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10:11). Sentinel Mission: Finding an Asteroid Headed for Earth: https://www.youtube.com/watch?v=efz8c3ijD_A. Public lecture by astronaut Ed Lu (1:08:57). COLLABORATIVE GROUP ACTIVITIES A. If we can predict that lots of ground movement takes place along subduction zones and faults, then why do so many people live there?... |
E. Is there evidence of climate change in your area over the past century? How would you distinguish a true climate change from the random variations in weather that take place from one year to the next? EXERCISES Review Questions 1. What is the thickest interior layer of Earth? The thinnest? 2. What are Earth’s core ... |
/icy one? 20. If all life were destroyed on Earth by a large impact, would new life eventually form to take its place? Explain how conditions would have to change for life to start again on our planet. 21. Why is a decrease in Earth’s ozone harmful to life? 22. Why are we concerned about the increases in CO2 and other ... |
entire volume does this annual addition of new material represent? 28. Suppose a major impact that produces a mass extinction takes place on Earth once every 5 million years. Suppose further that if such an event occurred today, you and most other humans would be killed (this would be true even if the human species as... |
sources. Because its airless surface preserves events that happened long ago, the Moon provides a window on earlier epochs of solar system history. The planet Mercury is in many ways similar to the Moon, which is why the two are discussed together: both are relatively small, lacking in atmospheres, deficient in geolog... |
.4 0.38 4.3 58.65 Chapter 9 Cratered Worlds 305 Properties of the Moon and Mercury Property Moon Mercury Surface area (Earth = 1) 0.27 0.38 Table 9.1 Exploration of the Moon Most of what we know about the Moon today derives from the US Apollo program, which sent nine piloted spacecraft to our satellite between 1968 and... |
; 95 kilograms of samples returned Apollo 17 Dec. 1972 Taurus-Littrow highlands Geologist among the crew; 111 kilograms of samples returned Table 9.2 Figure 9.3. Scientist on the Moon. Geologist (and later US senator) Harrison “Jack” Schmitt in front of a large boulder in the Littrow Valley at the edge of the lunar hig... |
bizarre piece of irony, a few people even question whether we went to the Moon at all, proposing instead that the Apollo program was a fake, filmed on a Hollywood sound stage. See the Link to Learning box below for some scientists’ replies to such claims.) However, scientific interest in the Moon is stronger than ever... |
in iron and other metals. It is as if the Moon were composed of the same silicates as Earth’s mantle and crust, with the metals and the volatiles selectively removed. These differences in composition between Earth and Moon provide important clues about the origin of the Moon, a topic we will cover in detail later in t... |
on routes to Mars and the rest of the solar system. If the ice could be mined, it would yield both water and oxygen for human support, and it could be broken down into hydrogen and oxygen, a potent rocket fuel. 310 Chapter 9 Cratered Worlds 9.2 THE LUNAR SURFACE Learning Objectives By the end of this section, you will... |
NASA/Goddard/Arizona State University) Lunar History To trace the detailed history of the Moon or of any planet, we must be able to estimate the ages of individual rocks. Once lunar samples were brought back by the Apollo astronauts, the radioactive dating techniques that had been developed for Earth were applied to t... |
of the lunar surface, mostly on the side of the Moon that faces Earth (Figure 9.9). Figure 9.9. Lunar Maria. About 17% of the Moon’s surface consists of the maria—flat plains of basaltic lava. This view of Mare Imbrium also shows numerous secondary craters and evidence of material ejected from the large crater Coperni... |
which involved the release of lava from hundreds of kilometers below the surface, ended about 3.3 billion years ago. After that, the Moon’s interior cooled, and volcanic activity was limited to a very few small areas. The primary forces altering the surface come from the outside, not the interior. 314 Chapter 9 Crater... |
to the Moon we see today. See a simulation of how the Moon’s craters and maria were formed through periods of impact, volcanic activity, and heavy bombardment. 1 You can see the cycle of day and night on the side of the Moon facing us in the form of the Moon’s phases. It takes about 14 days for the side of the Moon fa... |
