Hayabusa – Dust From Itokawa – III

The issue of the journal Science from 26 August 2011 vol 333 pp 1113-1131 has six articles on the Hayabusa sample return mission from the asteroid Itokawa. The first article is discussed here, the second here, and this is the third:

Neutron Activation Analysis of a Particle from Asteroid Itokawa

A single grain from the Hayabusa mission has been analyzed by instrumental neutron activation analysis (INAA). The grain was mainly olivine, with minor amounts of plagioclase, troilite and metal.

This grain was one of the largest returned by the Hayabusa mission. The scanning electron microprobe (SEM) results show this to be a large crystal of olivine. Small pieces of silicate were attached to the surface. Radioactive analysis indicates that the grain is relatively homogeneous.

Comparison of the INAA analysis of this grain from Itokawa with from an LL6 chondrite (St Severin) and an L6 chondrite (Modoc) indicated an elemental abundance discrepancy.

Iron (Fe) and Scandium (Sc) abundance can be determined reliably, and the ratio is determined by the differentiation of iron into the core of a body during its formation. In particular, the Fe/Sc ratios from the Earth, Moon, Mars and 4Vesta are lower than those of chondrites. The ratios from Itokawa are higher than those from terrestrial olivine, and are thus from an extraterrestrial origin. This increases confidence that Hayabusa did return samples from Itokawa.

Nickel (Ni) and Cobalt (Co) typically diffuse into a metal phase. The ratio of Ni/Co in bulk chondrites plot along a line with carbonaceous chondrites. Samples from the Earth’s crust are relatively depleted in Nickel compared to Cobalt, and thus are distinguished from the grain returned from Itokawa.

In addition, Iridium (Ir) abundances were estimated, and the result indicates that the sample must have condensed from a fractionated nebula gas where refractory siderophiles such as Iridium had already condensed and been removed.

Hayabusa – Dust From Itokawa – II

The issue of the journal Science from 26 August 2011 vol 333 pp 1113-1131 has six articles on the Hayabusa sample return mission from the asteroid Itokawa. The first article is discussed here, and this is the second:

Oxygen Isotopic Compositions of Asteroidal Materials Returned from Itokawa

The first article in this series established that the major mineral assemblages of the asteroid Itokawa are olivine, pyroxene, plagioclase, iron sulfide and iron-nickel metal.

Minerals within bodies of the Solar System have unique oxygen isotope ratios, thought to be determined by gas-dust chemistry and accretion physics. However, the Earth and the Moon are the only bodies for which isotope ratios are known.

Twenty-eight (28) of the sample grains returned by Hayabusa were analyzed for oxygen isotope abundances. The ratios were compared to the ordinary chondrite meteorite Ensisheim (an LL-6 chondrite) and Earth minerals, and the uncertainty in measurements were calibrated against standard mean ocean water (SMOW) from Earth. The results show that the grains returned by Hayabusa are not of terrestrial origin. One of the Earth minerals was a fosterite crystal from San Carlos, Arizona.

Chondrites are classed as H, L or LL, and the samples from Itokawa are clearly L or LL and not H. The variation in ratios between samples indicates the degree of equilibration due to metamorphic heating. These data indicate that the samples from Itokawa experienced temperatures between 600 C and 720 C, which is lower than LL6 chondrites and higher than LL4 chondrites.

These results are consistent with those from those reported in the first paper and provide unequivocal evidence that ordinary chondrites come from S-Type asteroids.

Hayabusa – Dust From Itokawa – I

The latest issue of the journal Science (vol 333 26 August 2011 pp 1113-1131) has six articles on the Hayabusa sample return mission from the asteroid Itokawa. The first article is entitled:

Itokawa Dust Particles: A Direct Link Between S-Type Asteroids and Ordinary Chondrites

The results are from the first samples retrieved from the sample catcher. A Teflon spatula successfully swept about 10% of the sample catcher’s surface. 1534 particles have been identified with the field-emission scanning electron microscope. There were 1087 mono-mineral grains:

  • 580 olivine particles
  • 126 low Calcium pyroxenes
  • 56 high Calcium pyroxenes
  • 186 feldspars
  • 113 troilites
  • 13 chromites
  • 10 Calcium phosphates
  • 3 Iron-Nickel grains

The remaining 447 particles bear several minerals, mostly silicates.

The sample catcher was also “tapped” to retrieve additional particles. 38 of these particles have been closely examined. Six are poorly differentiated and 32 are highly differentiated. The 32 highly differentiated particles indicate they have undergone intense thermal metamorphism. There is almost complete partitioning of the Magnesium, Iron and Calcium between pyroxenes. Ordinary chondrite meteorites exhibit thermal metamorphism ranging from unequilibrated type 3 to completely equilibrated type 6. Measurements indicate that the particles formed at a peak temperature of 800 C and cooled slowly to 600 C. The slow cooling indicates that the particles from Itokawa formed at considerable depth. This suggests that the parent body was destroyed by one or more catastrophic impacts. Remnants reformed into present day rubble pile asteroids, including Itokawa.

Petrologic data from the study shows that Itokawa is an ordinary chondrite, linking these asteroids with the corresponding meteorites.

Hayabusa – The Little Spacecraft That Did.

