Question

Instructions: Below are both crater images (some of the work is already done for you on the Southern image). At the bottom left you will see scale bars and a set of circles to help you do the actual counting. We have already identified craters that are 8 km across with red dots, so you only need to worry about craters greater than the outlined ones. Do not recount those craters that have already been marked with red dots. To use the circles in the images follow this procedure: 1) Click (left button on a Windows mouse) on the image, you will notice the entire image will be selected (Little handles will appear on the edge). 2) A second click on a circle will select the circle and you will then be able to move it. 3) Move circle above crater of the proper size range. In the example at right, the crater is more than 32km but less than 64 km in diameter; it is therefore in the 32-64 km category (red circle). The picture at right has a 32km green circle to illustrate that the green circle is smaller than the crater and therefore not correct. 4) While the circle is still selected, (it still has the little handles for rescaling and moving on it), press CRTL +D (hold control key and press D). This will generate a second circle of the same size near the first one. Move the second circle to another crater and generate the next circle with CTRL+D again. Move across the image systematically until all craters of that size are filled. Probably best to count whilst doing it. Use the provided circles to count the craters. (If something goes horribly wrong, or you delete circles, check the Crater counting in Word pdf which explains the procedure in more detail) Notes: Please be careful not to count a crater and then again count the ejecta blanket (see modules for information on ejecta blankets). The forums are the best place to ask questions, please make use of them. Crater counting takes time, but it can be relaxing. Steady work is more effective than rushed work and your answers depend on the quality of your counts. Even with the ranges we accept, very poor counting will lose you marks on later questions. Recommended music for crater counting is Gustav Holst's Jupiter, Bringer of Jollity (or the whole The Planets suite)

Answer 1

Page No. Date 12 Difference between two marhias Hemispheres.- Cvorthen hemisphere gurtace age 3.7-4.0 billion yerys ago average age of this is = 3.85 billion years ago. Seuthern hemisphese gustace age = 4.0-4.4 billion year ago Average age 4.2 billion years ago. So geed substract younger From older, Se southern Hemisphere surface age (Ver thern Hemisphere suntace age 4.2- 3.85 0.35 billion of this is years. years. 13. So the age difference is a 0.35 billion Percentage that has the cratering in that cloze decreased in the younger hemixphere, compared to the older hemigphere Younger Actual crater count older actual crales count For 16-32 km Actual craler count in Northers Cyounger) Hemisphose Actual crater count in southern Colder) X 100 Hemisphere = 26 6 26 x 100 = 23%