on Earth. Terrestrial volcanic craters are smaller and deeper and almost always occur at the tops of volcanic mountains (Figure 9.13). The only alternative to explain the Moon’s craters was an impact origin. His careful reasoning, although not accepted at the time, laid the foundations for the modern science of lunar ... |
izes and a shock wave spreads through the lunar rock. (c) Ejecta are thrown out of the crater. (d) Most of the ejected material falls back to fill the crater, forming an ejecta blanket. An impact explosion of the sort described above leads to a characteristic kind of crater, as shown in Figure 9.15. The central cavity ... |
and in this flat lighting, no shadows are cast. Much more revealing is the view near first or third quarter, when sunlight streams in from the side, causing topographic features to cast sharp shadows. It is almost always more rewarding to study a planetary surface under such oblique lighting, when the maximum informat... |
R EPIC team) This OpenStax book is available for free at http://cnx.org/content/col11992/1.8 Chapter 9 Cratered Worlds 319 One interesting thing about the Moon that you can see without binoculars or telescopes is popularly called “the new Moon in the old Moon’s arms.” Look at the Moon when it is a thin crescent, and yo... |
. This result is similar to the age determined for the maria from radioactive dating of returned samples—3.3 to 3.8 billion years old. The fact that these two calculations agree suggests that astronomers’ original assumption was right: comets and asteroids in approximately their current numbers have been impacting plan... |
current “giant impact” concept of how the Moon formed It is characteristic of modern science to ask how things originated. Understanding the origin of the Moon has proven to be challenging for planetary scientists, however. Part of the difficulty is simply that we know so much This OpenStax book is available for free ... |
. The Giant Impact Hypothesis In an effort to resolve these apparent contradictions, scientists developed a fourth hypothesis for the origin of the Moon, one that involves a giant impact early in Earth’s history. There is increasing evidence that large chunks of material—objects of essentially planetary mass—were orbit... |
similar to the Moon in many ways. Like the Moon, it has no atmosphere, and its surface is heavily cratered. As described later in this chapter, it also shares with the Moon the likelihood of a violent birth. Mercury’s Orbit Mercury is the nearest planet to the Sun, and, in accordance with Kepler’s third law, it has th... |
liquid in order to generate the observed magnetic field.[3] 3 Recall from the Radiation and Spectra chapter that magnetism is an effect of moving electric charges. In atoms of metals, the outer electrons are easier to dislodge and they can form a current when the metal is in liquid form and can flow. This OpenStax boo... |
frequency into a range of frequencies in the reflected signal (Figure 9.21). The degree of broadening provides an exact measurement of the rotation rate of the planet. Figure 9.21. Doppler Radar Measures Rotation. When a radar beam is reflected from a rotating planet, the motion of one side of the planet’s disk toward... |
same place in Mercury’s sky turns out to be two Mercury years, or 176 Earth days. (Note that this result is not intuitively obvious, so don’t be upset if you didn’t come up with it.) Thus, if one day at noon a Mercury explorer suggests to her companion that they should meet at noon the next day, this could mean a very... |
before, one of the best things about taking an astronomy class should be ridding you forever of any “Earth chauvinism” you might have. The way things are on our planet is just one of the many ways nature can arrange reality. 326 Chapter 9 Cratered Worlds The Surface of Mercury The first close-up look at Mercury came i... |
) This OpenStax book is available for free at http://cnx.org/content/col11992/1.8 Chapter 9 Cratered Worlds 327 Figure 9.23. Caloris Basin. This partially flooded impact basin is the largest known structural feature on Mercury. The smooth plains in the interior of the basin have an area of almost two million square kil... |
for the Moon’s lack of a metal core. Mercury is likely to have experienced several giant impacts very early in its youth, and one or more of these may have torn away a fraction of its mantle and crust, leaving a body dominated by its iron core You can follow some of NASA’s latest research on Mercury (https://openstax.... |
