暖かい火星の斜面に季節の流れが流れています
Alfred S McEwen1, Lujendra Ojha, Colin M Dundas
1Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA. mcewen@lpl.arizona.edu
Science (New York, N.Y.)
|August 6, 2011
まとめ
火星上の再発性斜面線 (RSL) は,暖かい季節に現れ,成長し,一時的な液体塩水の可能性を示唆しています. 火星表面の正確な水源とRSL形成メカニズムを理解するためにさらなる研究が必要です.
科学分野:
- 惑星科学は惑星科学である.
- 地質学 地質学 地質学
- 天体生物学 アストロバイオロジー
背景:
- 古代の火星には地表水があったと考えられていますが,現在の液体の水の存在は議論されています.
- 再発性斜面線 (RSL) は,火星の斜面に観測された暗い狭いマークです.
- RSLは季節的な変化を示し,より暖かい時期に現れ,成長し,より寒い時期に衰退します.
研究 の 目的:
- 火星上の再発性斜面線 (RSL) の性質と潜在的な原因を調査する.
- RSLの活動が一時的な液体の水または塩水の存在と関連しているかどうかを判断する.
- RSLの季節的行動と形成メカニズムを理解する.
主な方法:
- 火星偵察軌道探査機の高解像度イメージング科学実験 (HiRISE) の繰り返し画像の分析.
- 火星の季節にわたるRSLの出現,成長,衰退のパターンの観察.
- RSLの活動と火星の特定の緯度,傾斜角度,表面温度との相関.
主要な成果:
- RSLは,特定の緯度 (48°Sから32°S) で南部の晩春と夏の間に現れ,伸びます.
- RSLの活動は,赤道に面した斜面を好み,表面のピーク温度は約250〜300ケルヴィンである.
- RSLは,岩盤の露出点と小さな運河と関連しており,いくつかの場所では何百もの運河が形成されています.
結論:
- RSLの季節的振る舞いは,火星表面の近くにある一時的な液体塩水の存在と一致しています.
- RSLの形成に関与する正確なメカニズムと水の起源は未だに不明である.
- RSLは,火星の現在の水活動を理解するための重要な現象を表しています.
関連する概念動画
01:23States of Water
46.5K
Water exists in any one of the three classical states: solid (ice), liquid (water), and gas (steam or water vapor). The state of water depends on i) the intermolecular forces that draw molecules together and ii) the kinetic energy that leads to movements that pull them apart.
Water freezes when the intermolecular forces are greater than the kinetic energy. Unlike most other substances, water is less dense in its solid state than in its liquid state. This is because each water molecule can form...
Water freezes when the intermolecular forces are greater than the kinetic energy. Unlike most other substances, water is less dense in its solid state than in its liquid state. This is because each water molecule can form...
46.5K
02:44Heating and Cooling Curves
23.2K
When a substance—isolated from its environment—is subjected to heat changes, corresponding changes in temperature and phase of the substance is observed; this is graphically represented by heating and cooling curves.
For instance, the addition of heat raises the temperature of a solid; the amount of heat absorbed depends on the heat capacity of the solid (q = mcsolidΔT). According to thermochemistry, the relation between the amount of heat absorbed or released by a substance,...
For instance, the addition of heat raises the temperature of a solid; the amount of heat absorbed depends on the heat capacity of the solid (q = mcsolidΔT). According to thermochemistry, the relation between the amount of heat absorbed or released by a substance,...
23.2K
01:21Masonry in Cold and Hot Weather Conditions
416
In cold weather, masonry construction requires specific precautions to ensure mortar does not freeze before curing, as this can significantly weaken its strength and watertightness. Mortar temperature should be maintained between 60°F and 80°F to support proper hydration and curing. Below 40°F, mortar water must be heated, but should not exceed 120°F as high temperatures can reduce mortar's compressive and bond strength.
Other key practices include keeping masonry units...
Other key practices include keeping masonry units...
416
01:28Irrotational Flow
1.3K
Irrotational flow is characterized by fluid motion where particles do not rotate around their axes, resulting in zero vorticity. For a flow to be irrotational, the curl of the velocity field must be zero. This imposes specific conditions on velocity gradients. For instance, to maintain zero rotation about the z-axis, the gradient condition:
1.3K
01:22Couette Flow
1.4K
Couette flow represents the flow of fluid between two parallel plates, with one plate fixed and the other moving with a constant velocity. This configuration allows for a simplified analysis using the Navier-Stokes equations, which govern fluid motion under conditions of viscosity and incompressibility. For Couette flow, the assumptions include a steady, laminar, incompressible flow with a zero-pressure gradient in the flow direction. This flow type is beneficial for understanding shear-driven...
1.4K
01:29Gradually Varying Flow
700
Gradually varying flow (GVF) in open channels describes situations where water depth changes slowly along the channel due to factors like non-uniform bed slope, channel shape variations, or obstructions. This flow type occurs when the depth adjusts gradually to balance gravitational forces, shear forces, and energy requirements, resulting in a low rate of depth change.Characteristics of Gradually Varying FlowGVF is commonly observed in natural streams, rivers, and canals, where flow depth...
700