Astro Bob: Scientists love 'lumps of coal' in their Christmas stockings

The Japanese Hayabusa-2 asteroid mission returns a bounty of material from a potentially hazardous asteroid, while China's scientists begin examination of a fresh batch of moon rocks.

On December 21, sample catcher chambers in the Hayabusa2 landing capsule were opened and moved to the collection containers in the photo. Each black fragment is a piece of Ryugu, a potentially hazardous asteroid the orbits the sun near the Earth. The arrow points to a possible piece of aluminum from the sample collector itself that somehow wound up inside the container. 5mm = about one-fifth of an inch. The largest fragments are about 0.4 inch long. (Japan Aerospace Exploration Agency — JAXA)

Traditionally, naughty girls and boys get a lump of coal in their Christmas stockings, but the myriad black shards and pebbles returned from the Hayabusa-2 mission are just what Japanese scientists wished for on this special day. They needed a minimum of 0.1 grams (.004 ounce) for scientific analysis. Happily, the spacecraft collected much more — about 5.4 grams, equal to a little more than a teaspoon of sugar. That doesn't sound like much, but with modern day instruments capable of analyzing minute amounts of material, that's almost a bushel basket full.

Hayabusa-2 arrived at Ryugu, a near-Earth asteroid just 0.6 miles (1 km) across, in June 2018. After measuring, photographing and sampling the object, it left for Earth and returned the material in a capsule that landed in the Australian Outback on Dec. 5, 2020.

Meteorite CM2 Aguas Zarcas.JPG
Here are two small pieces of the Aguas Zarcas carbonaceous chondrite meteorite that fell in Costa Rica on April 23, 2019. The fragment on the left is coated in black fusion crust; the other is a slice that reveals the meteorite's interior. (Bob King)

To my eye, the crumbles look just like black, carbon-and-water-rich meteorites that fall to Earth called carbonaceous chondrites (kar-bun-AY-shuss KON-drites) with a difference: they lack the thin layer of black fusion crust that coats incoming meteoroids when friction with the atmosphere melts their outer layers. And that's exactly what makes this material so special — it hasn't been tainted by the Earth, a planet always trying to get its fingers into everything.


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Asteroid 162173 Ryugu is shaped a little like a spinning top and measures just 0.6 miles across. This pair of images shows its two hemispheres. (JAXA)

It's not surprising that the shards resemble carbon-rich meteorites as studies of sunlight reflected from Ryugu reveal that it's composed of similar material. If so, those black rocks in the canister could be rich with organic compounds including amino acids, the building blocks of proteins, also found in some carbonaceous meteorites.

Although the asteroid looks relatively bright against the background of space, the fragments look black under normal lighting on Earth. That's because Ryugu is exceptionally dark, reflecting slightly less than 4% of the sunlight it receives. The moon, much of which is as black as charcoal, shines three times brighter.

Ryugu orbit HORIZONS.jpg
As Ryugu orbits the sun it occasionally passes near the Earth. The name is Japanese for "dragon palace" and refers to a mythological place in Japanese folklore. The object is a potentially hazardous asteroid (PHA) with a remote chance of striking our planet in the distant future. As of September 2020 we know of 2,116 PHAs. (JPL-HORIZONS)

I'll post more news about what scientists discover in these treasured bits in the coming weeks. In a related story, the Chinese Chang'e 5 lunar sample return mission successfully recovered 3.8 pounds (1,731 grams) of rocks and dust, the first lunar materials returned to Earth in over 40 years. The lander drilled and collected rocks from from a never-before-sampled location near a relatively young volcanic feature called Mt. Rümker (Mons Rümker) in the moon's northern hemisphere. The return capsule landed in Inner Mongolia on Dec. 17.


In addition to scientific study in China, Wu Yanhua, deputy director of the China National Space Administration, said that some of the material would go on public display in China's National Museum and shared with scientists around the world … with the possible exception of NASA. Why? A 2011 Act of Congress called the Wolf Amendment restricts the agency from cooperating with China in space-related matters due to the risk of espionage.

NASA did cooperate with China during its 2019 Chang'e 4 mission to the lunar farside but had to get special Congressional approval to do so. Let's hope they'll ask for a pass again. Sharing data is at the heart of good science, and NASA has some of the best facilities and smartest people on the planet, not to mention a long history of studying and sharing its own moon rocks from the Apollo missions.

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Two new sunspot groups are easily visible in this low-power telescope view even with strong atmospheric turbulence (look at the sun's ruffled edge) on Christmas Day. (Bob King)

In a completely unrelated bit of news, two new groups of sunspots speckle the sun this week. Any small telescope equipped with a safe solar filter will bring them into view. So far, these active regions have been on the quiet side with no significant flares. But who knows? We'll be watching.

"Astro" Bob King is a freelance writer for the Duluth News Tribune. Read more of his work at .

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