When the Hayabusa2 probe took to the skies in December 2014, it was the start of a mission that would ultimately make history. Set on a path towards an asteroid circling the Sun, the craft finally approached the minor planet – given the name of Ryugu – in summer 2018. And, incredibly, after Hayabusa2 encountered Ryugu, it eventually got close enough to transmit some truly stunning images – including the first ever to have been taken from the exterior of an asteroid.
Eight years before Hayabusa2 snapped that pioneering photo, though, its mission was given the green light by the Japanese government. And as the craft’s name suggests, it was a successor to the original Hayabusa probe, which had embarked on a similar – if somewhat problem-strewn – journey back in 2003.
This time, however, the Japan Aerospace Exploration Agency’s (JAXA) objective for this follow-up probe was to take materials from Ryugu that could potentially give insight into the very origin of life on Earth. It was hoped, too, that the findings gleaned from the mission could ultimately provide a better comprehension of both the Solar System’s beginnings and how it has changed and developed over the millennia.
Naturally, then, in order to carry out its duties, Hayabusa2 took along several different science payloads, including a quartet of cameras to be used for remote sensing and three separate instruments to help pick up those all-important samples. Also in tow were four traveling devices that were intended to traverse the surface of Ryugu when the craft arrived at the asteroid: Rover-1A, Rover-1B, Rover-2 and the Mobile Asteroid Surface Scout, which is otherwise known as MASCOT.
And one of Hayabusa2’s main features also served to set it apart from its predecessor. For this particular mission, the craft would boast an impactor – a nearly 12-inch-wide explosive device that was designed to be shot onto the asteroid’s surface. It was important that the impactor would blow up, too, as Hayabusa2 would subsequently be able to mine materials from beneath Ryugu’s facade.
Then, when the impactor was fired on April 5, 2019, it worked just as hoped by producing a crater on the asteroid. Mind you, that was far from the first stage of Hayabusa’s mission. In fact, the craft had reached Ryugu nearly a full year earlier on June 27, 2018.
Then, on September 21, 2018, Rover-1A and Rover-1B were launched towards Ryugu. The tiny devices were specifically designed to operate in the asteroid’s low-gravity environment, and they both utilized a rather unusual method of getting from A to B: principally, by hopping.
Fortunately, both rovers successfully landed on Ryugu, after which they began to acquire data from the surface of the minor planet. And this involved snapping photos – including the pioneering shot that was taken right on top of the asteroid. Not all of these efforts were successful, though. In fact, one of the first batch of pictures was so out of focus that scientists knew it must have been taken while the rover was mid-hop.
Next to visit Ryugu was the diminutive MASCOT, which left the confines of Hayabusa2 on October 3, 2018. This device took photos, too, and its first picture showed a remarkably clear and detailed vision of the asteroid itself. With a battery life of only 16 hours, however, MASCOT had to come up with findings about Ryugu relatively quickly.
It helped, though, that MASCOT was able to transmit valuable data even before touching down on Ryugu. Yes, while still roughly 167 feet from the surface of the asteroid, the rover’s magnetometer picked up information that may have been of great interest to the researchers back on Earth.
Karl-Heinz Glaßmeier – one of those who worked on MASCOT – would later reveal exactly what had been discovered. “The measurements show the relatively weak field of the solar wind and the very strong magnetic disturbances caused by the spacecraft,” Glaßmeier was quoted as saying in a 2018 press release by the German Aerospace Center.
But while JAXA had planned to collect initial samples from Ryugu in late October 2018, this feat ultimately had to be postponed. You see, the three rovers had previously indicated to the team that the asteroid was strewn with boulders – making settling Hayabusa2 safely a trickier prospect than had previously been envisioned.
The JAXA workers knew, for example, that it would be hazardous to have Hayabusa2 land in a region where the boulders were taller than around 19 inches. For one, the craft needed to be at a slight angle when landing. And given that the sampler horn was roughly 39 inches in length, a misjudged touchdown could run the risk of a large boulder damaging the craft itself.