-speed impacts produce explosions and excavate craters 10 to 15 times the size of the impactor with raised rims, ejecta blankets, and often central peaks. Cratering rates have been roughly constant for the past 3 billion years but earlier were much greater. Crater counts can be used to derive approximate ages for geolo... |
. What was done with the rocks the astronauts brought back from the Moon. Schmitt, H. “Exploring Taurus–Littrow: Apollo 17.” National Geographic (September 1973). First-person account given by the only scientist to walk on the Moon. Schmitt, H. “From the Moon to Mars.” Scientific American (July 2009): 36. The only scie... |
Cratered Worlds 331 Sheehan, W., and Dobbins, T. “Mesmerized by Mercury.” Sky & Telescope (June 2000): 109. History of Mercury observations and how amateur astronomers can contribute. Talcott, R. “Surprises from MESSENGER’s Historic Mercury Fly-by.” Astronomy (March 2009): 28. Talcott, R. “Mercury Reveals its Hidden S... |
://solarviews.com/eng/mercury.htm. COLLABORATIVE GROUP ACTIVITIES A. We mentioned that no nation on Earth now has the capability to send a human being to the Moon, even though the United States once sent 12 astronauts to land there. What does your group think about this? Should we continue the exploration of space with... |
are named for writers, artists, composers, and others in the humanities. See the official list at: http://planetarynames.wr.usgs.gov/SearchResults? target=MERCURY&featureType=Crater,%20craters). Living persons are not eligible. Can each person in your group think of a scientist or someone in the arts whom they especia... |
Moon’s origin? 15. What is the main consequence of Mercury’s orbit being so highly eccentric? 16. Describe the basic internal structure of Mercury. 17. How was the rotation rate of Mercury determined? 18. What is the relationship between Mercury’s rotational period and orbital period? 19. The features of Mercury are n... |
humans raised on Earth might deal with time cycles on Mercury? 31. The Moon has too little iron, Mercury too much. How can both of these anomalies be the result of giant impacts? Explain how the same process can yield such apparently contradictory results. Figuring For Yourself 32. In the future, astronomers discover ... |
. In contrast, the larger terrestrial planets—Earth, Venus, and Mars—are more active and interesting worlds. We have already discussed Earth, and we now turn to Venus and Mars. These are the nearest planets and the most accessible to spacecraft. Not surprisingly, the greatest effort in planetary exploration has been de... |
Pioneer Venus Orbiter. This ultraviolet image shows an upper-atmosphere cloud structure that would be invisible at visible wavelengths. Note that there is not even a glimpse of the planet’s surface. (credit: modification of work by NASA) In contrast, Mars is more tantalizing as seen through a telescope (Figure 10.3). ... |
will see shortly.) Until has death in 1916, the most effective proponent of intelligent life on Mars was Percival Lowell, a self-made American astronomer and member of the wealthy Lowell family of Boston (see the feature box on Percival Lowell: Dreaming of an Inhabited Mars). A skilled author and speaker, Lowell made ... |
however, he decided to dedicate himself to carrying on Schiaparelli’s work and solving the mysteries of the martian canals. This OpenStax book is available for free at http://cnx.org/content/col11992/1.8 Chapter 10 Earthlike Planets: Venus and Mars 339 In 1894, with the help of astronomers at Harvard but using his own... |
his claims about Mars caused far more than the astronomers on the other side, who often complained that Lowell’s work was making planetary astronomy a less respectable field. At the same time, the public fascination with the planets fueled by Lowell’s work (and its interpreters) may, several generations later, have he... |
ar features” across its disk, is 243 days. Even more surprising than how long Venus takes to rotate is the fact that it spins in a backward or retrograde direction (east to west). This OpenStax book is available for free at http://cnx.org/content/col11992/1.8 Chapter 10 Earthlike Planets: Venus and Mars 341 Stop for a ... |
.2 5.3 0.91 10.4 3.9 0.38 5.0 Rotation period (hours or days) 23.9 h 243 d 24.6 h Surface area (Earth = 1) Atmospheric pressure (bar) Table 10.1 1.00 1.00 0.90 90 0.28 0.007 Mars, by contrast, is rather small, with a mass only 0.11 times the mass of Earth. It is larger than either the Moon or Mercury, however, and, unl... |
similar in both cases: use a radar instrument to probe through the obscuring layer. The first global radar map was made by the US Pioneer Venus orbiter in the late 1970s, followed by better maps from the twin Soviet Venera 15 and 16 radar orbiters in the early 1980s. However, most of our information on the geology of ... |
