton is on one of six science teams that will study 433 Eros on the year-long NEAR mission that begins on Jan. 10 and is scheduled to end Feb. 6, 2000. The asteroid, which measures 24 miles in length and 10 miles in diameter (40 kilometers x 17 kilometers) was the first near-Earth asteroid (those whose orbits come close to or cross the orbit of Earth) spotted by astronomers. Boynton is a scientist on the X-Ray/Gamma Ray Spectrometer, or XGRS, experiment. It is the primary experiment for determining the elemental composition of the surface and layers just beneath the surface. The instrument will begin taking data next spring while NEAR is orbiting above the asteroid's surface, coming as close as 9 miles (15 kilometers).

NASA's NEAR spacecraft may find that asteroids need dusting...12/16/98

NASA scientists think that asteroids scoop up dust from space over the eons, possibly blanketing themselves in layers up to a meter thick. Asteroids are too small for gravity to capture dust, but static electricity might do the job instead. If this idea is correct, then asteroids could provide storehouses of primordial matter from the early Solar System for future exploration.

Scientist claims to have found part of deadly asteroid...11/19/98

(CNN) For years, the scientific community has theorized that a giant cosmic "impactor" slammed the Earth 65 million years ago in what is now Central America, wiping out the dinosaurs and much of the rest of life on the planet. UCLA scientist Frank Kyte has analyzed a small piece of a fossilized meteorite excavated from the North Pacific Ocean and contends it must have broken off from the asteroid when it shattered on impact. Kyte said the tiny iridium-and-iron chip in his sample makes it "highly" likely that the rock came from that asteroid.

NASA to inspect meteorite shower for signs of life...11/16/98

WASHINGTON (Reuters) - Researchers looking for extraterrestrial life will examine next week's Leonid meteorite shower for clues, NASA said Friday. Governments and companies with satellites orbiting Earth are worried and many have turned them so dust and fragments do not damage their delicate equipment. But other scientists view the shower of extraterrestrial material as a chance to see what other-worldly stuff is made of and NASA will send up two research aircraft to study the dust trail. The Leonids come from dust and debris tailing the comet Tempel-Tuttle, which orbits the Sun every 33 years. Earth crosses through the trail every November, but once in 33 years this dust is very heavy and causes a bright meteorite shower.