They are formed when various types of dust and small grains that were present in the early solar system accreted to form primitive asteroids. They are the most common type of meteorite that falls to Earth: they are about 85 or 86 percent of all meteorites.[2] Their study gives clues about the origin and age of the Solar System, the synthesis of organic compounds, the origin of life or the presence of water on Earth. Chondrites can be differentiated from iron meteorites by their low iron and nickel content. Carbonaceous chondrites In 2021, a meteorite crashed on the Gloucestershire town of Winchcombe. It contained water that was a near-perfect match for that on Earth. The meteorite was picked up soon after it landed.[3] This is a suggested source for the water on Earth. Achondrites About 8 percent of meteorites show signs of melting and recrystallizing. They look rather like basalt or granite. Iron meteorites Iron meteorites are meteorites made of an iron–nickel alloy. They are about 6 percent of all meteorites. A meteor, known colloquially as a shooting star, is a glowing streak of a small body (usually meteoroid) going through Earth's atmosphere, after being heated to incandescence by collisions with air molecules in the upper atmosphere, creating a streak of light via its rapid motion and sometimes also by shedding glowing material in its wake. Meteors typically occur in the mesosphere at altitudes from 76–100 kilometres (47–62 miles). The root word meteor comes from the Greek μετεωρίτης (meteōrítēs), meaning "high in the air". Millions of meteors occur in Earth's atmosphere daily. Most meteoroids that cause meteors are about the size of a grain of sand, i.e. they are usually 1 mm (1⁄25 in) or smaller. Meteoroid sizes can be calculated from their mass and density which, in turn, can be estimated from the observed meteor trajectory in the upper atmosphere. Meteors may occur in showers, which arise when Earth passes through a stream of debris left by a comet, or as "random" or "sporadic" meteors, not associated with a specific stream of space debris. A number of specific meteors have been observed, largely by members of the public and largely by accident, but with enough detail that orbits of the meteoroids producing the meteors have been calculated. The atmospheric velocities of meteors result from the movement of Earth around the Sun at about 30 km/s (67,000 mph; 110,000 km/h), the orbital speeds of meteoroids, and the gravity well of Earth. Meteors become visible between about 75 to 120 km (47 to 75 mi) above Earth. They usually disintegrate at altitudes of 50 to 95 km (31 to 59 mi). Meteors have roughly a fifty percent chance of a daylight (or near daylight) collision with Earth. Most meteors are, however, observed at night, when darkness allows fainter objects to be recognized. For bodies with a size scale larger than 10 cm (4 in) to several meters meteor visibility is due to the atmospheric ram pressure (not friction) that heats the meteoroid so that it glows and creates a shining trail of gases and melted meteoroid particles. The gases include vaporised meteoroid material and atmospheric gases that heat up when the meteoroid passes through the atmosphere. Most meteors glow for about a second. The entry of meteoroids into Earth's atmosphere produces three main effects: ionization of atmospheric molecules, dust that the meteoroid sheds, and the sound of passage. During the entry of a meteoroid or asteroid into the upper atmosphere, an ionization trail is created, where the air molecules are ionized by the passage of the meteor. Such ionization trails can last up to 45 minutes at a time. Small, sand-grain sized meteoroids are entering the atmosphere constantly, essentially every few seconds in any given region of the atmosphere, and thus ionization trails can be found in the upper atmosphere more or less continuously. When radio waves are bounced off these trails, it is called meteor burst communications. Meteor radars can A meteor shower is the result of an interaction between a planet, such as Earth, and streams of debris from a comet or other source. The passage of Earth through cosmic debris from comets and other sources is a recurring event in many cases. Comets can produce debris by water vapor drag, as demonstrated by Fred Whipple in 1951, and by breakup. Each time a comet swings by the Sun in its orbit, some of its ice vaporizes and a certain amount of meteoroids are shed. The meteoroids spread out along the entire orbit of the comet to form a meteoroid stream, also known as a "dust trail" (as opposed to a comet's "dust tail" caused by the very small particles that are quickly blown away by solar radiation pressure). The frequency of fireball sightings increases by about 10–30% during the weeks of vernal equinox. Even meteorite falls are more common during the northern hemisphere's spring season. Although this phenomenon has been known for quite some time, the reason behind the anomaly is not fully understood by scientists. Some researchers attribute this to an intrinsic variation in the meteoroid population along Earth's orbit, with a peak in big fireball-producing debris around spring and early summer. Others have pointed out that during this period the ecliptic is (in the northern hemisphere) high in the sky in the late afternoon and early evening. This means that fireball radiants with an asteroidal source are high in the sky (facilitating relatively high rates) at the moment the meteoroids "catch up" with Earth, coming from behind going in the same direction as Earth. This causes relatively low relative speeds and from this low entry speeds, which facilitates survival of meteorites. It also generates high fireball rates in the early evening, increasing chances of eyewitness reports. This explains a part, but perhaps not all of the seasonal variation. Research is in progress for mapping the orbits of the meteors to gain a better understanding of the phenomenon.

