AAAS, Science Make Landmark Engagement with Japan

Asteroid Itokawa

The 2 June issue of Science, a special issue on the space mission to the Asteroid Itokawa, was an auspicious landmark in the journal’s history: The first special issue focusing on original, peer-reviewed research primarily by Japanese scientists. AAAS, the journal’s publisher, supported that effort with its first jointly organized press conference in Tokyo related to a forthcoming Science paper.

The briefing by mission scientists from the Japan Aerospace Exploration Agency (JAXA) drew more than two dozen journalists from Japan’s top newspapers and broadcast stations—and generated extensive news coverage of the Japanese scientists’ pioneering success in understanding the structure and composition of near-Earth asteroids.

The reporters gathered at JAXA headquarters in Tokyo also heard Science Editor-in-Chief Donald Kennedy’s congratulatory message for the Hayabusa mission.

“As the first mission designed to travel into deep space and bring back samples of an asteroid, Hayabusa has been a trail-blazing success,” Kennedy said in a letter read at the briefing by Dennis Normile, the veteran Japan correspondent for Science. “If pieces of the asteroid Itokawa make it back to Earth in 2010, that will be a further triumph. Even now, however, this ambitious mission is providing us with many crucial lessons on how to plan and execute the sample-return missions of the future.”

The 2 June issue of Science contained the first-peer-reviewed results from the mission—seven research papers from the JAXA team, headed by Akira Fujiwara, that guided the Hayabusa craft.

Asteroid Itokawa, named after Japanese rocket scientist Hideo Itokawa, was chosen as Hayabusa’s target in part because it is one of the most common types of rocky near-Earth asteroids, the so-called S-type asteroids. The relatively tiny asteroid is only 500 meters—or about 1,800 feet—long.

Hayabusa, which means "falcon" in Japanese, hovered over Itokawa last fall, taking up-close measurements and photographs. Then, in November, it swooped down for a brief landing and the first-ever sample attempt on an asteroid. The touchdown took place on a smooth patch called "Muses Sea." (This is a play on words; Hayabusa was originally called MUSES-C).

Fujiwara and his colleagues report that asteroid Itokawa has two parts, a smaller "head" and larger "body," giving it the shape of a sea otter. Unlike previously explored asteroids, Itokawa’s surface has patches of both rough, boulder-strewn terrain and "seas" of uniformly sized, finer gravel particles, which appear velvety-smooth in the photographs from the mission. Itokawa appears to consist mostly of rubble.

Asteroid structure has been a puzzle for scientists. In theory, because of the pummeling that asteroids receive by other objects, they should be clusters of fragments that have re-accreted. Previously studied asteroids, however, generally appear to be lumps of solid rock.

“Although it is still unknown why these other asteroids do not show a rubble pile structure, at least now we have the first example of a rubble-pile asteroid,” said Fujiwara.

The rubble is very loosely packed and porous, just barely held together by the asteroid’s own gravity. If an object collided with Itokawa, it would probably be like a rock landing in a bucket of sand. The signs of impacts with small space rocks get erased as the rubble shifts after the impact, so there are very few craters on Itokawa.

The asteroid’s head-and-body structure might have arisen as the rubble shifted in response to impacts. Or, the head and body may once have been separate rubble piles that gradually merged.

Because it was designed to take samples from its destination and return them to Earth, the Hayabusa mission has also offered important engineering lessons. JAXA has described Hayabusa as “a technology demonstration spacecraft focusing on key technologies that are required for future large-scale sample and return missions.”

The spacecraft used an electronic ion propulsion system, whose efficiency should be critical to future missions in deep space, and autonomous navigation technology for its delicate approach and landing. Hayabusa also attempted a "touch and go" sampling effort intended to bring the first asteroid material back to Earth, but it may not have been successful.

The spacecraft, now low on fuel, is slowly gliding back to Earth, where it may drop its cargo capsule into the Australian desert in 2010.

The mission encountered several major technical difficulties, which Erik Asphaug of the University of California at Santa Cruz notes in a Perspective article that accompanies the research.

“Despite these heartbreaking setbacks, Hayabusa has been a stunning success for asteroid science and deep space concept testing, as reported in an exciting set of mission reports in this issue,” Asphaug writes. “These are the culmination of heroic efforts to make things go right in the face of multiple setbacks. Failures are not uncommon in deep space, and in this case ingenuity and perseverance paid off in remarkable ways.”

The Tokyo news briefing was organized by the AAAS Office of Public Programs, in conjunction with AAAS Chief International Officer Vaughan Turekian and ASCA Corp., which does the weekly translation of Science paper summaries for journalists into Japanese.

Reporters from the Tokyo-based Asahi Shimbun and Japan Broadcasting Corp. (NHK), among others, spent more than two hours listening to reports by members of the JAXA team and asking them questions.

Hiroshi Masumitsu, a science correspondent in the Washington, D.C., office of the Tokyo-based Yomiuri Shimbun, sees the publication of the Hayabusa research in Science and the AAAS/Science news briefing in Tokyo as important events for a Japanese S&T community that is looking to expand its global engagement.

“Japanese researchers have been urged for a long time to make more effort to disseminate their work internationally,” Masumitsu explained in email remarks after the briefing. “Of course there is a language barrier for the Japanese, but many important achievements were published only in Japanese research journals and were not translated into English in the past. Some have said that this lack of distribution is to blame for the fact that Japan has had very few Nobel laureates.

“I remember that research by Japanese scientists and engineers did not appear often in Science when I became a science writer in 1992,” Masumitsu added. “But now I can find Japanese researchers’ names in Science almost every week. So I think the special issue of Science was one of the milestones that proved the internationalization of Japanese science and technology.”

Since 1949, nine Japanese researchers have won the Nobel Prize in the sciences—four of them between 2000 and 2002.

In remarks prepared for reporters at the Yomiuri Shimbun, the world’s largest-circulation newspaper, Science Deputy Editor Brooks Hanson said the journal was honored to publish the Hayabusa research.

“More than 40 percent of all papers published in Science have corresponding authors located outside of the United States, including many from Japan,” Hanson said. “We have worked regularly with Japanese authors. But, to our knowledge, this is the first special issue of Science focusing on original, peer-reviewed research primarily by Japanese scientists. It is exemplary, exciting work that is helping answer many important questions about near-Earth asteroids and the early solar system in which they formed…. It is also pioneering a new approach to space missions.”

Kennedy echoed those sentiments in his remarks read at the briefing.

“Thank you for entrusting this important research for publication in the journal Science,” Kennedy said. “Thanks also for effectively communicating the research to the public. It is an honor to be publishing this research, which is evidence of Japan’s thriving space-science initiatives and the quality of Japanese research overall.”

Kathy Wren and Edward W. Lempinen

6 June 2006