Japanese scientists complete inventory of Ryugu asteroid samples

In a press conference yesterday the Japanese space agency JAXA announced that scientists have completed their inventory of the samples brought back from the asteroid Ryugu by the Hayabusa-2 spacecraft, and are now ready to begin distributing those samples to scientists around the world for more detailed research.

JAXA has cataloged the soil samples brought back by Hayabusa 2 last December, by size, color and shape. From now, 269 researchers from 14 countries, including Japan and the United States, will conduct an in-depth analysis of the soil’s structures and components over the course of about a year.

As expected, the inventory found the samples had a large amount of hydrogen, oxygen, and carbon atoms. Even before Hayabusa-2’s arrival, Ryugu had been catalogued as a “hydrated” asteroid, which means it was thought to contain a lot of hydrogen and oxygen, the basic elements of water. The inventory has now confirmed this.

Ryugu’s most primitive boulders

In a just published paper scientists reveal how they think they have identified the oldest rocks on the rubble pile asteroid Ryugu, and found them to be distributed across the entire face of the asteroid.

These boulders are light enough that they would float on water.

Ryugu is thought to have initially formed as a fluffy planetesimal that coalesced from accumulated dust in the early Solar System, and subsequently underwent processes such as thermal evolution and compression. This parent body was then later destroyed in a collision and fragments of this reaccumulated into the asteroid. However, planetesimals have never been seen, so whether they really existed or what they may have looked like is one of the biggest challenges in understanding the planet formation process. The boulders discovered in this research are thought to be a material that most strongly retains the appearance of the fluffy planetesimals that triggered the birth of the planets in the Solar System.

Additionally, the data from all the scientific instruments onboard Hayabusa2 that were used to examine the surface of Ryugu revealed that fragments of material similar to those of the ultra-high porosity boulders are globally distributed over the asteroid surface, and may have been collected in the sample taken by Hayabusa2. If highly primitive material with the ultra-high porosity discovered here is also found in the collected samples, it will both clarify the formation and evolutional history of Ryugu’s parent body, and also provide evidence of planetesimal formation in the early stage of the Solar System formation process.

There is no word yet from the scientists studying the Hayabusa-2 samples on what they have found. This paper gives them an idea of what could be the most important type of rock to look for.

Hayabusa-2 begins journey to two asteroids

On January 5, 2021, after successfully delivering its samples of Ryugu to Earth, Hayabusa-2 fired up its ion engines and began its ten-year journey to two different asteroids.

Hayabusa2’s first extended-mission destination is the roughly 2,300-foot-wide (700 meters) asteroid (98943) 2001 CC21, which the probe will fly by at high speed in 2026, if all goes according to plan. A more in-depth rendezvous with yet another space rock, 1998 KY26, is scheduled to follow in 2031.

In a previous post I had mistakenly left out the first target asteroid. However, their primary target remains the tiny 100-foot-wide 1998 KY26, since it is so small. This will be the first close-up view of such a small asteroid, in space. Since such asteroids are many, it will tell us much about the make-up and history of the solar system.

First look at Ryugu samples

Japanese scientists have taken their first look at the Ryugu sample material brought back by Hayabusa-2 and found they resemble charcoal.

The samples Japanese space officials described Thursday are as big as 1 centimeter (0.4 inch) and rock hard, not breaking when picked up or poured into another container. Smaller black, sandy granules the spacecraft collected and returned separately were described last week.

…The sandy granules the Japan Aerospace Exploration Agency described last week were from the spacecraft’s first touchdown in April 2019.

The larger fragments were from the compartment allocated for the second touchdown on Ryugu, said Tomohiro Usui, space materials scientist. To get the second set of samples in July last year, Hayabusa2 dropped an impactor to blast below the asteroid’s surface, collecting material from the crafter so it would be unaffected by space radiation and other environmental factors.

Usui said the size differences suggest different hardness of the bedrock on the asteroid. “One possibility is that the place of the second touchdown was a hard bedrock and larger particles broke and entered the compartment.”

The analysis of these samples has only just begun. Dating them is likely next, and that will probably reveal some startling results.

Samples from space!

Scientists from both the Japanese Hayabusa-2 mission to the asteroid Ryugu and the Chinese Chang’e-5 mission to the Moon announced yesterday the total amount of material they successfully recovered.

