彗星、内部はすかすか 世界初着陸機の成果特集
2015年7月31日 05時21分 中日新聞
着陸時に予定外のバウンドをしたことで、表面の新たなデータも得られた。３１日付の米サイエンス誌が特集し、研究チームの論文７本を掲載した。
太陽系の生命の起源との関連が注目される水や有機化合物が１６種類存在することを確認、うち４種類は彗星で初めて見つかった。
フィラエ(Philae) が着陸したチュリュモフ・ゲラシメンコ彗星は８月１３日の太陽最接近を控え、ガスを噴出するなど活動を活発化させており、今後も新たな発見が期待される。
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彗星着陸時、有機物検出＝欧州の探査機フィラエ
時事通信 7月31日(金)5時30分配信 headlines.yahoo.co.jp
欧州宇宙機関（ESA）の探査機フィラエが昨年11月にチュリュモフ・ゲラシメンコ彗星に着陸した際、さまざまな有機化合物を検出したと、ドイツのマックスプランク研究所などの欧米研究チームが31日付の米科学誌サイエンスに発表した。
この中には過去の彗星探査で未検出のアセトンやアセトアミドなど4種類の有機化合物も含まれていた。
生物を構成するたんぱく質の部品であるアミノ酸は確認できなかったが、生命の起源を探る研究に役立つと期待される。
フィラエは親機ロゼッタから分離されて彗星に着陸した際、地面に固定する装置が作動しなかったため、大小のバウンドを経て約2時間後に約1キロ離れた所に落ち着いた。
着陸の衝撃で地面の粒子が舞い上がり、フィラエに搭載された分析装置内に自然に入ったため、よく分析できた。
米航空宇宙局（NASA）の探査機スターダストが2004年にビルト第2彗星に接近、採取したちりからは、地球に回収された後の分析でアミノ酸の一種グリシンが検出されたと発表されている。
Surprising Comet Discoveries by Rosetta's Philae Lander Unveiled
by Mike Wall, Space.com Senior Writer | July 30, 2015 02:01pm ET
space.com/30100-comet-landing-discoveries-rosetta-philae-lander
Philae's landing points on Comet 67P/Churyumov-Gerasimenko on Nov. 12, 2014.
Credit: ESA/ROSETTA/NAVCAM/SONC/DLR
Credit: ESA/ROSETTA/NAVCAM/SONC/DLR
The structure, composition and evolutionary history of comets are starting to come into focus, thanks to observations beamed home by the first probe ever to land on one of these icy objects.
On Nov. 12, 2014, the European Space Agency's Philae lander detached from its Rosetta mother ship, which had arrived in orbit around Comet 67P/Churyumov-Gerasimenko three months earlier, and spiraled down toward the icy wanderer's surface.
The historic touchdown didn't go exactly as planned, however. Philae's anchoring harpoons failed to fire, and the 220-lb. (100 kilograms) lander bounced off 67P's surface, clipped a crater rim and then bounced a second time before finally coming to rest nearly two hours after first making contact with the comet's surface.
spaceflightnow.com/2014/11/18/philae-finds-comet-harbors-organics/
Philae lander found a surface as hard as ice and organic molecules after it bounced to a stop on a comet last week.
Scientists looking over the spoils from the plucky little Philae probe released some of the first results from the mission Monday after a hectic week of descent preparations, a dramatic landing that included three touchdowns, and more than 60 hours of data gathering.
“We have collected a great deal of valuable data, which could only have been acquired through direct contact with the comet,”
said Ekkehard Kuhrt, scientific director for the Philae mission at DLR — the German space agency.
“Together with the measurements performed by the Rosetta orbiter, we are well on our way to achieving a greater understanding of comets. Their surface properties appear to be quite different than was previously thought.”
After coming to rest on its side, Philae continued transmitting data intermittently when in range of Rosetta, the European-built orbiter that deployed the refrigerator-sized lander for its descent Wednesday.
Before its battery died, Philae unfurled an instrument boom to study the comet’s surface properties. The MUPUS instrument was designed to hammer into the nucleus about 1.5 meters (about 5 feet) from the lander, and data show the system worked as planned despite Philae’s precarious position lodged against a rocky face at an angle with one leg pointing into space.
“Although the power of the hammer was gradually increased, we were not able to go deep into the surface,”
said Tilman Spohn, head of the MUPUS instrument on Philae. “We have acquired a wealth of data, which we must now analyze.”
According to a DLR press release, the MUPUS team estimates the outer skin of the comet’s nucleus — at least where Philae settled after its bouncy landing — is as hard as ice.
nytimes.com/interactive/2014/11/12/science/space/rosetta-philae-comet-landing
“With MUPUS it has been possible to directly study the strength of a comet’s surface for the first time — and 67P/Churyumov-Gerasimenko proved to be a ‘tough nut to crack,'”
DLR said in a statement Monday.
The MUPUS sensors were supposed to measure the comet’s t![イメージ 7]()
emperature, the mechanical properties of its surface, and its thermal conductivity.
Only thermal and acceleration sensors in Philae’s two harpoons were not used, DLR said, because the anchoring system was not deployed during landing.
Data collected by P![イメージ 10]()
hilae’s SESAME experiment suite support MUPUS results indicating the comet’s unexpected toughness. Early findings also show a low level of cometary activity at the probe’s landing site and a large amount of water ice under the lander, according to DLR.
“The strength of the ice founds under a layer of dust on the first landing site is surprisingly high,”
said Klaus Seidensticker from the DLR Institute of Planetary Research, lead scientist on the SESAME instrument package, which was expected to study the comet’s composition and electrical, structural and mechanical characteristics.
nytimes.com/interactive/2014/11/12/science/space/rosetta-philae-comet-landing
While officials said Monday it was clear the drill worked, they could not say whether it gathered samples and deposited them in the lander’s instruments.
One of Philae’s sample analysis sensors — named COSAC — did collect data in “sniff” mode and detected organic molecules, presumably outgassing just above the comet’s surface.
Philae’s descent imaging camera was also switched back on and took up-close images of the comet’s nucleus at the lander’s final resting site. The down-facing camera also recorded imagery of Philae’s descent to the craft’s initial landing site before it rebounded to two more touchdowns.
Scientists were also able to use Philae in conjunction with Rosetta to study the comet’s internal structure, DLR said.
“To achieve this, the lander and orbiter were on different sides of the comet and worked together to analyse the comet nucleus by passing radio signals through it and creating a three-dimensional profile of the core,”
the DLR statement said.
Scientists are hopeful Philae will recharge its batteries in the coming weeks and months, allowing for the mission to resume as the comet nears the sun.