An Asteroid, Cobbled Together

Three years ago, the Japanese spacecraft Hayabusa set out to fetch a bit of asteroid and return it to Earth, and last November, the little satellite set down on a 500-meter-long asteroid called Itokawa. But Hayabusa's trip has been every bit as bumpy as the asteroid itself, and mission scientists remain unsure whether the beleaguered probe collected a sample or will even make it back home. Still, the spacecraft did manage to transmit some eye-popping findings, described in today's issue of Science: Gravitational measurements taken with Hayabusa's instruments indicate Itokawa is up to 40% empty space. Hayabusa means falcon, but the spacecraft has labored along more like a wounded duck. On the way to Itokawa, it lost two of three gyroscopelike devices that controlled its orientation, so researchers had to fire thrusters that pushed it off course. When Hayabusa finally reached Itokawa, it released a small rover into space instead of dropping it on the asteroid (ScienceNOW, 14 November 2005). Then it failed to fire its bulletlike probe into the surface, leaving researchers wondering if it had retrieved a sample or not (ScienceNOW, 14 December 2005 ). To top it off, mechanical and communications problems have waylaid Hayabusa, so if it returns home, it won't be until 2010, 3 years behind schedule.

Nonetheless, data already beamed back to Earth have given researchers unprecedented insights into asteroids. Itokawa is a surprisingly loose agglomeration of boulders, stones, and even sand, hanging together in a lumpy, collision-induced shape resembling a potato, Hayabusa's science team reports. Some parts of Itokawa are smooth, "almost like a sea of desert sand," says team member Daniel Scheeres, an aerospace engineer at the University of Michigan, Ann Arbor. So, it's possible the asteroid's surface remains active, shifting and contorting because of its gravity's tenuous hold.

The Hayabusa data reveal how an asteroid could consist of a bunch of rubble, Scheeres says. "This is the first real example we have that clearly shows distinct components resting on each other in a seeming jumble. Thus, it provides a lot of insight into the mechanical features and properties of such bodies."

But questions remain. "Just looking at the pictures, with very few impact craters and lots and lots of boulders--that's puzzling," says planetary scientist Clark Chapman at the Southwest Research Institute in Boulder, Colorado. Equally unexpected are the presence of large and uniform areas of pea-gravel-sized material, he says. "There are forces at work here that we'll have to figure out," Chapman says. "There's lot more thinking that's got to be done."

Japan is a sleeping superpower. Hayabusa was launched by a Japanese M-5 rocket, a design copied from America's Peacekeeper ICBM. From wikipedia:

There are concerns that the development of this three-stage solid fuel rocket, unusual for space exploration, is motivated by military concerns despite Japan’s non-nuclear policy. Solid fuel rockets are the design of choice for military applications as they can remain in storage for long periods, and then reliably launch at a moments notice.

Your have read Tom Clancy's Debt of Honor, haven't you? This type of development is a big part of the "evil industrialist's" plot to have Japan punish the United States for what they did to his family in WW2. Big difference is they use Russian designed ICBM plans bought from the collapsing Soviet Union for their secret ICBMs. Good read, maybe even the best of his books, but if you read it make sure you also pick up Executive Orders. It's basically part 2 of one HUGE novel.

You need to do a little more homework, such as looking at the link I provided. The author at that site has a PhD in Astrophysics from Yale, and is the former director of the Naval Observatory. He probably knows a bit more "basic physics" than you do.

The difference between an age of 65 million years and 4.5 billion is so substantial as to qualify the first as "new" and the last as "old." There is no way to use the observations made by Hyabusa to differentiate between these two ages.

In fact, another article on the asteroid posted at NewScientist.com implies that the asteroid could well have been the product of a planetary breakup rather than congealing from primordial debris:

Rubbly Itokawa revealed as 'impossible' asteroid

19:00 01 June 2006
NewScientist.com news service

Maggie McKee

Measurements of the asteroid's gravity field combined with size data show Itokawa is an astonishing 40% empty space (Image: JAXA)Related ArticlesNew data reveals mysteries of asteroid Itokawa

20 March 2006

The small asteroid Itokawa is just a loosely packed pile of rubble that collected after a collision between asteroids, according to a slew of new studies based on data from Japan's Hayabusa spacecraft. The asteroid appears to be plagued by recurring impacts and tremors today, making its continued survival a mystery.

Hayabusa made two attempts to collect samples from the 535-metre-long space rock in November 2005. The attempts appear to have failed, but that will not be clear unless the spacecraft can be returned to Earth, which scientists are hoping to do in 2010. But during its approach, the spacecraft did take images and other data on Itokawa's topology, composition and gravity field.

What they found was completely unexpected. "Five years ago, we thought that we would see a big chunk of monolithic rock, that something so small doesn't have the ability to hold onto any pieces," says Erik Asphaug, a planetary scientist at the University of California in Santa Cruz, US, who is not involved with the mission. "Everything we suspected about it turned out to be wrong."

The spacecraft showed a surface littered with boulders and gravel, suggesting it was made of the debris from a larger asteroid that was shattered in a past collision. The latest observations from Hayabusa put an approximate size limit on that parent body.

Hot heartOnboard gamma-ray and infrared spectrometers reveal the asteroid is composed of the "raw materials" of planets, such as olivine, pyroxene and metallic iron, says Asphaug. But these materials do not appear to have melted and separated, as would be expected if the parent body was larger than about 200 kilometres across, he says.
Nonetheless, Hayabusa's cameras reveal that some large boulders appear layered, "like you'd broken off a rock from the side of a river bed," he says.

That suggests Itokawa's parent body was large enough to heat up at its centre and develop some internal structure, even if it wasn't large enough to melt. "There could have been hydrothermal processes conducting water around, similar to on Earth, where steam passes through rocks and alters their compositions," he told New Scientist.

Measurements of the asteroid's gravity field also suggest it coalesced from the debris of a previous collision. Hayabusa scientists used the data - combined with measurements of the space rock's size - to estimate its density. It appears to be 40% porous, or filled with empty space.

"That is astonishing," says Asphaug, adding that a handful of sand has a porosity of 20%. "It's very hard to get porosities greater than that. You've got to start balancing things delicately, like you were building a house of cards," he says. "The only way to do it is to gently pack the stuff together."

Tamping downBut that raises another mystery, he says, since repeated impacts with other space rocks over millions of years should have made Itokawa denser. "Every time you have an impact, you're going to tamp it down," he says.

And Itokawa certainly appears to have had its share of cosmic run-ins, even though it does not show many craters. New craters are thought to be buried by gravel that flows into them when Itokawa shudders after being struck by a space rock. This shaking is also thought to have buried the powdery dust created in such impacts, leaving only larger boulders and gravel-sized rocks visible.

Only one other asteroid has been studied so extensively, a 33-kilometre-long rock called Eros. That asteroid appears to be a single piece of rock, but its density is more like a rubble pile. Asphaug argues that more asteroids should be visited by spacecraft, in part to determine what sort of threat they might pose if they struck the Earth.

Itokawa does cross the Earth's orbit during its 1.5-year-long path around the Sun, but calculations show it will probably never hit the planet. But Asphaug says an asteroid the size of Itokawa is expected to strike the Earth once every 100,000 years, making robotic - or even human - missions to asteroids a priority. "You want to be ahead of the game" in the event that an asteroid is found on an impact course, he says.

Journal reference: Science (vol 312, p 1328 to 1353)

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