The numbers appear to diminish the Japanese success, but that is a mistake. Getting anything back from a rubble-pile asteroid that had never been touched before and is much farther away from Earth than the Moon was a very great achievement. The 5.4 grams is also more than fifty times the minimum amount they had hoped for.

This is also not to diminish the Chinese achievement, They not only returned almost four pounds, some of that material also came from a core sample. They thus got material both from the surface and the interior of the Moon, no small feat from an unmanned robot craft.

Scientists from both nations will now begin studying their samples. Both have said that some samples will be made available to scientists from other countries, though in the case of China it will be tricky for any American scientist to partner with China in this research, since it is by federal law illegal for them to do so.

Subaru Telescope photographs Hayabusa-2’s next target asteroid

In order to better constrain its orbit, the Subaru Telescope in Hawaii has obtained new photographs of Hayabusa-2’s next target asteroid, 100-foot-wide 1998 KY26.

This asteroid is predicted to approach to within 0.47 AU of Earth in mid to late December 2020, giving us a rare opportunity that comes only once every three and a half years. However, the diameter of 1998 KY26 is estimated to be no more than 30 meters, and thus its brightness is so dim that ground-based observations of the asteroid are difficult without a very large telescope.

The observations with the Subaru Telescope were conducted upon the request of the Institute for Space and Astronautical Science (ISAS), JAXA. And as a result, 1998 KY26 was photographed in the direction of the constellation Gemini as a 25.4-magnitude point of light with a measurement uncertainty of 0.7 mag. The positional data collected during these observations will be used to improve the accuracy of the orbital elements of the asteroid. Similar observations were conducted with the Very Large Telescope (VLT) of the European Southern Observatory (ESO).

If all goes right Hayabusa-2 will rendezvous with 1998 KY26 in the summer of 2031.

Scientists confirm ample Ryugu material in first Hayabuse sample chamber

Japanese scientists have opened the first chamber that stored the Ryugu asteroid samples obtained during its first touch-and-go sample grab, and confirmed that it holds ample material.

They also noted that the chamber itself contained gas from the asteroid as well.

The Japan Aerospace Exploration Agency (JAXA) has confirmed that the gas collected from the sample container inside the re-entry capsule of the asteroid explorer, Hayabusa2, is a gas sample originating from asteroid Ryugu.

The result of the mass spectrometry of the collected gas within the sample container performed at the QLF (Quick Look Facility) established at the Woomera Local Headquarters in Australia on December 7, 2020, suggested that the gas differed from the atmospheric composition of the Earth. For additional confirmation, a similar analysis was performed on December 10 – 11 at the Extraterrestrial Sample Curation Center on the JAXA Sagamihara Campus. This has led to the conclusion that the gas in the sample container is derived from asteroid Ryugu.

They think that this gas must have outgassed from the samples themselves. I suspect it was released either during the long journey or when the samples were subjected to the high accelerations and impact during its return to Earth. Research is going to have to try to pin this down, however.

They plan to open the two remaining sample chambers containing material sometime next week.

Scientists confirm Hayabusa-2’s return capsule brought back material from Ryugu

Based on their first observations of the return capsule from Hayabusa-1, Japanese scientists yesterday confirmed that it successfully has returned material from the asteroid Ryugu.

JAXA said in a statement that they observed the sandy material at the entrance of the collection chamber, but have yet to look inside to see if more asteroid dust is lurking there. It is only the second time that scientists have returned material from an asteroid.

This find in the entrance portends a gold mine of material in the collection chamber itself.

Hayabusa-2’s samples from Ryugu land in Australia

The return capsule carrying the asteroid samples grabbed by Hayabusa-2 from Ryugu successfully parachuted down in the outback of Australia today.

Officials from the Japan Aerospace Exploration Agency, or JAXA, confirmed shortly after 1 p.m. EST (1800 GMT) that the Hayabusa 2’s nearly 16-inch (40-centimeter) sample carrier landed in Australia. Touchdown likely occurred several minutes earlier.

Recovery teams dispatched via helicopter began hunting for the 35-pound (16-kilogram) capsule using estimates of its landing site derived from a radio beacon signal. Mission managers expected it could take several hours to find the capsule and recover it. The landing occurred before dawn in Australia.

Since the article above was posted the capsule was located, and it was found much quicker than first expected.