Hayabusa
Hayabusa Sample Return
Image Credit: JAXA

The new issue of Science (15 April 2011 vol 232 p 302) discusses the current status of analyses of the samples returned from the asteroid Itokawa. It is a solid scientific success. The results were presented by Japanese scientists at the Lunar and Planetary Science Conference in The Woodlands, Texas, from 7 – 11 March 2011.

Analysis has confirmed that the S-type class of asteroids covered by a mysterious discoloration is the source of the most common meteorite that falls to Earth. Decades ago, research had suggested the composition of these asteroids was different from chondrite meteorites.

However, by 2001, Richard Binzel and others at MIT had concluded from telescopic observations that Itokawa belongs to the distinctive LL subclass of ordinary chondritic asteroids that had been “weathered” by exposure to space.

The first task was to remove any particles from the collection mechanism, which had malfunctioned in spectacular fashion. A specially designed extraction tool was a failure. A Teflon spatula was a bit better, but the best result came from striking the overturned canister with a screwdriver. 20 sharp raps did the trick. About 1500 particles from Itokawa were recovered. All smaller than 100 micrometers.

Researchers across Japan took 52 of these particles and applied a range of microanalytical techniques – XRD, XRF, UMT, FIB, TEM, SEM, EPMA and SIMS. This alphabet soup clearly showed that Itokawa was a space-weathered ordinary LL chondrite asteroid. A great win for Hayabusa.

Additional research is now underway to determine what sort of space weathering is involved in producing the discoloration.

Previous NSS Phoenix blog entries about the intrepid Hayabusa can be found at:

Asteroids and Comets Visited By Spacecraft

Emily Lakdawalla has built a montage of the nine asteroids (ten bodies) and four comets visited by human spacecraft and posted it on the blog at The Planetary Society. Beautiful work.


Montage

Asteroid and Comet Montage

Credits: Montage by Emily Lakdawalla. Ida, Dactyl, Braille, Annefrank, Gaspra, Borrelly: NASA / JPL / Ted Stryk. Steins: ESA / OSIRIS team. Eros: NASA / JHUAPL. Itokawa: ISAS / JAXA / Emily Lakdawalla. Mathilde: NASA / JHUAPL / Ted Stryk. Lutetia: ESA / OSIRIS team / Emily Lakdawalla. Halley:: Russian Academy of Sciences / Ted Stryk. Tempel 1: NASA / JPL / UMD. Wild 2: NASA / JPL.

Let us know what you think. What do you want to know about? Post a comment.

Hayabusa – Retrieved

The re-entry capsule from the Hayabusa mission has been found and begun its trip back to Japan for analysis. The Associated Press reports:

The capsule was airlifted late Monday afternoon to the town of Woomera, where it would be prepared over several days for air freighting to Japan, NASA scientist Scott Sandford said by telephone from the scientists’ base in Woomera.

Sandford said he had not seen the capsule but that photographs indicated it had made a soft desert landing.

Once back in Japan, the capsule will be transferred to a containment lab where it will be opened. It will be a considerable time before the contents are known and analyzed.

Capsule Retrieved
The Re-entry Capsule from Hayabusa.
Image Credit: AP

Capsule Retrieved
The Capsule and Parachute from Hayabusa.
Image Credit: JAXA

If the capsule does contain fragments of the asteroid Itokawa, it would be the first sample from an asteroid. Three other extraterrestrial sources have provided samples. Both the United States and Russia have returned samples from the Moon. The US did it during the Apollo manned lunar program, and the Russians did it using robotic sample and return spacecraft with its Luna program.

The second source came from the American Stardust probe, which was launched on February 7, 1999. It flew past comet Wild 2 on January 2, 2004 and collected samples from the comet’s tail. The capsule re-entered the Earth’s atmosphere and landed on January 15, 2006 in Utah’s Great Salt Lake desert.

The third source was the Genesis spacecraft. The United States launched Genesis on August 8, 2001, and crash-landed on September 8, 2004, after sampling the Solar Wind from beyond the orbit of the Moon.

An extended discussion by the BBC can be found in their Science and Environment section.

Hayabusa – Recovery

When last we left our intrepid explorer, she had returned her capsule to Earth, nevermore to be seen or heard.

The capsule, however, has been found during the night in the Australian Desert. It will be recovered in the afternoon.

It is 8:00 PM in Phoenix, and Noon in Tokyo. So according to the tweet, things should be heating up with the recovery effort. Sometime in the next six hours, we should get news on the actual recover. Then it will be off to the lab for the painstaking analysis. Did we get anything back from Itokawa?

And finding the heat shield components would be nice.

Lastly tonight, there are the offspring to be considered: Hayabusa-2


Capsule

Hayabusa return capsule and parachute.
Image Credit: JAXA Recovery Team

JAXA is now considering a mission named Hayabusa-2 This is a similar mission as Hayabusa that will return samples of surface from an asteroid to the earth. Target asteroid, however, is different. Asteroid Itokawa explored by Hayabusa is rock-rich S-type one. Asteroid that Hayabusa-2 will visit at is a C-type asteroid. C-type asteroids are also rocky, but it is thought that their rocks contain much more organic matters. Hayabusa-2 will challenge very interesting objectives: what are original organic matters existed in the solar system?; and how they are related to life?

A little after midnight Phoenix time this morning, JAXA reported it had recovered the Hayabusa re-entry capsule, and that several hours earlier had found both the front and back shells from the heat shield.