矢野 創

Researchers have proposed that the building blocks of life may have originated in a turbulent region near Jupiter, not exclusively deep out in space.

小惑星から直接採集したサンプルは、地球の生物に汚染されていないこと、大量に採集できないことから、最も貴重な科学サンプルです。このためサンプルの取り扱い時には、汚染に対して細心の注意が図られます。 インペリアル・カレッジ・ロンドンのMatthew J. Genge氏を筆頭著者とする国際研究チームは、宇宙航空研究開発機構（JAXA）の小惑星探査機「はやぶさ2」が採集した小惑星「リュウグウ」のサンプルを観察したところ、生物の細胞が付着していることを確認しました。 もちろんこれは地球外生物ではなく、地球のどこにでもいるありふれた細菌であることがすぐに明らかとなっています。また、細菌の成長度合いからすると、研究を行ったインペリアル・カレッジ・ロンドンでの取り扱い中に細菌が付着した可能性が高いと考えられます。 今回の結果は、小惑星のサンプルのような貴重品を取り扱う際には、普段している以上の汚染対策を行うべきであることを強調しています。一方で逆説的ではあるものの、JAXAにおけるサンプル取り扱い時の汚染対策がいかに厳重かつ適切であったかを示しています。さらに今回の結果は、小惑星サンプルの取り扱い方法だけでなく、月や火星へ向かう探査機の汚染対策や、隕石に含まれる生物のような構造の解釈など、様々な方面にも影響を与えそうです。

Material from asteroid Ryugu riddled with earthly microbes provides a cautionary tale for scientists seeking signs of alien life

探査機「はやぶさ２」が持ち帰った小惑星「りゅうぐう」の砂粒から、地球で混入したとみられる微生物が見つかったと、英大学インペリアル・カレッジ・ロンドンなどの研究チームが１日までに、国際隕石（いんせき）学会誌に発表した。 「りゅうぐう」砂に塩の結晶 試料分析で発見―京都大など オーストラリアでの試料カプセル回収から宇宙航空研究開発機構（ＪＡＸＡ）による初期分析までは外気に触れない環境が維持されていたことなどから、研究チームは微生物が地球外由来ではなく、英国での分析中に混入したと判断した。 研究チームの矢野創ＪＡＸＡ助教は「火星や、木星の衛星などから生命の痕跡を探そうとするサンプルリターン計画が注目されているが、汚染に気を付けて分析しないといけないことが改めて示された」と将来の探査に向けた課題を指摘した。 分析した砂粒は、研究チームがＪＡＸＡから受け取った後、２０２２年７月に窒素を封入した密閉コンテナで英国に移送。同年１０月１４日、ロンドン自然史博物館の施設でＸ線ＣＴ（コンピューター断層撮影）のために取り出した。 この時のＣＴ画像に微生物は映っていなかったが、１１月１１日の電子顕微鏡撮影で、筒状や細い糸状の微生物とみられるものが１１個見つかった。同月３０日の撮影では１４７個に増えていたが、２３年１月には３６個に減少。同２月に砂粒の表面を研磨した後は、見つからなくなった。 研究チームは、形状などから「バチルス属」など地球上で一般的な微生物と推定。ＣＴ撮影以降に空気中から付着し、砂粒に含まれる有機物を栄養に増殖し、その後利用できる有機物がなくなって減少したと判断した。 英国到着後の作業は、宇宙由来の物質の分析や保管方法として一般的なものだったといい、矢野助教は「本気で生命の痕跡を調べるのであれば、地球の大気に少しでも触れては駄目だということ。生命探査を目指すサンプルリターンの難しさがまた一つ証明された」と話した。

Asteroid Ryugu Sample Was 'Rapidly Colonised' By Earth Bacteria: StudyThe research highlights how successful micro-organisms are at colonisation, even for extraterrestrial materials.

Scientists 'found microorganisms within the asteroid sample shortly after it was exposed to Earth’s environment.'

"The fact that terrestrial microbes are the Earth's best colonizers means we can never completely discount terrestrial contamination."

The unexpected discovery of microbial life in a piece of rock from an asteroid shows how hard it is to avoid contaminating samples brought back to Earth

Microorganisms on a sample of asteroid are clearly terrestrial — despite strict protocols to avoid contamination. Be wary of claims of alien life in samples from space, say researchers who found traces of Earthly bacteria in a particle of rock retrieved from the asteroid Ryugu. Matthew Genge at Imperial College London and his colleagues analysed the particle, brought to Earth by the Hayabusa2 mission in 2020. To minimize exposure to Earth’s environment, the sample had been kept in dry and sterile conditions since its arrival. A week after embedding the particle in resin to prepare it for study, researchers imaged the sample and observed 11 microorganisms with cylindrical shapes resembling those of the bacterium Bacillus. The number grew to 147 after three weeks, before declining over the next six weeks. The pattern suggests the asteroid fragment was probably contaminated during sample preparation, say the authors. The readiness with which the bacteria colonized the particle, despite precautions, suggests that researchers should be sceptical of future claims of extraterrestrial life in such samples, the authors note. That home-grown bacteria can feed on organic asteroid matter suggests that outbound missions also need strict controls to protect extraterrestrial environments from contamination, they add.

Cracks running through samples of asteroid Ryugu were probably formed by the repeated thawing and freezing of water inside it, which could have helped asteroids like this carry the building blocks of life to early Earth

Imperial researchers have found that, 4.5 billion years ago, ice modified asteroids in a way that may have led to the beginning of life on Earth.

