TERRESTRIAL PLANETS

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saturnbutton1.JPG (21728 bytes)Mars - Interior

saturnbutton1.JPG (21728 bytes)Mars - Surface

saturnbutton1.JPG (21728 bytes)Mars - Atmosphere

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saturnbutton1.JPG (21728 bytes)Mars - Interior Questions

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Q1.  Why do we suspect that Mars has a small core? Explain your reasoning. Answer

 

 

 




















 

saturnbutton1.JPG (21728 bytes)Mars - Atmosphere Questions

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Q1.  Mars is frequently engulfed in global dust storms. Why do these storms occur? Answer

Q2.  Why is Mars’ atmosphere so thin today, compared to Earth’s? Answer

Q3.  Why are there large seasonal changes in the atmospheric pressure on Mars? Answer

Q4.  Describe the evolution of Mars atmosphere over time.  Answer

Q5.  Why is Mars’ atmosphere so very thin today? What evidence from surface features is there that Mars once had a dense atmosphere? Answer

 

 




















 

saturnbutton1.JPG (21728 bytes)Mars - Surface Questions

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Q1.  Part of Mars’ surface is relatively young, while the other part is much older. How do we know? Why or how did this occur? Answer

Q2.  Mars has many volcanoes? How do we know they are all extinct? Why are they so much larger than those found on Earth? Answer

Q3.  What evidence is there that liquid water once existed on the surface of Mars? What had to be different about Mars in the past for liquid water to exist on the surface? Answer

Q4.  What evidence is there at erosion has occurred on Mars? Why would we not expect it to continue today? Answer

Q5.  What evidence is there that there has been no plate tectonic activity on Mars? What caused the huge canyon system on Mars? Answer

Q6.  In what two ways are craters on Mars different from those on the Moon? Answer

Q7.  Why are volcanoes on Mars so much larger than any on Earth? Answer

Q8.  Describe the composition of Mars’ ice caps. What effect does their formation each winter have on the rest of Mars? Answer

Q9.  Describe the two types of dry river channels on Mars. How do we believe they occurred? Answer

Q10.  Give a general description of the surface appearance of Mars. Answer

 

 




















 

 

 

saturnbutton1.JPG (21728 bytes)Mars - Interior Answers

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A1.  Since the average density of Mars is only slightly greater than the average density of a typical rock (3.8 for Mars versus about 3 for a typical rock), it could not have a significant core of dense material without raising its overall density to a higher value.

 

 




















 

 

saturnbutton1.JPG (21728 bytes)Mars - Atmosphere Answers

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A1.  In the winter on Mars, a significant fraction of the atmosphere condenses onto the polar ice cap. The resulting low pressure over the pole causes a strong wind as air moves from the opposite pole (where summer heat is causing that ice cap the evaporate). These winds moving from one polar cap to the other cause global dust storms.

A2.  A terrestrial planet’s atmosphere is released by volcanoes. In the case of Mars, its gravity is not strong enough to permanently retain an atmosphere. When the volcanoes became extinct, the atmosphere continues to leak away but no new gases were released to replace those that were lost.

A3.  Mars is far enough from the Sun and cold enough for CO2 to condense into ice during the Martian winter. So much condenses that the atmospheric pressure changes appreciably. Correspondingly, when the ice cap sublimes in the summer the atmospheric pressure increases dramatically.

A4.  Mars once had a dense, warm, humid atmosphere. While volcanoes were active, new gasses were released to replace those lost from the atmosphere due to the weak gravity or which condensed on the surface. When the volcanoes died, that replacement mechanism was lost. Water was gradually lost by the process outlined in the previous question and as permafrost in the soil. The weak gravity of the planet was unable to hold onto the atmosphere, which slowly evaporated from the planet.

A5.  Mars is a small planet with weak gravity. Its atmosphere slowly leaks away to space. Now that all of its volcanoes are extinct, there is no source of new gas to resupply what has left. Dry river channels visible on the surface indicate that Mars’ climate was once warmer than today. If its atmosphere had always been as thin as we see today, liquid water could not have flowed on the surface.

 

 




















 

 

saturnbutton1.JPG (21728 bytes)Mars - Surface Answers

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A1.  We can tell that the northern half of Mars is relatively young because there are very few impact craters there, compared to the southern half of the planet. The surface of the northern hemisphere of Mars has been covered relatively recently by volcanic outflows from the many volcanoes found there.

A2.  We can tell that all the volcanoes of Mars are extinct because all of them have impact craters on their flanks. If there had been recently active, at least a few of them would not have impact craters on them. They become large, compared to Earth’s volcanoes, because there is no plate tectonics on Mars. A volcano on Earth is constantly "cut off" as the crust moves past a single hot spot in the mantle. Instead of single large volcano, plate tectonics on Earth produces a chain of smaller volcanoes.

A3.  Dry river channels on Mars’ surface suggest that liquid water once existed there. However, the present atmosphere of Mars would not allow liquid water to exist on the surface. The atmosphere is so thin that water would evaporate very quickly from the surface. The existence of dry river channels on Mars suggests that the atmosphere must have been much denser in the past.

A4.  The most obvious evidence of erosion on Mars are the dry river beds at various places. It is also possible that the dust storms may produce a very mild erosion. The liquid erosion is not possible today on Mars because the atmosphere is too thin to allow liquid water to exist on the surface.

A5.  The volcanoes on Mars are very large, compared to a typical terrestrial volcano, which indicates that the crust did not move during the formation of the large volcanoes. However, there is evidence of vertical motion or swelling associated with volcanoes. As one region expanded, adjacent regions cracked from the stress created by the uplift. These cracks are visible as a huge canyon system on Mars that stretches for thousands of miles.

A6.  The ejecta of some craters on Mars shows evidence of fluid flow instead of explosive ejection. This suggests that permafrost in surface layers on Mars melted at impact and the water carried loose particles away from the crater. Some craters on Mars also show the effects of erosion, as blowing dust fills them in. Neither of these phenomena are seen on the Moon.

A7.  Since there is no plate tectonics on Mars, a volcanic vent remains in one location and builds a single volcanic mountain. On Earth, several mountains can be made by a single vent as crustal plates move over it. This plate motion prevents any one volcanic mountain from getting very large on Earth.

A8.  Mars’ ice caps are made of a combination of water ice and carbon dioxide ice (dry ice). So much dry ice condenses each winter to reduce the air pressure over the pole by as much as 20 %. The pressure difference between the poles (one freezing while the other "melts") causes a condensation flow of air from one pole to the other.

A9.   Some river channels on Mars show many tributaries in a highly developed system of channels, reminiscent of young river systems on Earth. Other channels are huge outflow channels which seem to have been carved by single, massive floods. In both cases, we believe that the flow of water occurred when permafrost was melted (perhaps by impacts or volcanism) and reached the surface in springs.

A10.  Mars is heavily cratered in the southern hemisphere and heavily volcanic in the northern hemisphere. One major volcanic highland is known as the Thasis bulge, which cause a long fracture canyon on its edge. Dry river channels are found, along with extensive evidence of dust erosion. Polar caps form at each pole during the winter.