Crater Counting
Homework 1_Meteorites and Impact Craters
Julia KahmannRobinson PhD and Marjorie Chan PhD, University of Utah Department of Geology & Geophysics
Background
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In reference to: http://www.msss.com/http/ps/age2.html
 On Earth we often use radiometric dating to date the age of Earth's rocks, on Mars is this technique applicable? Why or why not?
 What is the general implication of age relative to the overall appearance of craters?
 How can we roughly divide the history of crater formation into three periods, from oldest to newest (list size of crater and corresponding Mars Epoch with age constraints):
 Using the map of Mars in Figure 1, sketch the basic boundaries of the three Mars Epochs that are based on crater counts (Labels: Noachian, Hesperian, Amazonis)
Crater Counting
Measure the diameter of as many craters you can using JMARS Crater Counting layer. Choose craters that are roughly the same size. Use a 128 zoom OR larger (to give you at least 30 or more craters) and fill in the average crater diameter and # of craters you measured (128 zoom will give you at least a 100km^{2} view). If you can separate out sizes, do so.
Region 
Size 1: Ave d/# 
Size 2: Ave d/# 
Size 3: Ave d/# 
Amenthes Rupes




Vichada Valles




Mawrth Valles




Astapus Colles




 Using the isochron diagram in Figure 2, plot your craters and determine the age of the terrain. Make sure to scale the Yaxis correctly (To scale correctly: use proportions and be sure to square the area you investigated.)
 Example: 20 counted craters, diameter 4km in a 200km^{2} counted area20/ (200)^{2} = 0.0005 which gives you a yaxis value of 10^{5} use the diameter of 4km that you measured for the xaxis and plot.
 Amenthes Rupes Epoch: _______________________
 Vichada Valles Epoch: _______________________
 Mawrth Valles Epoch: _______________________
 Astapus Colles Epoch: _______________________
 Does your age coincide with the sketch you made in #4?
 What are the difficulties you faced in crater counting on Mars? Do you feel like it is far too "averaged" and some terrain are not accounted for? Why or why not.
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