NASAの探査機ドーン セレス(ケレス)とベスタの最新画像と全文翻訳



time 2017/02/17


オリジナル記事:Dawn Discovers Evidence for Organic Material on Ceres

NASA’s Dawn mission has found evidence for organic material on Ceres, a dwarf planet and the largest body in the main asteroid belt between Mars and Jupiter. Scientists using the spacecraft’s visible and infrared mapping spectrometer (VIR) detected the material in and around a northern-hemisphere crater called Ernutet. Organic molecules are interesting to scientists because they are necessary, though not sufficient, components of life on Earth.


The discovery adds to the growing list of bodies in the solar system where organics have been found. Organic compounds have been found in certain meteorites as well as inferred from telescopic observations of several asteroids. Ceres shares many commonalities with meteorites rich in water and organics — in particular, a meteorite group called carbonaceous chondrites. This discovery further strengthens the connection between Ceres, these meteorites and their parent bodies.


“This is the first clear detection of organic molecules from orbit on a main belt body,” said Maria Cristina De Sanctis, lead author of the study, based at the National Institute of Astrophysics, Rome. The discovery is reported in the journal Science.


Data presented in the Science paper support the idea that the organic materials are native to Ceres. The carbonates and clays previously identified on Ceres provide evidence for chemical activity in the presence of water and heat. This raises the possibility that the organics were similarly processed in a warm water-rich environment.


This enhanced color composite image, made with data from the framing camera aboard NASA’s Dawn spacecraft, shows the area around Ernutet Crater. The bright red portions appear redder with respect to the rest of Ceres.


Significance of organics

The organics discovery adds to Ceres’ attributes associated with ingredients and conditions for life in the distant past. Previous studies have found hydrated minerals, carbonates, water ice, and ammoniated clays that must have been altered by water. Salts and sodium carbonate, such as those found in the bright areas of Occator Crater, are also thought to have been carried to the surface by liquid.


“This discovery adds to our understanding of the possible origins of water and organics on Earth,” said Julie Castillo-Rogez, Dawn project scientist based at NASA’s Jet Propulsion Laboratory in Pasadena, California.


This enhanced color composite image from Dawn’s visible and infrared mapping spectrometer shows the area around Ernutet Crater on Ceres. The instrument detected the evidence of organic materials in this area, as reported in a 2017 study in the journal Science. In this view, areas that appear pink with respect to the background appear to be rich in organics, and green areas are where organic material appears to be less abundant.Light with a wavelength of 2000 nanometers is shown in blue, 3400 nanometers is shown in green and 1700 nanometers is shown in red.

ドーンの可視赤外マッピングスペクトロメータの色を強調したカラー画像は、セレスのレネネトクレーター周辺を示しています。 2017年のサイエンス誌の研究論文で報告されているように、この地域で有機物の証拠が検出されました。この画像では、背景に対してピンク色に見える領域は有機物が豊富で、緑色の領域は有機物が豊富でないとされる領域です。2000ナノメートルの波長の光は青色で表示され、3400ナノメートルが緑色と1700ナノメートルが赤で示されています。

Where are the organics?

The VIR instrument was able to detect and map the locations of this material because of its special signature in near-infrared light.


The organic materials on Ceres are mainly located in an area covering approximately 400 square miles (about 1,000 square kilometers). The signature of organics is very clear on the floor of Ernutet Crater, on its southern rim and in an area just outside the crater to the southwest. Another large area with well-defined signatures is found across the northwest part of the crater rim and ejecta. There are other smaller organic-rich areas several miles (kilometers) west and east of the crater. Organics also were found in a very small area in Inamahari Crater, about 250 miles (400 kilometers) away from Ernutet.


In enhanced visible color images from Dawn’s framing camera, the organic material is associated with areas that appear redder with respect to the rest of Ceres. The distinct nature of these regions stands out even in low-resolution image data from the visible and infrared mapping spectrometer.


“We’re still working on understanding the geological context for these materials,” said study co-author Carle Pieters, professor of geological sciences at Brown University, Providence, Rhode Island.


Ernutet Crater measures about 32 miles (52 kilometers) in diameter and is located in the northern hemisphere of Ceres.


Next steps for Dawn

Having completed nearly two years of observations in orbit at Ceres, Dawn is now in a highly elliptical orbit at Ceres, going from an altitude of 4,670 miles (7,520 kilometers) up to almost 5,810 miles (9,350 kilometers). On Feb. 23, it will make its way to a new altitude of around 12,400 miles (20,000 kilometers), about the height of GPS satellites above Earth, and to a different orbital plane. This will put Dawn in a position to study Ceres in a new geometry. In late spring, Dawn will view Ceres with the sun directly behind the spacecraft, such that Ceres will appear brighter than before, and perhaps reveal more clues about its nature.

セレスの軌道上からほぼ2年間の観測を完了したドーンは、現在セレスの楕円軌道上にあり、高度4,670マイル(7,520キロメートル)から5,810マイル(9,350キロメートル)に位置しています。 2月23日には、高度約12,400マイル(20,000キロメートル)の新しい軌道に移りますが、地球でいえばGPS衛星の高度と同じくらいになります。これはドーンがセレスの新たな地殻研究することができるようになります。春の終わりには、ドーンはセレスを真後ろに太陽光のもとに直接見ることになります。その際はセレスは以前よりも明るく見え、おそらくいろいろな謎のさらなる手掛かりを明らかにするでしょう。

The Dawn mission is managed by JPL for NASA’s Science Mission Directorate in Washington. Dawn is a project of the directorate’s Discovery Program, managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team.

For a complete list of mission participants, visit:
More information about Dawn is available at the following sites:

Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, CA

Last Updated: Feb. 17, 2017
Editor: Tony Greicius




⇒ サイエンスジャーナル誌に発表したので詳しくはそちらで。


⇒ いろいろな発見がありそう。

ちなみに記事中の”Ernutet Crater”ですがErnutetとはエルヌテトではなく汎用的なレネネトと記載しています。

レネネト – Wikipediaレネネト

レネネト(Renenet。レネヌテト (Renenutet) または エルヌテト(Ernutet) とも)は、エジプト神話に登場する、人間の赤ん坊に乳を与えて養育する乳母の女神である。レネネトを描く際は、ファラオや時には死者にその乳を与える様子が描かれた。


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