be naked, revealing the history of hundreds of millions of years of geological activity. About 75% of the surface of Venus consists of lowland lava plains. Superficially, these plains resemble the basaltic ocean basins of Earth, but they were not produced in quite the same way. There is no evidence of subduction zones... |
crater rims and ejecta appear brighter in these radar images than do the smoother surrounding lava plains. The largest of these craters has a diameter of 50 kilometers. (b) This small, complex crater is named after writer Gertrude Stein. The triple impact was caused by the breaking apart of the incoming asteroid durin... |
In the lowland plains, volcanic eruptions are the principal way the surface is renewed, with large flows of highly fluid lava destroying old craters and generating a fresh surface. In addition, numerous younger volcanic mountains and other structures are associated with surface hot spots—places where convection in the... |
pancake volcano in the upper center of the image). (credit: NASA/JPL) Tectonic Activity Convection currents of molten material in the mantle of Venus push and stretch the crust. Such forces are called tectonic, and the geological features that result from these forces are called tectonic features. On Venus’ lowland pl... |
of rocks, some of which may be ejecta from impacts. Other areas show flat, layered lava flows. There have been no further landings on Venus since the 1970s. Figure 10.11. Surface of Venus. These views of the surface of Venus are from the Venera 13 spacecraft. Everything is orange because the thick atmosphere of Venus ... |
03% 78.1% 0.93% 21.0% 0.002% 96% 3.5% 0.006% 0.003% 0.001% 95.3% 2.7% 1.6% 0.15% 0.0003% The atmosphere of Venus has a huge troposphere (region of convection) that extends up to at least 50 kilometers above the surface (Figure 10.12). Within the troposphere, the gas is heated from below and circulates slowly, rising ne... |
Venus just as it does on Earth, but since Venus has so much more CO2—almost a million times more—the effect is much stronger. The thick CO2 acts as a blanket, making it very difficult for the infrared (heat) radiation from the ground to get back into space. As a result, the surface heats up. The energy balance is only... |
Earth, most of the CO2 is either chemically bound in the rocks of our crust or dissolved by the water in our oceans. As Venus got hotter and hotter, its oceans evaporated, eliminating that safety valve. But the water vapor in the planet’s atmosphere will not last forever in the presence of ultraviolet light from the S... |
toward Mars, but only about half were fully successful. The first visitor was the US Mariner 4, which flew past Mars in 1965 and transmitted 22 photos to Earth. These pictures showed an apparently bleak planet with abundant impact craters. In those days, craters were unexpected; some people who were romantically incli... |
of gullies apparently cut by surface water, as we will discuss later. These missions were followed in 2003 by the NASA Mars Odyssey orbiter, and the ESA Mars Express orbiter, both carrying high-resolution cameras. A gamma-ray spectrometer on Odyssey discovered a large amount of subsurface hydrogen (probably in the for... |
directly measured water ice in the soil. Figure 10.15. Victoria Crater. (a) This crater in Meridiani Planum is 800 meters wide, making it slightly smaller than Meteor crater on Earth. Note the dune field in the interior. (b) This image shows the view from the Opportunity rover as it scouted the rim of Victoria crater ... |
10.16)—rocks that have fallen from space. Figure 10.16. Martian Meteorite. This fragment of basalt, ejected from Mars in a crater-forming impact, eventually arrived on Earth’s surface. (credit: NASA) How would rocks have escaped from Mars? Many impacts have occurred on the red planet, as shown by its heavily cratered ... |
, giving it a total surface area very nearly equal to the continental (land) area of our planet. Its overall density of 3.9 g/cm3 suggests a composition consisting primarily of silicates but with a small metal core. The planet has no global magnetic field, although 354 Chapter 10 Earthlike Planets: Venus and Mars there... |
formed between 3 and 4 billion years ago. Apparently, Mars experienced extensive volcanic activity at about the same time the Moon did, producing similar basaltic lavas. The largest volcanic mountains of Mars are found in the Tharsis area (you can see them in Figure 10.17), although smaller volcanoes dot much of the s... |
