Recently there has been much talk about the process and ethics of moving materials that may be subject to later analysis and scrutiny into ‘secure storage.’ But the quarantining of assets such as, shall we say ‘electronic data,’ is not the only target of enhanced protection and safeguarding. In fact, around 195 million miles from us here on Earth, Hayabusa-2 – an asteroid explorer – is busy moving its precious cargo into secure storage as it begins the final leg of its 6-year mission by returning to Earth’s gravity. Hayabusa, which in Japanese means ‘Peregrin falcon,’ is returning after a rendezvous with asteroid, Ryugu, a primitive carbonaceous near-Earth object that is part of the Apollo group. Measuring just over a half mile in diameter, the diminutive body was discovered in 1999 and given the provisional designation 1999 JU3. In 2015, it was officially named ‘Ryugu’ meaning Dragon Palace – a mythical undersea palace in a Japanese folktale.
But what do Japanese folktales, asteroids, and mythical underwater abodes have to do with contamination control? Let’s take a look…
In April this year, Hayabusa-2 – a compact, refrigerator-shaped craft – detonated a Small Carry-On Impactor (SCI) on the surface of Ryugu, a C-class asteroid. The point of the blast was the creation of a new, artificial crater from which to collect samples of materials – potentially water and organic compounds – deep within the rock. Moving to a safe distance to await surface settling, the probe returned in July, hovering above a landing marker in order to fire a shot to break through the surface crust and collect the resulting debris through an extended sample tube. Among those watching the mission carefully was none other than celebrity astrophysicist Dr. Brian May, sometimes better known as the lead guitarist of the rock band Queen who, along with colleague Claudia Manzoni, had worked on creating stereoscopic images of the surface of the asteroid. Other interested parties included teams from the Japan Aerospace Exploration Agency, or JAXA, who’d pioneered the sampling and capsule storage parts of the mission and were delighted to pronounce the mission ‘a success, a big success.’(1) But why was the collection of this sort of rock sample – as opposed, for instance, to the collection of surface materials – so important to the researchers of the Hayabusa-2 project? It’s a question of contamination control…
Asteroids, small planetary bodies, exist in all reaches of our solar system. Those closer to the sun are subject to sufficient warmth that they undergo geological changes and transformations, whereas those in colder climes retain more of the original matter from which our solar system, and hence our own planet, was formed some 4.6 billion years ago. While we are better able to extract samples from nearer asteroids, we can still strive for more intact materials and retrieving rocks from below the surface of the asteroid is an obvious way to achieve this goal. Indeed as T. Yada, lead author on the paper ‘From Hayabusa to Hayabusa 2: Present Status and Plans of Curatorial Works for JAXA’s Asteroidal Sample Return Missions’ explains, the ‘[m]ajor advantages of the returned samples by missions compared with meteorites and cosmic dust found on the Earth are contamination control against the terrestrial environment and identification of their sampling bodies and positions.’(2)
But maintaining the integrity of a clean sample also requires stringent control measures once the rocks hit terre firma in 2020 in the Woomera Prohibited Area (WPA) of the outback desert of South Australia.
To that end, the Astromaterial Science Research Group (ASRG) at JAXA has leveraged its experience and on-going work in the handling of materials returned by the original Hayabusa mission. ASRG has installed custom developed sterile chambers that use ultra-pure nitrogen or an ultra-high vacuum in order to prevent exposure to our atmosphere and terrestrial particulate matter. The chambers are housed within a better than class 1000 cleanroom environment where particles as small as 10-300µm are collected using an electrostatically controlled micro-manipulator and transferred via sealed sample holders – which look like square glass petri dishes – for cataloging at JAXA. The cleanroom also contains a clean bench, microbalance, transportable vacuum system, gloveboxes, and nitrogen desiccators. The instruments housed within the chambers and the wider cleanroom environment are available solely to researchers within the ASRG to prevent contact with any materials not directly related to the sample analysis.
At time of writing, more than 700 particulate samples from the original Hayabusa mission have been described and logged within the agency’s database. For the samples returned by this second mission, JAXA has developed a suite of five new clean chambers – three of which use vacuum processes with the other two using purified nitrogen. Upon the successful return of Hayabusa 2, JAXA’s plan is to unseal the sample container within the first chamber, a vacuum-sealed area, and extract the sample catcher. Step two is to transfer the catcher to the next sealed chamber to be opened for sample retrieval. In the third chamber, the catcher will be ‘purged in purified nitrogen’ before being sent to one of the two final chambers for observation via optical microscope, weighing, measuring, and all subsequent analysis.(3)
And what will we learn from analyzing these fresh samples?
In truth, scientists are not yet sure. In a CNN article published in April this year, Professor John Bridges of the University of Leicester, UK, is quoted as believing that the mission ‘will throw up some unexpected results,’ that could re-shape the current paradigm on the formation of the solar system.(4) Carbonaceous asteroids such as Ryugu are the best extraterrestrial sources of materials such as ice, minerals, and organic compounds that interact with one another in ways that are relevant to studies of the origins of life here on our own home planet. And surely any mission that furthers our understanding of the conditions under which life here evolved is worth pursuing.
Or is it?
Just as a small thought experiment – what if the samples from asteroid Ryugu suggest a bleak future for our own small blue planet? What if they contain elements detrimental to our survival? Bolstered by the theory of panspermia, we have long romanticized the idea of other life forms existing with us in the desolation of the universe. So what if mining these asteroid samples cracks open that particular Pandora’s Box, unleashing upon our fragile world an enemy we would not know how to fight? Perhaps this is the moment to return to the Japanese folk story…
As we know, nomenclature for the two Hayabusa missions drew upon the legend of Urashima Tarō for inspiration. But what was the narrative and, furthermore, what was its moral? According to the story, a fisherman – Urashima Tarō – once saved a sea turtle from attack and released it back to the ocean. As thanks, the turtle who was, in reality, a princess disguised as an amphibian, invited Tarō to visit her undersea palace, in which he stayed for three days. Upon leaving to return to land, the princess gifted him a treasure box, Tamatebako, which she warned him never to, open. Once back in his village, Tarō discovered to his dismay that centuries had passed and all that he knew was gone. In shock and bewilderment, he opened the box, smoke poured out, and he was instantly transformed into an old man. While the tale exists in differing versions, each one is consistent in depicting the results of opening the treasure box: the protagonist immediately ages and dies. According to Japanese Info, an online portal to Japanese travel and culture, the moral of the story is open to a broad spectrum of interpretation.(5) Perhaps the message is that time waits for no-one and that man must ultimately perish. Perhaps it conveys the idea that good deeds do not necessarily occasion a reward. Or maybe the takeaway is simpler: ‘You can’t go home.’
But there is also another interpretation of the tale’s meaning and it is common to both the Japanese legend and that of Pandora and her infamous box: Not all knowledge is inherently worth pursuing and ignorance can indeed be bliss. Let us only hope this is not the case with Hayabusa-2…