Consider the terrestrial worlds in your Mystery Solar System . Which of these mi
ID: 106668 • Letter: C
Question
Consider the terrestrial worlds in your Mystery Solar System. Which of these might be a home for life? Consider temperature, atmosphere, and any other properties that might affect the presence of life. Also select at least 2 other terrestrial worlds and explain what is right and wrong about these worlds.
(The Mystery Solar System is not the one which we are located, is a imaginary one, solve the question according to the data in table.)
Known Planets 5 1 Earth mass 6 x 10 24 kg Inner Solar System 3 1 Earth Radius 6.4 x 10M6 m Outer Solar System 1 AU 1.5 x 10M8 km Wavele Orbit ngth Inner Solar Mass Distance Period Tilt Radius No Light System (Earth From Star (Earth Spin (degrees (Earth Reflectivit Greenhouse Emitted Large Small years) (hours) Radii) y Temp (KK) (nm) Moons Moons 0.130 0.16 0.06 525.0 154.0 0.55 072 510 5669 0 Planets Masses) (AU) 0.630 0.46 0.30 9.17 80.7 0.87 0.43 358 7626 1 3 0.398 0.87 0.77 43.1 106.9 0.76 0.39 265 6814 4 0.497 1.23 1.29 11.4 99.6 0.84 051 211 7272 1.87 2.41 23.8 128.9 1.03 0.34 185 8191 1 0 1.092 Wavelength Outer Solar Mass Distance Orbit Tilt Radius Light System (Earth From Star Period Spin (degrees (Earth Reflectivit Emitted Large Small Radii Planets Masses) (AU) (years) (hours) y (nm) Moons Moons 51749 6.79 16.7 6.5 0.6 11.89 052 32421 3.000 233 27 95 21.59 947 8.17 36.0 5.09 050 57349 0.000 7 3 27 5.75 4791 312.99 12.4 1.8 10.12 0.49 84801 5.000 30 An axis tilt 90 degrees implies that the planet is spinning retrograde (opposite its orbit direction) Reflectivity is the fraction of starlight reflected by the planet back to space The no-greenhouse temperature depends on the albedo and the distance from the star. It may not match the actual surface temperature. The wavelength of light emitted is the peak wavelength of thermal emission from the planet. Use this to calculate temperature Large Moons are defined as having a mass greater than 0.002 Earth masses or 10 22 kgExplanation / Answer
All of the terrestrial planets have the similar structure of 3 basic regions: a core of iron (with maybe some other materials like nickel), a mantle of silicates (rock) and a lithosphere or crust. While the crust is solid, the mantle and core can be solid or liquid, depending on how hot it is and its chemical composition. The hotter the core or mantle, the more likely it is convecting--that is, flowing or turning over. A convecting mantle leads to buckling of the crust - tectonics. A convecting iron core will generate a magnetic field. All five of the terrestrial bodies - Earth, Venus, Mars, Mercury, and Moon - have this same 3-part structure. Below is a diagram showing the relative sizes of the planets themselves and of their cores.
Processes that Heat a Planet
Accretion - Process of the planet being formed by bits of rock and iron, etc; clumping together. As they collide, the energy of the collisions is converted into thermal energy. The bigger the planet, the more material that is accreted -> the greater the heating.
Differentiation - After the material has clumped together to form a planet and IF the interior heated up enough to melt, then the denser material (e.g. iron) sinks down to the center and the lighter material (e.g. rock) floats to the top. The sinking of denser material releases energy - in a similar way to dropping an object onto the floor leads to release of energy (dissipated as heat, sound and/or breaking up the object dropped). There is evidence that this process is continuing to occur, slowly, inside some of the planets. For example, the freezing out of iron from the liquid outer core onto the inner solid core is thought to be the source of energy to drive the magnetic dynamo inside the Earth.
Radioactivity - The rocks in a planet are radioactive - there are elements that are unstable and split up (fission) into 'mother' and 'daughter' elements. In the process, energy is released. The amount of radioactivity in a rock decreases with time (exponentially). The time for the radioactivity to drop by half is called the "half-life". Each radioactive element has a different, specific half-life. Some half-lives are short (few million years - e.g. Plutonium(241) has 2.4 million years) compared with the age of planets - this means that very few of the radioactive "mother" isotopes are left in the planets by now. But some elements have much longer half-lives - for example, Uranium(238) at 4.5 billion years and Thorium (232) at 13.9 billion years, - and are still generating heat inside the planets. Long-lived radioactive elements tend to be chemically bound to silicates (rocks) rather than to iron (in the core) or to water (such as the Earth's ocean, or the icy mantle or crust of outer solar system bodies). This is the main source of energy for the terrestrial planets today.
Processes that Cool a Planet
Conduction: - this is heat lost through "touching" (think of putting a metal rod in the fire, or a metal fork on a gas burner - one end of the rod heats up and slowly the heat moves up along the road until you eventually feel the heat in your hand). This is a relatively slow way for heat to be transported.
Convection: - when a liquid is heated from below and cooled from above the liquid begins to flow, turnover - hot material rising and cool material sinking. This is what happens with soup in a saucepan - also with the mantle when heated up. This is an efficient way to remove heat from the inside.
Eruption: - an eruption of hot lava carries heat from inside - but it is only the top layers of the mantle that lose heat this way.
Radiation: - all planets radiate infrared radiation from the surface. But this only cools off the very top surface layer - just a few feet.
Density provides the first clues about the planet's interior. Other clues are provided by measurements of the magnetic field and, if we get the chance to land on the object put instruments on the surface, by seismometers. The process whereby a magnetic field is generated inside a planet (or stars, for that matter) is not well understood. It is known, however, that there are 3 necessary ingredients:
A region containing an electrically conducting fluid (such as liquid iron)
Rotation
A source of energy, to stir up the conducting fluid - make it convection
The result is a global magnetic field (as if there was a large bar magnet in the center) which extends well beyond the planet and can be measured by a passing spacecraft. It turns out (we have recently realized) that all of the planets (and their moons) probably have sufficient rotation so that the existence (or absence) of a magnetic field really tells us whether or not there is a substantial region of liquid iron (or similarly conducting material - rock is much less conductive than iron)
Surface Processes
Now that we have some sense of the interiors of the terrestrial planets, we will next look at their surfaces and relate what we see to the processes that sculpt them.
Impact Cratering
Volcanism s
Tectonics
Erosion
Tectonics
Tectonics is basically the cracking of a planet's crust (lithosphere)--these faults can be caused by the whole planet (or regions) expanding or shrinking or because parts of the crust are being pushed or pulled because of underlying molten material (asthenosphere) is moving and turning over (convection)
Erosion
The previous geological processes--cratering, volcanism and tectonics--occur on large scales, 10s to 1000s of km (the scale of a State rather than a town). Erosion--the process of wearing down the landscape by wind, rain, snow and ice--acts on small scales, removing rock grain by grain--but over long periods of time can have large-scale effects (such as the Grand Canyon). Click on this diagram of a river drainage system for an illustration of how small scale tributaries combine to form a large scale river system.