ABSTRACT Recent detection of exoplanets with Earth-like insolation attracts growing interest in how common Earth-like aqua planets are beyond the Solar system. While terrestrial planets are often assumed to capture icy or water-rich planetesimals, a primordial atmosphere of nebular origin itself can produce water through oxidation of the atmospheric hydrogen with oxidizing minerals from incoming planetesimals or the magma ocean. Thermodynamically, normal oxygen buffers produce water comparable in mole number equal to or more than hydrogen. Thus, the primordial atmosphere would likely be highly Formation of aqua planets with water of nebular origin: effects of water enrichment on the structure and mass of captured atmospheres of terrestrial planets | CiNii Research 検索 タイトル 人物/団体名 著者ID/研究者番号 所属機関 ISSN DOI 期間 〜 本文リンク 本文リンクあり データソース JaLC IRDB Crossref DataCite NDLサーチ NDLデジコレ（旧NII-ELS） RUDA JDCat NINJAL CiNii Articles CiNii Books NACSIS-CAT/ILL DBpedia KAKEN e-Rad Integbio PubMed LSDB Archive 極地研ADS 極地研学術DB OpenAIRE 公共データカタログ すべて 研究データ 論文 本 博士論文 プロジェクト 人物 > 人物検索機能について 詳細検索 閉じる CiNii Researchナレッジグラフ検索機能（試行版）をCiNii Labsにて公開しました 「研究データ」「根拠データ」の収録について CiNii Books機能統合対応の追加実施をいたしました Formation of aqua planets with water of nebular origin: effects of water enrichment on the structure and mass of captured atmospheres of terrestrial planets DOI DOI PDF PDF 被引用文献8件 参考文献62件 オープンアクセス Tadahiro Kimura Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan Masahiro Ikoma Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan 書誌事項 公開日 2020-06-22 資源種別 journal article 権利情報 https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model DOI 10.1093/mnras/staa1778 10.48550/arxiv.2006.09068 公開者 Oxford University Press (OUP) この論文をさがす CiNii Books 説明 <jats:title>ABSTRACT</jats:title><jats:p>Recent detection of exoplanets with Earth-like insolation attracts growing interest in how common Earth-like aqua planets are beyond the Solar system. While terrestrial planets are often assumed to capture icy or water-rich planetesimals, a primordial atmosphere of nebular origin itself can produce water through oxidation of the atmospheric hydrogen with oxidizing minerals from incoming planetesimals or the magma ocean. Thermodynamically, normal oxygen buffers produce water comparable in mole number equal to or more than hydrogen. Thus, the primordial atmosphere would likely be highly enriched with water vapour; however, the primordial atmospheres have been always assumed to have the solar abundances. Here we integrate the 1D structure of such an enriched atmosphere of sub-Earths embedded in a protoplanetary disc around an M dwarf of 0.3$\, \mathrm{M}_\odot$ and investigate the effects of water enrichment on the atmospheric properties with focus on water amount. We find that the well-mixed highly enriched atmosphere is more massive by a few orders of magnitude than the solar-abundance atmosphere, and that even a Mars-mass planet can obtain water comparable to the present Earth’s oceans. Although close-in Mars-mass planets likely lose the captured water via disc dispersal and photoevaporation, these results suggest that there are more sub-Earths with Earth-like water contents than previously predicted. How much water terrestrial planets really obtain and retain against subsequent loss, however, depends on efficiencies of water production, mixing in the atmosphere and magma ocean, and photoevaporation, detailed investigation for which should be made in the future.</jats:p> 収録刊行物 Monthly Notices of the Royal Astronomical Society Monthly Notices of the Royal Astronomical Society 496 (3), 3755-3766, 2020-06-22 Oxford University Press (OUP) 被引用文献 (8) *注記 読み込み中... もっと見る Tweet キーワード Earth and Planetary Astrophysics (astro-ph.EP) FOS: Physical sciences Astrophysics - Earth and Planetary Astrophysics 詳細情報 詳細情報について CRID 1360290617648842112 DOI 10.1093/mnras/staa1778 10.48550/arxiv.2006.09068 ISSN 13652966 00358711 Web Site http://academic.oup.com/mnras/advance-article-pdf/doi/10.1093/mnras/staa1778/33414797/staa1778.pdf http://academic.oup.com/mnras/article-pdf/496/3/3755/33485500/staa1778.pdf 資料種別 journal article データソース種別 Crossref KAKEN OpenAIRE 書き出し RefWorksに書き出し EndNoteに書き出し Mendeleyに書き出し RDFで書き出し Refer/BibIXで表示 RISで表示 BibTeXで表示 TSVで表示 CSVで表示 JSON-LDで表示 問題の指摘 論文情報の修正 その他 ページトップへ 現時点での人物検索の対象は、科研費報告書やresearchmapの記載に基づき研究者番号が推定された研究者等約30万人です。 ※詳しい説明はこちら