on Mars are the canyons called the Valles Marineris (or Mariner Valleys, named after Mariner 9, which first revealed them to us), which are shown in Figure 10.19. They extend for about 5000 kilometers (nearly a quarter of the way around Mars) along the slopes of the Tharsis bulge. If it were on Earth, this canyon syst... |
In part, this may reflect a lower general level of geological activity, as would be expected for a smaller planet. But it is also possible that evidence of widespread faulting has been buried by wind- deposited sediment over much of Mars. Like Earth, Mars may have hidden part of its geological history under a cloak of... |
were about 173 K (–100 °C). During the winter, Viking 2 also photographed water frost deposits on the ground (Figure 10.22). We make a point of saying “water frost” here because at some locations on Mars, it gets cold enough for carbon dioxide (dry ice) to freeze out of the atmosphere as well. Figure 10.22. Water Fros... |
the end of this section, you will be able to: Describe the general composition of the atmosphere on Mars Explain what we know about the polar ice caps on Mars and how we know it Describe the evidence for the presence of water in the past history of Mars Summarize the evidence for and against the possibility of life on... |
which the main character is stranded on Mars after being buried in the sand in a windstorm so great that his fellow astronauts have to leave the planet so their ship is not damaged. Astronomers have noted that the martian winds could not possibly be as forceful as depicted in the film. In most ways, however, the depic... |
) This is a composite image of the north pole in summer, obtained in October 2006 by the Mars Reconnaissance Orbiter. It shows the mostly water-ice residual cap sitting atop light, tan-colored, layered sediments. Note that although the border of this photo is circular, it shows only a small part of the planet. (b) Here... |
, marked by alternating light and dark bands of sediment. Probably the material in the polar deposits includes dust carried by wind from the equatorial regions of Mars. What do these terraced layers tell us about Mars? Some cyclic process is depositing dust and ice over periods of time. The time scales represented by t... |
2 km thick and has a radius of 400 km (the area of a circle is πR2). Solution The volume of Earth’s water is therefore the area 4πR2 ⎞ ⎛ ⎝6.378 × 106 m 4π ⎠ 2 = 5.1 × 1014 m2 This OpenStax book is available for free at http://cnx.org/content/col11992/1.8 Chapter 10 Earthlike Planets: Venus and Mars 363 multiplied by t... |
a few meters deep, some tens of meters wide, and perhaps 10 or 20 kilometers long (Figure 10.27). They are called runoff channels because they look like what geologists would expect from the surface runoff of ancient rain storms. These runoff channels seem to be telling us that the planet had a very different climate ... |
of water feature, the smaller gullies, was discovered by the Mars Global Surveyor (Figure 10.28). The Mars Global Surveyor’s camera images achieved a resolution of a few meters, good enough to see something as small as a truck or bus on the surface. On the steep walls of valleys and craters at high latitudes, there ar... |
. The dark streaks in Horowitz crater, which move downslope, have been called recurring slope lineae. The streaks in the center of the image go down the wall of the crater for about a distance of 100 meters. Spectra taken of this region indicate that these are locations where salty liquid water flows on or just below t... |
. Gale Crater. (a) This scene, photographed by the Curiosity rover, shows an ancient lakebed of cracked mudstones. (b) Geologists working with the Curiosity rover interpret this image of cross-bedded sandstone in Gale crater as evidence of liquid water passing over a loose bed of sediment at the time this rock formed. ... |
, in Orbit 220, the MOC obtained an oblique image of the face at a resolution of 4 meters per pixel, a factor-of-10 improvement in resolution over the Viking image. Another image in 2001 had even higher resolution. Immediately released by NASA, the new images showed a low mesa-like hill cut crossways by several roughly... |
actually it was a balloon carrying scientific instruments to find evidence of Soviet nuclear tests), or the notion that alien astronauts helped build the Egyptian pyramids and many other ancient monuments because our ancestors were too stupid to do it alone. In response to the increase in publicity given to these “fict... |
