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Exploration through Navigation Challenge
Challenge Questions

Challenge Question #1
Challenge Question #2
Challenge Question #3
Challenge Question #4
Challenge Question #5
Challenge Question #6

Question #1:

Astronomers measure the apparent size of celestial objects using degrees.
Just as a circle contains 360 degrees, you can see what one degree on the sky looks like by slicing the horizon into 360 slices.  
From Earth, the moon’s apparent diameter is half a degree. What is the apparent diameter of the Earth as seen from the moon?


Earth diameter = 12,756 km
moon diameter =  3,476 km
Ratio Earth/moon = 3.67
Apparent diameter of Earth as seen from the Moon = 0.5 degrees x 3.67 = 1.84 degrees

Congratulations! Our winner is from Bern Homeschool, Oakland California

Question #2:

Look at the moon and notice that there are two different kinds of terran: bright areas and dark areas. How are they different, besides their color? What are the compositions (rock types) of the bright and dark areas of the moon? What are the Latin words scientists use to refer to these areas, and what do they mean?


The bright areas are rugged highlands. The dark areas are relatively smooth lowlands. The bright areas are made of shattered and crushed rock called breccia (BREHCH ee uh); the dark areas are made of volcanic rock called basalt (ba SAWLT).  The Latin name for the highlands is terrae (TEH ree) which means “land.” The Latin name for the lowlands is maria (MAH ri uh), which means “seas” (because ancient astronomers thought they were literally seas filled with water).
Source: Spudis, Paul D. "Moon." World Book Online Reference Center. 2004. World Book, Inc.

Congratulations! To Ms. Stoica's 9F class for submitting the winning answer to Question #2

Question #3:

How old are the oldest rocks found on the moon?
How old are the oldest rocks found on the Earth?
Why don’t we find rock on the Earth as old as those on the moon?

Answer: The oldest rocks brought back by the Apollo astronauts are about 4.5 billion years old; this is just 100 million years younger than the time of the solar system’s formation 4.6 billion years ago. The oldest rocks found on Earth are about 4.0 billion years old—not because the Earth is any younger than the moon (in fact, it’s a bit older), but because the first half-billion years of Earth’s history has been erased by vigorous geologic activity, especially the restless shifting of the continents called plate tectonics. On the moon, where most geologic activity ceased around 3 billion years ago, rocks from the earliest 500 million years of its history are still preserved.

Congratulations! To Jacob and Kenny from Ms. Nelson's class for submitting the winning answer to Question #3

Question #4:

a. Why don’t we see the far side of the moon from Earth?
b. Explain the difference between the far side and the dark side.

a. The force of gravity exerted by a celestial body is stronger for objects that are closer to it, and weaker for objects that are farther away. In the case of the Earth and moon, the Earth's gravitational pull is slightly stronger on the side of the moon facing the Earth, and slightly weaker on the side of the moon facing away from the Earth. The imbalance creates a so-called tidal force that creates slight bulges in the moon's shape. Initially, the moon's rotation was faster than it is today, but over time, the gravitational pull on these bulges slowed the moon's rotation, until today, the moon rotates at the same rate as it's orbit around the Earth. (This process was also helped by the fact that the moon's center of mass is actually a bit closer to the near side than it is to the far side.) As a result, the moon always presents the same side to the Earth. We call the part of the moon facing away from the Earth the far side.

b. As the moon circles the Earth, making one rotation during each orbit, the sun shines on all portions of the moon. At any given moment, the side facing away from the Sun is called the dark side. This is not the same as the far side, which is sometimes in sunlight and sometimes in darkness.

Congratulations! Ms. Stoica's 9I class for submitting the winning answer to Question #4

Question #5

    Starting assumptions:
  • Assume it costs $100,000 to transport one pound (Earth weight) of supplies from Earth to a base on the surface of the moon.
  • Assume each astronaut requires 0.8 gallons of water on any day when that astronaut remains inside the base all day, and 1.2 gallons of water on any day when the astronaut goes outside for a seven-hour moonwalk, working inside a pressurized space suit.
  • Assume each astronaut does a moonwalk every other day (so that half the crew does a moonwalk one day, the other half does a moonwalk the following day, and so on). Questions:
  1.  For an early lunar expedition with 4 people staying on the lunar surface for 8 days, how much does it cost to carry enough water for the crew’s stay on the lunar surface?
  2. For a lunar base crew of 6 people, living on the moon for 180 days, how much does it cost to supply the base with enough water, carried from Earth, for that crew?
  3. To save the cost of transporting water from Earth, suggest one way that astronauts on the moon might obtain water locally, assuming there is NOT any ice buried under the surface.