“あまのじゃく”なリーダーがＮＡＳＡに「星のカケラを持ち帰る」と啖呵（たんか）を切ったことから、人類初の「サンプルリターン」計画は始まった。カギを握ったのは、“ごくつぶし”と言われながらも最新エンジンを研究していた男。宇宙ではトラブルが続出。当初４年計画だった航海は７年に延びた。「はやぶさ」を地球に帰還させるわずかな可能性に、研究者たちは英知の限りを尽くして挑んだ。３億キロのかなたの奇跡の物語。

“宇宙活動”の現在と未来を論じる講演会が来週（2018年11月）24日（土）に日吉キャンパス内で開かれます。慶應義塾高校（慶應塾高）の開設70年事業として、「深海からNew Space そして深宇宙～より身近に、そして、遠くへ」と題して行われます。

https://gendai.media/articles/-/54587?page=2

「あなたの手で、星の王子様のふるさとへ探査機を送り出しませんか？ 」 そんな呼びかけをネット上に発し、期間限定 e グループとして2000年5月に船出した MEF（小天体探査フォーラム）。今も脈々と続くこの有志団体の歴史の中で、間もなく深宇宙航海に旅立つ探査機「はやぶさ2」の DNA は紡がれた。そのことを再確認するために、今こそ改めて「MEF レポート：ポストはやぶさ時代の小天体探査（改訂版）」（小天体探査フォーラム(MEF)編、2004年、全 237 ページ）」をひも解いてみたい。

https://ascii.jp/featuredarticles/530686/

But is Japan's Hayabusa capsule carrying any precious asteroid dust? Yesterday in the south central Australian village of Woomera, Japanese scientists, with US and Australian colleagues, celebrated news from their Hayabusa spacecraft — the first round-trip space mission to an asteroid. Successful manoeuvres that day had put the spacecraft on course to parachute its recovery capsule into the nearby desert on 13 June. Anticipation will continue to build until the capsule's lid is opened, offering, they hope, the first peek at asteroid dust. Scientists anticipate that such samples will provide greater knowledge of these 'little planets', shedding light on the beginnings of the Solar System, the origins of life on Earth (see 'Asteroid ice hints at rocky start to life on Earth') and the connection between asteroids and the tens of thousands of meteorites that have been found on Earth. "It could establish a bridge for the first time," says Michael Zolensky, a NASA scientist who will analyse some of the Hayabusa samples. The original aim of Hayabusa was as a technical mission to test various engineering technologies, such as ion-thrust engines and autonomous navigation systems, needed for landing on an asteroid and returning to Earth. The spacecraft, launched in May 2003, landed on the 535-metre-long Itokawa asteroid twice in November 2005. The mission is lucky to get this far, says Hajime Yano, a Hayabusa project scientist with the Japan Aerospace Exploration Agency (JAXA). After the spacecraft landed on Itokawa a second and final time, a massive fuel leak resulted in loss of communication for several months. Hayabusa's engines also experienced a range of problems, and its return was uncertain until 8 June, when its faltering thrusters completed the last necessary trajectory correction. "It's like a critical patient who can't walk well," says Yano. "Up until yesterday, anything could have happened." Mission accomplished Although three years behind schedule, the mission has achieved its major goals, and has already yielded scientific data about Itokawa's dimensions and composition, which will provide a benchmark for future asteroid studies. The remaining mission goals are retrieving the sample-return capsule from the desert and analysing any samples within it. The capsule is a disk-shaped aluminium container about 40 centimetres in diameter, and is scheduled to separate from the craft on 13 June before entering Earth's atmosphere. "From their perspective, it's all gravy," says Scott Sandford, another NASA scientist working on the project. "Everything we're getting now is a bonus, but to me it's the most interesting part." From their perspective, it's all gravy. , The incoming capsule has a radio beacon to signal its location, and infrared-detection devices on helicopters will also be used to find it. Even if these fail, monitoring stations will track the burning wreckage of Hayabusa through the atmosphere as a guide to the trajectory of the nearby capsule. JAXA scientists will retrieve the capsule on 14 June, and by the end of the week, they hope to have it back in their laboratory in Sagamihara, just south of Tokyo. There they will first take X-ray images to estimate the amount of dust picked up — if any. High hopes Zolensky says they were originally hoping to have "spoonfuls, several grams of sample", made up of "chips like peanut-size grains". But sample collection didn't go as planned. Pellets designed to hit Itokawa to dislodge loose fragments seem not to have fired. "It's very likely we won't be able to see anything with the naked eye," says Makoto Yoshikawa, also a Hayabusa project scientist at JAXA. Still, the scientists have high hopes. A hard impact on Hayabusa's first landing attempt on the asteroid is likely to have kicked up dust, says Yoshikawa. Hayabusa sat on the surface for 30 minutes after that. Zolensky agrees: "Just the fact that it landed should cover it in dust. The astronauts on the Moon got covered with dust just walking around. The mission team might not get grams, but they'll have something. With today's technologies, even microbe-sized particles should be enough." On the basis of the X-ray results, the researchers will decide when and how to open the lid and distribute the contents between analysis and storage. Any dust that is found will be analysed over the next six months as scientists look at oxygen isotopes, helium content, water traces, and other clues that might provide insight into Itokawa's history. "We want to look at its elemental composition and structure," says Yoshikawa. "When this asteroid was born, what kind of matter was around? This will tell us about Earth and the Solar System."