produce a temporary atmosphere that is thick enough to permit liquid water on the surface for a few weeks or months. Some have even suggested that future technology might allow us to terraform Mars—that is, to engineer its atmosphere and climate in ways that might make the planet more hospitable for long-term human ha... |
two planets had very similar surface conditions then. Thus, the attention of scientists has shifted to the search for fossil life on Mars. One of the primary questions to be addressed by future spacecraft is whether Mars once supported its own life forms and, if so, how this martian life compared with that on our own ... |
inside some of the returned samples. In fact, Mars is sending samples to Earth all the time in the form of the Mars meteorites. Since some of these microbes (if they exist) could probably survive the trip to Earth inside their rocky home, we may have been exposed many times over to martian microbes. Either they do not... |
study of the terrestrial planets and their divergent evolutionary histories. 372 Chapter 10 Earthlike Planets: Venus and Mars CHAPTER 10 REVIEW KEY TERMS runaway greenhouse effect the process by which the greenhouse effect, rather than remaining stable or being lessened through intervention, continues to grow at an in... |
oes; Olympus Mons is more than 20 kilometers high and 500 kilometers in diameter. The Valles Marineris canyons are tectonic features widened by erosion. Early landers revealed only barren, windswept plains, but later missions have visited places with more geological (and scenic) variety. Landing sites have been selecte... |
. Robinson, C. “Magellan Reveals Venus.” Astronomy (February 1995): 32. Stofan, E. “The New Face of Venus.” Sky & Telescope (August 1993): 22. Zimmerman, R. “Taking Venus by Storm.” Astronomy (October 2008): 66. On results from the Venus Express mission. Mars Albee, A. “The Unearthly Landscapes of Mars.” Scientific Ame... |
remarkable close-up images it is sending. Talcott, R. “Seeking Ground Truth on Mars.” Astronomy (October 2009): 34. How rovers and orbiters are helping scientists understand the red planet’s surface. Websites European Space Agency Mars Express Page: http://www.esa.int/Our_Activities/Space_Science/Mars_Express. Europea... |
What It’s Like to be an Interplanetary Explorer: https://www.youtube.com/ watch?v=nRpCOEsPD54. 2013 talk by Dr. Lori Fenton about what it’s like on the surface of Mars (1:07:24). Magellan Maps Venus: http://www.bbc.co.uk/science/space/solarsystem/space_missions/ magellan_probe#p005y07s. BBC clip with Dr. Ellen Stofan ... |
more detailed information about Venus’ atmosphere, surface, and interior. D. Sometime late in the twenty-first century, when travel to Mars has become somewhat routine, a very wealthy couple asks you to plan a honeymoon tour of Mars that includes the most spectacular sights on the red planet. Constitute your group as ... |
suggests that it must have been different in the past? 5. Explain the runaway refrigerator effect and the role it may have played in the evolution of Mars. 6. What evidence do we have that there was running (liquid) water on Mars in the past? What evidence is there for water coming out of the ground even today? 7. Wha... |
and Venus. In each case, describe what kind of protective gear they would have to carry, and what their chances for survival would be if their spacesuits ruptured. 22. We believe that Venus, Earth, and Mars all started with a significant supply of water. Explain where that water is now for each planet. 23. One source ... |
is the fastest speed so far of any space vehicle launched from Earth. How long would it take to get to Mars at the time of closest approach? 378 Chapter 10 Earthlike Planets: Venus and Mars This OpenStax book is available for free at http://cnx.org/content/col11992/1.8 Chapter 11 The Giant Planets 379 11 THE GIANT PLA... |
material available to build these planets can be divided into three classes by what they are made of: “gases,” “ices,” and “rocks” (see Table 11.1). The “gases” are primarily hydrogen and helium, the most abundant elements in the universe. The way it is used here, the term “ices” refers to composition only and not whe... |
as CO2). As a result, the compounds detected in the atmosphere of the giant planets are mostly hydrogen-based gases such as methane (CH4) and ammonia (NH3), or more complex hydrocarbons (combinations of hydrogen and carbon) such as ethane (C2H6) and acetylene (C2H2). Exploration of the Outer Solar System So Far Eight ... |
pathfinders to Jupiter. One of their main objectives was simply to determine whether a spacecraft could actually navigate through the belt of asteroids that lies beyond Mars without getting destroyed by collisions with asteroidal dust. Another objective was to measure the radiation hazards in the magnetosphere (or zon... |
