Explanation: Why are parts of this asteroid’s surface so smooth? No one is yet sure, but it may have to do with the dynamics of an asteroid that is a loose pile of rubble rather than a solid rock. The unusual asteroid is currently being visited by the Japanese spacecraft Hayabusa that is documenting its unusual structure and mysterious lack of craters. Last month, Hayabusa actually touched down on one of the smooth patches, dubbed the MUSES Sea, and collected soil samples that will eventually be returned to Earth for analysis. Unfortunately, the robot Hayabusa craft has been experiencing communications problems and so its departure for Earth has been delayed until 2007. Computer simulations show that 500-meter asteroid Itokawa may impact the Earth within the next few million years.

Credit & Copyright: ISAS, JAXA Explanation: Where are the craters on asteroid Itokawa? No one knows. The Japanese robot probe Hayabusa recently approached the Earth-crossing asteroid and is returning pictures showing a surface unlike any other Solar System body yet photographed — a surface possibly devoid of craters. One possibility for the lack of common circular indentations is that asteroid Itokawa is a rubble pile — a bunch of rocks and ice chunks only loosely held together by a small amount of gravity. If so, craters might be filled in whenever the asteroid gets jiggled by a passing planet — Earth in this case. Alternatively, surface particles may become electrically charged by the Sun, levitate in the microgravity field, and move to fill in craters. Over the weekend, Hayabusa lowered itself to the surface of the strange asteroid in an effort to study the unusual body and collect surface samples that could be returned to Earth in 2007.

Credit & Copyright: ISIS, JAXA

Explanation: What’s that unusual looking spot on asteroid Itokawa? It’s the shadow of the robot spacecraft Hayabusa that took the image. Japan’s Hayabusa mission arrived at the asteroid in early September and has been imaging and maneuvering around the floating space mountain ever since. The above picture was taken earlier this month. Asteroid Itokawa spans about 300 meters. One scientific goal of the Hayabusa mission is to determine out how much ice, rock and trace elements reside on the asteroid’s surface, which should give indications about how asteroids and planets formed in the early Solar System. A can-sized robot MINERVA that was scheduled to hop around the asteroid’s surface has not, so far, functioned as hoped. Later this month, Hayabusa is scheduled to descend to asteroid Itokawa and collect surface samples in a return capsule. In December, Hayabusa will fire its rockets toward Earth and drop the return capsule down to Earth’s Australian outback in 2007 June.

By
NewScientist.com news service
Maggie McKee

Japan’s Hayabusa spacecraft successfully completed a practice approach to asteroid Itokawa on Wednesday after a previous “dress rehearsalâ€? failed on 4 November. Mission managers have now set dates for three more rendezvous with the space rock in an effort to return the first-ever asteroid samples to Earth in 2007.

On 4 November, mission officials called off the first rehearsal descent with the probe still 700 metres away from the asteroid because it had trouble identifying its landing site. The rehearsal was meant to test autonomous landing technologies in advance of two sample-collecting touchdowns and release a robot called Minerva that will hop around the asteroid, snapping images and measuring temperatures.

But mission officials say they have now identified the problem and successfully descended to within 70 metres of the 600-metre-long asteroid on Wednesday. They will retry the rehearsal descent – and release Minerva – on 12 November, then attempt sample collection landings on 19 and 25 November.

No specific information has been released concerning the problem or its solution, but on 7 November Hayabusa’s project manager Jun’ichiro Kawaguchi told New Scientist: “We had difficulty accurately guiding the spacecraft.”

He said the problem was “deeply related” to the loss of two of its three stabilising reaction wheels in July and October 2005. Since then, the craft has been using its single remaining wheel and onboard hydrazine fuel thrusters to keep itself oriented.

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Source: New Scientist Space