Hf-W-Thは,火星の急速な成長と惑星の胚としての地位の証拠です
1Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, 5734 South Ellis Avenue, Chicago, Illinois 60637, USA. dauphas@uchicago.edu
Nature
|May 27, 2011
まとめ
火星は急速な増殖を経験し,180万年以内に半分のサイズに達しました. これは,太陽系形成の初期に衝突を回避した惑星の胚として火星の理論を支持する.
科学分野:
- 惑星科学は惑星科学である.
- 宇宙化学 (コスモケミストリー)
- 地質物理学 地質物理学とは地質物理学です.
背景:
- 地上の惑星形成モデルでは,地球と金星とは異なり,火星の小さな大きさを説明するのに苦労しています.
- 火星の起源を理解するために決定的な火星の蓄積時間スケールの以前の推定は,火星のマントルのハフニウム / トングステン (Hf / W) の比率の不確実性のために,貧弱に制限されていました.
- 火星に関する既存の蓄積時間スケールは,0~1500万年 (Myr) の幅の広い範囲にある.
研究 の 目的:
- 火星の蓄積時間スケールとHf/W比率を正確に決定するために.
- 火星は,増殖から逃れた惑星の胚であったという仮説を検証するために.
- 地球上の惑星の形成と太陽系の初期進化のモデルを精錬する.
主な方法:
- ハフニウム-182 (182Hf) ボルンガム-182 (182W) 崩壊系をシェルゴッタイト,ナクリト,シャシニット隕石で利用した.
- コンドライトにおけるトリウム/ハフニウム (Th/Hf) とハフニウム176/ハフニウム177 (176Hf/177Hf) の比率との相関関係が,母体過程を補正するために確立された.
- 確立された相関を用いて,火星のマントルの正確なHf/W比を計算した.
主要な成果:
- 火星は急速に縮小し,現在の大きさの約半分に達した 1.8 Myr またはそれ以下.
- 火星のマントルの正確なHf/W比は3.51 ± 0.45.45であった.
- この急速な増殖は,火星が惑星の胚であることに一致する.
結論:
- 火星の急速な成長は,太陽系の歴史の初期に,星雲のガス散布の前に起こった.
- この発見は,火星の形成に関する" stranded embryo "仮説を裏付けている.
- 初期の蓄積は,潜在的にアルミニウム-26 (26Al) 崩壊によって動力を与えられるマグマ海洋の形成を可能にしました.
関連する概念動画
Acceleration due to Gravity on Other Planets
The gravitational acceleration of an object near the Earth's surface is called the acceleration due to gravity. It can be measured by conducting simple experiments on Earth. However, such an experiment is impossible to conduct on the surface of other planets.
Astronomical observations are thus used to measure the acceleration due to gravity on other planets. This can be determined by observing the effect of a planet's gravity on objects close to it. The crucial factor that helps in this...
Astronomical observations are thus used to measure the acceleration due to gravity on other planets. This can be determined by observing the effect of a planet's gravity on objects close to it. The crucial factor that helps in this...
Torque Free Motion
The torque-free motion refers to the movement of a rigid body in space when no external torques are acting upon it. This type of motion can be observed in environments where there are no external forces or frictions, like in outer space. For example, a rotation of Mars in space is a torque-free motion. Mars is an axisymmetric object, meaning it has an axis of symmetry along which it rotates, designated as the z-axis. The rotating frame of reference is defined such that the center of mass of...
Cleavage and Blastulation
After a large-single-celled zygote is produced via fertilization, the process of cleavage occurs while zygotes travel through the uterine tube. Cleavage is a mitotic cell division that does not result in growth. With each round of successive cell division, daughter cells get increasingly smaller.
Gastrulation
Gastrulation establishes the three primary tissues of an embryo: the ectoderm, mesoderm, and endoderm. This developmental process relies on a series of intricate cellular movements, which in humans transforms a flat, “bilaminar disc” composed of two cell sheets into a three-tiered structure. In the resulting embryo, the endoderm serves as the bottom layer, and stacked directly above it is the intermediate mesoderm, and then the uppermost ectoderm. Respectively, these tissue strata will form...
Cellular Adaptation III: Hyperplasia
Hyperplasia is an increase in the number of cells in a tissue or organ due to enhanced cell division. It is an adaptive, controlled response to stimuli such as injury, hormones, or stress, involving mitosis to produce genetically identical cells and support tissue repair and regeneration.Tissue CapacityCertain tissues, including the epidermis, intestinal epithelium, bone marrow, and fibroblasts, have a high potential for hyperplasia. Others, such as bone, cartilage, and smooth muscle, show...
Kepler's First Law of Planetary Motion
In the early 17th century, German astronomer and mathematician Johannes Kepler postulated three laws for the motion of planets in the solar system. He formulated his first two laws based on the observations of his forebears, Nikolaus Copernicus and Tycho Brahe.
Polish astronomer Nikolaus Copernicus put forth a theory that stated a heliocentric model for the solar system. According to this heliocentric theory, all the planets, including Earth, orbit the Sun in circular orbits.
On the other hand,...
Polish astronomer Nikolaus Copernicus put forth a theory that stated a heliocentric model for the solar system. According to this heliocentric theory, all the planets, including Earth, orbit the Sun in circular orbits.
On the other hand,...