receiver had stopped working. The “brains” had significant “memory loss”: some of the onboard computer memory had failed. And the whole spacecraft was beginning to run out of energy: its generators had begun showing serious signs of wear. To make things even more of a challenge, Voyager’s mission at Neptune was in man... |
any probe has so far entered the atmosphere of a planet, and it put great demands on the heat shield protecting it. The high entry speed was a result of acceleration by the strong gravitational attraction of Jupiter. Atmospheric friction slowed the probe within 2 minutes, producing temperatures at the front of its hea... |
work by NASA/JPL-Caltech/Space Science Institute) 11.2 THE GIANT PLANETS Learning Objectives By the end of this section, you will be able to: Describe the basic physical characteristics, general appearance, and rotation of the giant planets Describe the composition and structure of Jupiter, Saturn, Uranus, and Neptune... |
planets. (Recall that water has a density of 1 g/cm3.) Jupiter’s material is spread out over a volume so large that more than 1400 Earths could fit within it. Saturn’s mass is 95 times that of Earth, and its average density is only 0.7 g/cm3—the lowest of any planet. Since this is less than the density of water, Satur... |
free at http://cnx.org/content/col11992/1.8 Chapter 11 The Giant Planets 387 brief video made from Hubble Space Telescope photos shows the rotation of Jupiter (https://openstax.org/l/30HSTJupRot) with its many atmospheric features. Remember that Earth and Mars have seasons because their spin axes, instead of “standing... |
southern hemisphere was experiencing a 21-year sunlit summer, while during that same period the northern hemisphere was plunged into darkness. For the next 21-year season, the Sun shines on Uranus’ equator, and both hemispheres go through cycles of light and dark as the planet rotates (Figure 11.6). Then there are 21 ... |
, this liquid hydrogen is further compressed and begins to act like a metal, something it never does on Earth. (In a metal, electrons are not firmly attached to their parent nuclei but can wander around. This is why metals are such good conductors of electricity.) On Jupiter, the greater part of the interior is liquid ... |
, being the largest, was the hottest. Some of this primordial heat can still remain inside such large planets. In addition, it is possible for giant, largely gaseous planets to generate heat after formation by slowly contracting. (With so large a mass, even a minuscule amount of shrinking can generate significant heat.... |
planet’s own magnetic field dominates over the general interplanetary magnetic field. The magnetospheres of these planets are their largest features, extending millions of kilometers into space. In the late 1950s, astronomers discovered that Jupiter was a source of radio waves that got more intense at longer rather th... |
case, Io, one of its moons, turns out to have volcanic eruptions that blast charged particles into space and right into the jovian magnetosphere. The axis of Jupiter’s magnetic field (the line that connects the magnetic north pole with the magnetic south pole) is not aligned exactly with the axis of rotation of the pl... |
actually the dominant gases. The confusion arose because neither hydrogen nor helium possesses easily detected spectral features in the visible spectrum. It was not until the Voyager spacecraft measured the far-infrared spectra of Jupiter and Saturn that a reliable abundance for the elusive helium could be found. The ... |
to get something into space to maintain the country’s prestige. However, the primary US satellite program, Vanguard, ran into difficulties: each of its early launches crashed or exploded. Simultaneously, a second team of rocket engineers and scientists had quietly been working on a military launch vehicle called Jupit... |
of work by Voyager Project, JPL, and NASA) Different gases freeze at different temperatures. At the temperatures and pressures of the upper atmospheres of Jupiter and Saturn, methane remains a gas, but ammonia can condense and freeze. (Similarly, water vapor condenses high in Earth’s atmosphere to produce clouds of ic... |
. As it descended to a pressure of 5 bars, the probe should have passed into a region of frozen water clouds, then below that into clouds of liquid water droplets, perhaps similar to the common clouds of the terrestrial troposphere. At least this is what scientists expected. But the probe saw no water clouds, and it me... |
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