This was the second sample return mission by the Japanese. The first, Hayabusa-1, successfully returned its capsule in 2010, but because of many technical problems during the mission it only brought back a few microscopic samples. In fact, the technical problems were so bad it was really a miracle the capsule came back at all.

Hayabusa-2 however has been a complete success, showing that they learned from the first mission and applied those lessons to the second.

Hayabusa-2’s impactor shook Ryugu

When Hayabusa-2 fired an impactor into the asteroid Ryugu in order to access subsurface material in a sample grab, it apparently shook the asteroid, shifting boulders and rocks as far as 130 feet away.

The artificial impactor disturbed boulders within a 30m radius from the center of the impact crater- providing important insight into asteroids’ resurfacing processes.

Professor ARAKAWA Masahiko (Graduate School of Science, Kobe University, Japan) and members of the Hayabusa2 mission discovered more than 200 boulders ranging from 30cm to 6m in size, which either newly appeared or moved as a result of the artificial impact crater created by Japanese spacecraft Hayabusa2’s Small Carry-on Impactor (SCI) on April 5th, 2019. Some boulders were disturbed even in areas as far as 40m from the crater center. The researchers also discovered that the seismic shaking area, in which the surface boulders were shaken and moved an order of cm by the impact, extended about 30m from the crater center. Hayabusa2 recovered a surface sample at the north point of the SCI crater (TD2), and the thickness of ejecta deposits at this site were estimated to be between 1.0mm to 1.8cm using a Digital Elevation Map (DEM).

This data makes all the more important for OSIRIS-REx to get post-sample-grab images of its Nightingale site, if at all possible.

Ryugu, like Bennu, appears to have rocks from other asteroids

Japanese scientists today announced that 21 rocks identified by Hayabusa-2 on the asteroid Ryugu have a composition that suggests they were formed on another asteroid.

Although Ryugu’s surface is uniformly dark [because it is a C-type asteroid], the scientists behind the new research found numerous boulders scattered across the asteroid that were 1.5 or more times brighter than their surroundings — that is, they reflected at least 50% more light than most of the rest of Ryugu. This contrast made the researchers suspect these boulders may have come from outside the asteroid.

By analyzing the spectrum of light reflected off 21 of these boulders, the scientists deduced they were made of minerals known as anhydrous silicates. Prior studies have suggested that such water-poor, silicon-rich rocks make up silicaceous or S-type asteroids, the most common kind of asteroid found in the inner main asteroid belt. The brightness of these boulders also matches the brightness of S-type asteroids.

This result compliments the result yesterday from scientists studying Bennu with OSIRIS-REx, and was in fact released at the same time. Both asteroids apparently contain material from other asteroids, suggesting that asteroids in their initial formation (as rubble piles) are routinely a mixture of material from many asteroids, thrown out during impacts and then recaptured.

Japan chooses Hayabusa-2’s next asteroid target

The new colonial movement: It appears that Japan has chosen the next asteroid that its probe Hayabusa-2 will visit in 2031, after it releases its samples to Earth in December from Ryugu.

Japan’s Hayabusa2 space explorer will aim to probe the asteroid “1998KY26” located between the orbits of Earth and Mars in 2031 after completing its current mission of collecting samples from another asteroid, the country’s science minister said Tuesday.

It is hoped Hayabusa2 will approach the ball-shaped asteroid, which has a diameter of around 30 meters and rotates about every 10 minutes, in July 2031, Education, Culture, Sports, Science and Technology Minister Koichi Hagiuda said.

It will not obtain samples from this second asteroid, only observe it close up by camera.

Hayabusa-2’s future asteroid targets

Link here. There are two prime candidate asteroid targets, both near Earth astroids.

The possible secondary targets include the oblong asteroid 2001 AV43 or the asteroid 1998 KY 26. They’re each about the size of a large house and both orbit the Sun in roughly 500 days. The proposed plan would see Hayabusa 2 arriving at 2001 AV43 in the late 2029 time frame, or reaching 1998 KY 26 in July 2031. Both asteroids have a low enough relative speed relative to the spacecraft to put them within (eventual) reach after Hayabusa 2’s December flyby.

Interestingly, 2001 AV43 will fly 313,000 km from Earth (0.8 times the Earth-Moon distance) on November 11, 2029.