    On any given day, half the crewmembers each use 0.8 gallons of water and the other crewmembers each use 1.2 gallons. If the total number of crewmembers is N, this becomes ((N/2) x 0.8) + ((N/2) x 1.2) = N gallons per day total for the entire crew.
  • For the 4 person crew, the total water usage per day is 4 gallons.
    For the entire 8-day lunar stay, the total water usage for the entire crew is 32 gallons.
    Multiplying by the weight of a gallon of water, 8.35 pounds (Earth weight), we get
    32 x 8.35 = 267.2 pounds (Earth weight).
    Multiplying by $100,000 per pound, we get a cost of $26,720,000

  • A six-person crew uses 6 gallons of water each day. Over 180 days the total usage is 1,080 gallons weighing 9,018 pounds (Earth weight). This translates to a cost of $901,800,000.

    One way to obtain water on the moon would be to combine oxygen and hydrogen obtained from lunar rocks and soil.
    Over billions of years hydrogen has been deposited in lunar soil as part of the steady stream of subatomic particles from the Sun called the solar wind. Releasing hydrogen can be accomplished by heating lunar soil to a temperature of 700 degrees Centigrade. (One way to create the necessary heat might be to focus sunlight with curved mirrors.)
    Oxygen, meanwhile, is contained in the mineral ilmenite, a titanium oxide that is present in lunar rocks (including tiny rock fragments mixed in with the soil). To release the oxygen, ilmenite is exposed to hydrogen and heated to a temperature above 800 degrees Centigrade. Once the oxygen is released, it can combine with the hydrogen to produce water.


Congratulations! to Rogers Home School for submitting the winning answer to Question #5

Question 6
    Starting assumptions:

  • Assume that the concentration of ice contained in the lunar soil within permanently shadowed craters is 2 percent by weight.
  • Assume that the ice exists only in the top 2 meters of soil.
  • Assume that the density of lunar soil is 2.9 grams per cubic centimeter (Earth weight).
  • Questions:
  1. Scientists have estimated that the total area of the moon that is permanently in shadow, at both north and south poles, is 12,500 square kilometers. Based on the above assumptions, how many gallons of water are contained in the lunar polar regions?
  2. Based on the information in Question 5, how many astronauts, living and working at bases on the moon, could this much water sustain for a year?
  3. Do you think it is realistic to harvest all this water? Suggest ways to help astronauts working at a base in the moon’s polar regions to obtain ice from lunar soil. Estimate how much water could be harvested in one year of base operations.

  1. -Multiplying the area of 12,500 km” times the thickness of 2 meters, we get a total
    volume of 25 km“ for the ice-rich layer.
    -At a density of 2.9 g/cm“ this gives a total weight of 72,500,000,000,000 kg (this can also be written as 7.25 x 10’“ kg) .
    -If the ice amounts to 2 percent of this value, that gives us 1,450,000,000,000 kg of ice.
    -Converting to pounds, we get 3,190,000,000,000 pounds of ice.
    -Dividing by 8.35 pounds per gallon, we get 382,035,928,144 gallons of water. (Of course, slight variations in the value you use for the number of pounds per gallon
    will produce slight variations in the answer.)

    Alternatively, we could calculate that 1,450,000,000,000 kg of ice is equal to
    1,450,000,000,000 liters of water; then, multiplying by 0.26 gallons per liter, we get:
    377,000,000,000 gallons.

    Either answer is acceptable.

  2. From Question 5, we know that the average water use for astronauts at a lunar base is 1 gallon per person per day. Therefore, one person uses 365 gallons of water
    per year.

    To find the number of people that could be supported by the total amount of ice on the moon, we divide the answer from (a) by 365 and we get 1.03 billion people.
    (Again, variations in this answer because of different methods of calculating (a) are acceptable.)

  3. Thanks for all the great ideas and comments!

Congratulations! Ms. Stoica's 7th Grade class for submitting the winning answer to Question #4

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Editor: Linda Conrad
NASA Official: Liza Coe
Last Updated: October 2008