In the end, though, the sampling was delayed for an even longer period than JAXA had initially intended, with the first collection of material taken from the surface of Ryugu on February 21, 2019. A bullet had previously been shot into the asteroid in order to kick up dust into the atmosphere and thus make the fine powder easier to accumulate.
Then, on April 5, 2019, Hayabusa2 deployed its impactor – leading, of course, to a mini-explosion on the face of Ryugu. And what the blast revealed in its wake was certainly intriguing. According to mission supervisor Makoto Yoshikawa, an image taken of the resultant crater seemed to suggest that some of the matter coating the exterior of Ryugu was “obviously different” to that found on other areas of the asteroid.
Finally, in July 2019, Hayabusa2 landed on Ryugu for a second time in order to gather the material that had been made available by the impactor explosion. And when the craft successfully garnered samples from inside the asteroid itself, it was a landmark breakthrough for JAXA.
JAXA’s Yuichi Tsuda attested to the importance of the moment, too, during a press conference that was held following Hayabusa2’s touchdown. The project manager said, “We’ve collected a part of the solar system’s history. We have never gathered sub-surface material from a celestial body further away than the Moon. We did it, and we succeeded in a world first.”
Specifically, Tsuda was hopeful that Hayabusa2 could acquire so-called “ejecta” from the impactor explosion, as what he termed “extremely attractive materials” would likely be in the vicinity. This task – among the final phases of Hayabusa2’s mission – was a very important one, too, as anything that the craft harvested could very well end up advancing scientific knowledge.
Fortunately, Hayabusa2 managed to retrieve debris from the crater, and these samples are scheduled to come back down to Earth in a capsule in December 2020. After that, researchers around the globe will be able to study the asteroid matter in detail – perhaps yielding some crucial insights into our universe in the process.
And, as previously mentioned, Hayabusa2 had followed in the wake of its predecessor, which had visited the asteroid Itokawa in 2005. But while the original Hayabusa craft was also able to collect some materials from the surface of a minor planet and subsequently bring them back to Earth, the mission didn’t completely go as hoped.
Hayabusa was a pioneer, in fact, as it was the first craft of its kind to have been made specifically to touch down on – and then leave – an asteroid. It should be noted, though, that Hayabusa’s makers didn’t intend for it to properly land on Itokawa. Instead, it was built merely to graze the face of the rock with a tool that was intended to collect sample materials.
And as it happens, Itokawa wasn’t the mission’s original destination – although that was just one of many glitches that ended up plaguing the whole endeavor. Even before Hayabusa was sent into the atmosphere on May 9, 2003, there were technical difficulties that the scientists at JAXA had to overcome.
Initially, Hayabusa was scheduled to visit the asteroid 4660 Nereus on a mission that was due to begin in July 2002. Following a rocket malfunction, however, the launch was postponed. And owing to this setback, a new asteroid therefore needed to be targeted, with scientists ultimately plumping for Itokawa.
Then the team at JAXA had to overcome yet another hurdle with Hayabusa’s payload. To start with, you see, the craft was supposed to transport a rover named Muses-CN. Muses-CN had been the work of NASA researchers, who had come up with a device that was both small and relatively lightweight – coming in at less than three pounds.
However, as Muses-CN was ultimately deemed too expensive and was therefore put on hold by NASA, the JAXA mission controllers had to change tack and use a MINERVA lander instead. Yet, in hindsight, this may actually have been a blessing in disguise, as the MINERVA-held Rover-1A and Rover-1B were subsequently used with great success on Hayabusa2.
Regardless, worse was to come after Hayabusa had finally launched, as a solar flare managed to impair the craft’s solar cells – with this in turn limiting the effectiveness of its ion engines. Thanks to this unforeseen mishap, then, there was yet another delay. Now, Hayabusa wouldn’t touch down on Itokawa until September 2005 – three months or so behind schedule.
And as Hayabusa needed to make its return to Earth in June 2010, that left it with even less time in which to complete its mission. In fact, as a result of the shortened schedule, it was impossible for the projected three landing attempts to go ahead as planned; only two were now achievable.