The two asteroids were selected from an initial field of 354 candidates, which was winnowed down based on accessibility and scientific interest. Both are fast rotators, as evidenced by their light curves, each spinning on its respective axis once every 10 minutes. This represents the shortest “day” of any known object in the solar system, suggesting that these asteroids are in fact solid objects and not simply loosely aggregated “rubble piles.” A visit to one of these asteroids would mark the first time a space mission has seen such an enigmatic fast rotator up close.

The asteroid 1998 KY26 is also a possible carbonaceous (C-type) asteroid, and Hayabusa 2’s exploration of such a space rock would be another first.

Going to 1998 KY26 would also require a distant pass of another asteroid. Going to 2001 AV43 would require a fly-by of Venus, which could provide more data on that planet. Based on this information, my guess is that they will opt for 1998 KY26.

The decision must likely be made before Hayabusa-2 drops off its Ryugu samples to Earth on December 6, 2020.

After releasing its Ryugu samples Hayabusa-2’s mission will continue

Japan’s space agency JAXA has revealed that it is looking at two fast-spinning asteroids as possible destinations for its Hayabusa-2 spacecraft after it has dropped off its samples from the asteroid Ryugu on December 6.

The candidate asteroids on the agency’s list are asteroid 2001AV43 which Hayabusa2 would reach in November 2029 after flying by Venus, and asteroid 1998KY26 which the probe would reach in July 2031 after passing by another asteroid.

JAXA says both asteroids are rotating on their axis once every 10 minutes. The high-speed spinning indicates that the asteroids’ inner structures are likely different from that of asteroid Ryugu on the first mission, which consists of pieces of rocks.

The spacecraft will no longer have the equipment for returning additional samples, but everything else is functioning and it has the fuel.

Evidence suggests Ryugu was once closer to Sun

The uncertainty of science: Spectral data collected of the surface of Ryugu by Japan’s Hayabusa-2 probe suggests that the asteroid once spent a period of time much closer to the Sun.

The combined data show an oddly striated world. Ryugu’s equator and poles are tinged blue and are brighter compared with its darker, reddish mid-latitudes. These color differences wouldn’t be obvious to the human eye, although the brightness changes might be.

…As Tomokatsu Morota (University of Tokyo) and colleagues write in the May 8th Science, Ryugu’s boulders likely start bluish. Then a combination of solar wind exposure, meteoroid impacts, and solar heating reddens them. This redder stuff migrates to the asteroid’s mid-latitudes over time, because topographically those are the lowest on Ryugu’s surface. That movement leaves the higher equator and polar regions relatively bluer and brighter.

Based on this data, the scientists posit that Ryugu was closer to the Sun from 800,000 to 8 million years ago, and that the evidence also suggests that the asteroid is only at most 17 million years old.

To put it mildly, there are great uncertainties to these conclusions.

Hayabusa-2 fires main ion engines for return to Earth

After spending two weeks testing its main ion engines just beyond the gravitational sphere of influence of the asteroid Ryugu, Japanese engineers today initiated full engine operation, beginning the spacecraft’s journey back to Earth.

Hayabusa-2 is expected to return to Earth space in December 2020, where it will release a small capsule containing the two samples it obtained of Ryugu will be released to land on Earth and be recovered. At that point, if Hayabusa-2 is still in good condition it will be available to send to other locations in the solar system.

Hayabusa-2 begins journey back to Earth

The Hayabusa-2 science team has fired up the spacecraft’s ion engine to leave the asteroid Ryugu and began its begins journey back to Earth.

It will take about six days to exit the gravitational sphere of influence of Ryugu. During that time period they will be continually releasing real time images of the asteroid from the spacecraft’s navigation camera, as it slowly gets farther away.

In mid-December they will fire the spacecraft’s main engines for an arrival near Earth in late 2020. At that point the small return capsule holding the samples from Ryugu will separate and land in the Australian desert. Hayabusa-2, still operational, might then be given a new subsequent mission.

Hayabusa-2 to begin return voyage on November 13

In a press conference today the science team for the asteroid probe Hayabusa-2 announced that the spacecraft will begin the first stage of its journey back to Earth tomorrow, using its ion engine to slowly pull away from Ryugu.

