On December 5th, 2020, the Japanese Aerospace Exploration Agency’s (JAXA) Hayabusa 2 mission sent a sample capsule home containing debris from the near-Earth asteroid (NEA) 162173 Ryugu. This was the culmination of the probe’s first six years in space, which launched in Dec. 2014 and rendezvoused with Ryugu in June 2018. While the probe sets its sights on its new targets, scientists will be busy analyzing the Ryugu sample.
One thing they noticed immediately after opening the shell on Monday (Dec. 21st) was the black sandy dust that lined the capsule’s outer shell. According to a statement issued by JAXA, the black sand is material taken from the surface of Ryugu. Considering what’s inside sample chamber A, it appears that the amount of material obtained by Hayabusa 2 is more substantial than previously thought.
This discovery comes just a week after the mission’s re-entry capsule returned to Earth. It and the sample it contained were recovered in Woomera, Australia on Dec. 6th, 2020, after entering the atmosphere and creating a bright streak in the sky. By Dec. 8th, the capsule was delivered to the JAXA Sagamihara Campus, where technicians began the process of carefully removing the sample.
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On Dec. 14th, the agency confirmed in a statement that a sample of grains of black sand thought to be from the asteroid was found inside the sample container. They apparently became attached to the entrance of the sample catcher, the container in which the samples were stored. JAXA also released a picture of what the sooty material looked like (shown above). As they stated:
“JAXA has confirmed that samples derived from the asteroid Ryugu are inside the sample container. We were able to confirm black, sand-like particles which are believed to be derived from the asteroid Ryugu. We will continue our work to open the sample-catcher within the sample container. Extraction of the sample and analysis of it will be carried out.“
A day later, JAXA released two statements. The first announced confirmation that the samples obtained had indeed come from the asteroid Ryugu. The second statement shared the results of an analysis performed on gas that was also present in sample container A. After conducting mass spectrometry tests at the Quick Look Facility (QLF) – which was established on Dec. 7th, 2020 at the Woomera Local Headquarters – JAXA has confirmed that the gas originated from the asteroid.
To confirm the initial results, a similar analysis was conducted at the Extraterrestrial Sample Curation Center (ESCuC) on the JAXA Sagamihara Campus on Dec. 10th and 11th. These tests produced the same result, indicating that the gases are indeed the result of material obtained as part of the Ryugu sample that sublimated during transport back to Earth.
This is the first time that a sample return has included material from deep inside a deep-space object, not to mention material from said object that was in a gaseous state. JAXA also indicated in their second statement that the analysis team will continue examining the gaseous sample and perform “a detailed analysis of the molecular and isotopic composition of the collected gas.”
In the meantime, JAXA will “continue with opening sample chambers B and C within the sample container, and the sample will be removed and analyzed by the curation group and initial analysis team,” they said. These samples include both surface dust and pristine material from below the surface that was kicked up by an impactor fired from the probe (which was essentially an anti-tank warhead).
While it was in orbit around Ryugu, Hayabusa 2 also deployed four small rovers – including MASCOT and Minerva-II – to the asteroid’s surface to investigate and analyze the geological context of the samples collected. Due to the minimal gravity and extremely uneven surfaces involved, these rovers were designed to hop their way around rather than rely on legs, wheels, or treads.
These samples are our first glimpse of a sample-return mission that was six years in the making and the successor to the Hayabusa mission – which rendezvoused with asteroid Itokawa in September of 2005 and returned a sample to Earth by June of 2010. Then and now, the purpose of these missions is to study material leftover from the formation of the Solar System (which is what asteroids essentially are).
In addition to revealing things about the earliest periods of the Solar System, the surface and interior of these asteroids are also a record of its subsequent evolution over the past 4.5 billion years. To obtain samples from Ryugu, Hayabusa 2 had to travel about 300 million km (200 million mi) from Earth to rendezvous with the NEA Ryugu as it was passing beyond Earth’s orbit.
Once all of Hayabusa 2’s samples are removed and analyzed, half of them will be shared between JAXA, NASA, and other international organizations. The rest will be kept for future study as advances in technology allow for more detailed analyses and studies. Meanwhile, Hayabusa 2 is now moving to rendezvous with its next targets as part of its mission extension.
This extension was granted in September of 2020 to include the tholin-rich (reddish colored) asteroid 2001 CC21 and the water-rich NEA 1998 KY26, which is believed to be composed of material from multiple asteroids that collided in the past. The probe will make flybys of these asteroids in July of 2026 and July of 2031 (respectively).
Beyond revealing things about the history of our Solar System, these icy asteroids could tell us how water was distributed among the planets billions of years ago (thus making life possible)!