Then, when MINERVA was deployed from Hayabusa, it was hoped that the device would neatly descend onto the face of Itokawa, where it would gather much-needed data. Sadly, though, the rover never made it. It simply floated away from the asteroid and became lost in space – never to return.
Yet more woes followed for the Hayabusa team after an unsuccessful attempt to launch the craft’s probe. And while Hayabusa reached the surface of Itokawa on two occasions in November 2005, it transferred into safe mode both times – further depleting its chances of ever collecting matter from the asteroid.
Hayabusa actually entered safe mode for separate reasons on each of the two landing attempts. During the initial touch-down effort, for example, an obstruction in the craft’s path caused it to try to abort its mission. As Hayabusa was too close to its target at that juncture, though, it instead traveled towards the asteroid in safe mode – and without going on to garner any samples.
Then, during the subsequent attempt, Hayabusa was plunged into safe mode following an issue with the thruster system. And, yet again, the craft was stopped from launching the small missiles that should have thrown up ejecta for sampling. In total, Hayabusa was on the asteroid’s surface for just half an hour, and there was still no suggestion that it had even picked up any suitable material from Itokawa.
And yet that’s far from all that went wrong. Perhaps most perilously of all, three of Hayabusa’s quartet of engines had stopped working by November 4, 2009, leaving its chances of returning to Earth in the balance. This potentially mission-ending conundrum therefore forced JAXA to think creatively in order to get the ailing craft home.
But, thankfully, the JAXA team succeeded in the task at hand by joining parts of two malfunctioning engines together. While one of the engines was unable to expel electrons – crucial for avoiding any electrical charge accumulating on the craft – the Japanese scientists managed to salvage the situation by repurposing the neutralizer from another piece of apparatus.
That said, project manager Jun’ichiro Kawaguchi wasn’t sure whether the fix would ultimately work. Indeed, in late November 2009 he told New Scientist, “This new configuration is very new to us, and we are not sure… how much we can count on [it].” Ultimately, though, a mission that had had more than its fair share of trials and tribulations ended in some success.
Upon re-entry into the Earth’s atmosphere, Hayabusa broke up and exploded into flames, leaving the samples to float down to the ground in a heat-proof capsule. Yes, as it turned out, the beleaguered craft had gathered materials from Itokawa, and these were subsequently collected from their landing spot close to the Australian town of Woomera.
Portions of soil were taken from the surroundings, too, as researchers needed to be sure that the asteroid matter had not been tainted by any materials on Earth. That wasn’t all, either, as a further 12 months were then devoted to finding ways in which the Itokawa samples could be looked at without the risk of contamination.
What Hayabusa had collected, though, was small: just 1,500 or so particles from the asteroid that it had investigated. And as a consequence, JAXA had to embark on the delicate process of splitting these fragments in order to determine their composition. This work was conducted at Spring-8 – a synchrotron radiation facility that had been partly founded by the Japan Atomic Energy Research Institute.
These particles were also incredibly tiny, with most coming in at just 10 micrometers – or less than a ten-thousandth of an inch – each. Then, as the samples were examined, it was discovered that they were made up of minerals including pyroxene, olivine and plagioclase. And it seemed that the dust from Itokawa was apparently extremely old to boot.
According to Tohoku University researcher Tomoki Nakamura, the material that had been collected by Hayabusa may have previously laid undisturbed on the face of the asteroid for a full eight million years. Interestingly, too, studies undertaken by Nakamura and his colleagues suggest that Itokawa had once been part of a much larger asteroid that had broken up after a massive collision.
So, while the original Hayabusa mission may have been littered with various mistakes and errors, it nevertheless expanded our understanding of asteroids and the universe at large. Plus, of course, Hayabusa paved the way for Hayabusa2, which was much more of a success story. And to the general public, perhaps the most memorable things about Hayabusa2 are the wonderful images that the rovers managed to capture on the surface of Ryugu.