That first stage will take a little less than a week. Once the spacecraft gets about 25 miles from Ryugu it will leave its sphere of gravitational influence, when it will then begin its cruise phase back to Earth.

Bennu & Ryugu: Two very old and strange asteroids

Bennu as seen by OSIRIS-REx
Bennu’s equatorial ridge. Click for full image.

This week the science team operating the OSIRIS-REx spacecraft at the asteroid Bennu hosted a joint conference in Tucson, Arizona, with the scientists operating the Hayabusa-2 spacecraft at the asteroid Ryugu. Both gave up-to-date reports on the science so far obtained, as well as outlined upcoming events. I was fortunate enough to attend.

First an overview. Both Bennu and Ryugu are near earth asteroids, with Bennu having an orbit that might even have it hit the Earth in the last quarter of 2100s. Both are very dark, and are rubble piles. Both were thought to be of the carbonaceous chondrite family of asteroids, sometimes referred to as C-type asteroids. This family, making up about 75% of all asteroids, includes a bewildering collection of subtypes (B-types, F-types, G-types, CI, CM, CV, CH, CB, etc), all of which were initially thought to hold a lot of carbon. We now know that only a few of these categories, the CI and CM for example, are carbon rich.

Even so, we actually know very little about these types of asteroids. They are very fragile, so that any that reach the Earth’s surface are not a good selection of what exists. About 90% of the material gets destroyed in the atmosphere, with the remnant generally coming from the innermost core or more robust nodules. We therefore have a biased and limited sample.

It is therefore not surprising that the scientists are finding that neither Bennu nor Ryugu resembles anything else they have ever seen. Both have aspects that resemble certain types of carbonaceous chondrite asteroids, but neither provides a very good fit for anything.
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Hayabusa-2 completes rehearsal for MINERVA-II drop

Hayabusa-2 has successfully completed its rehearsal for its planned drop of its last MINERVA-II bouncer/rover, releasing two reflective targets in order to track how they spiral down to the surface of Ryugu.

Hayabusa 2’s cameras will track the movement of the two navigation aids as they fly in space around Ryugu over the next several days. Scientists expect Ryugu’s tenuous gravity will pull the target markers to the asteroid’s surface within a week.

The release of that last bouncer is now expected in about a month. After spending time obtaining the data from that drop, Hayabusa-2 will then head back to Earth by the end of the year.

Hayabusa-2 dropping orbiting target marker

In preparation for the release and landing of Hayabusa-2’s second MINERVA-II2 tiny rover/bouncer, the spacecraft today began a close-approach to the asteroid Ryugu, where it will release two target markers.

Once released, Hayabusa-2 will back off to observe these markers as they spiral down into Ryugu, landing sometime around September 23.

This operation is a rehearsal for the release and landing of MINERVA-II2, which like the first two bouncers back in September 2018 will bounce along the asteroid’s surface, taking pictures and gathering data.

Hayabusa-2 in safe mode for one day on August 29

Japan’s Hayabusa-2 space probe automatically entered safe mode for one day on August 29, causing engineers to postpone a planned operation set for Sept 5.

Hayabusa2 is equipped with four reaction wheels that are used to control the posture of the spacecraft, and posture control is usually performed using three of these reaction wheels. On August 29, the back-up reaction wheel that has not been used since October last year was tested, and an abnormal value (an increased torque) as detected. The spacecraft therefore autonomously moved into the Safe-Hold state. Details of the cause of the abnormal torque value are currently under investigation. On August 30, restoration steps were taken and the spacecraft returned to normal. However, as the spacecraft moved away from the home position due to entering Safe-Hold, we are currently having to return to the home position. We will return to the home position this weekend.

The attitude of the spacecraft is controlled by three reaction wheels as before. Entering the Safe-Hold state is one of the functions employed to keep the spacecraft safe, which means that procedures have worked normally.

In this case it is very clear that this event actually demonstrated that the spacecraft’s systems are operating properly to prevent it from becoming lost. However, the event also underlined the urgency of getting its samples from the asteroid Ryugu back to Earth.

Results from tiny MASCOT lander on Ryugu

The scientists in charge of the tiny MASCOT lander dropped from Japan’s Hayabusa-2 spacecraft today released the results from the lander’s short seventeen hour observations of the surface of Ryugu.

They found that the asteroid has two different types of rocks (why is a mystery) and practically no dust.

Ralf Jaumann and his team were particularly surprised by the lack of dust: “Ryugu’s entire surface is littered with boulders, but we have not discovered dust anywhere. It should be present, due to the bombardment of the asteroid by micrometeorites over billions of years, and their weathering effect. However, as the asteroid has very low gravity – only one-sixtieth of that experienced on Earth’s surface – the dust has either disappeared into cavities on the asteroid or has escaped into space. This gives an indication of the complex geophysical processes occurring on the surface of this small asteroid.”

They also confirmed that the asteroid is a very fragile rubble pile.

“If Ryugu or another similar asteroid were ever to come dangerously close to Earth and an attempt had to be made to divert it, this would need to be done with great care. In the event that it was impacted with great force, the entire asteroid, weighing approximately half-a-billion tonnes, would break up into numerous fragments. Then, many individual parts weighing several tonnes would impact Earth,” says Jaumann, who is supervising the MASCam experiment, interpreting the observations. The asteroid is very similar to carbonaceous meteorites found on Earth, which date back 4.5 billion years. With an average density of just 1.2 grams per cubic centimetre, Ryugu is only a little ‘heavier’ than water ice. But as the asteroid is made up of numerous pieces of rock of different sizes, this means that much of its volume must be traversed by cavities, which probably makes this diamond-shaped body extremely fragile.

MASCOT was another example of a cubesat demonstrating that these tiny spacecraft can do very sophisticated science.

Japan’s plan for returning Hayabusa-2’s Ryugu samples to Earth

Japan’s today provided an update on what it has done to prepare the location where Hayabusa-2’s samples from the asteroid Ryugu will land on Earth.

The landing site is in the Woomera Prohibited Area (WPA) in the outback of southern Australia. Japan has already signed an agreement with that country for the recovery, as well as done preliminary surface work

The recovery site is an Australian Government prohibited area and is not accessible to the public. As part of the preparatory work, a field survey of the proposed recovery site in the WPA was conducted with permission from the Australian Government. This preparatory work confirmed the suitability of both the proposed recovery site and the candidate site for the antenna station that will search for the capsule.

The landing of the recovery capsule is now scheduled for late in 2020.

Hayabusa-2: Carbon-rich asteroids too delicate to reach Earth surface

New data from Hayabusa-2 has confirmed the long-held suspicions of astronomers that the reason they find so few fragments of C-class asteroids, such as Ryugu, on Earth is because they are too delicate to reach the Earth’s surface.

Ryugu and other asteroids of the common ‘C-class’ [chondritic] consist of more porous material than was previously thought. Small fragments of their material are therefore too fragile to survive entry into the atmosphere in the event of a collision with Earth.

…Until now, only a few chondritic meteorites found on Earth have been identified as fragments of C-type asteroids, which are very common in the Solar System (‘C’ is the chemical symbol for the element carbon). …”We can now confirm that fragments of these asteroids are very likely to break up further when they enter Earth’s atmosphere, and then usually burn up completely. This means that only the largest fragments reach the Earth’s surface,” explains Grott. “That is why meteorites from this type of asteroid are so rarely found on Earth.”

The good news is that, because of this, Earth’s atmosphere offers increased protection from C-type asteroids, which account for 75 percent of all asteroids. …However, further research is necessary to determine the maximum asteroid size for which this atmospheric protection is effective.

It is likely that even the largest rubble-pile C-asteroids will not pose much risk. Even if some pieces reach the Earth’s surface they are probably going to be small and unable to do much harm.

Hayabusa-2’s second touchdown sample grab

Hayabusa touchdown sequence

The Hayabusa-2 science team yesterday released a series of close-up images taken just as the spacecraft touched down and then backed off from the surface of Ryugu.

I have cropped and annotated that sequence and placed all three images side-by-side above. The red arrows in the first two images highlight similar shadows in both pictures, with the appearance of dust visible in the lower center of the middle touchdown picture. I have not marked any comparable surface features in the third image because the uplift of material makes it too difficult.

That uplift however is exactly what the Hayabusa-2 science team needs, as it is some of this material that has hopefully been captured. Their fear was that this uplift posed a risk to the spacecraft itself, but they took precautions to minimize the risk and it appears that these precautions have worked.

We now must wait until the samples come back to Earth in December 2020 to see exactly what they caught.

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