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Example Question #101 : Earth And Space Sciences
Scientists have long debated the origin of organic molecules on Earth. Organic molecules are those based on the atom carbon, which can form four distinct bonds in contrast to the fewer number allowed in most other non-metals. As a result of this property, carbon can give rise to the enormously complex molecular shapes necessary for life to arise.
Some scientists argue that organic matter was dissolved in water ice on comets, and brought to Earth early in its history. These comets crashed into the early Earth, and deposited carbon-based molecules in copious quantities to the Earth’s surface as their water melted.
In 2014, the first space probe landed on the comet 67P/Churyumov-Gerasimenko. Suppose that scientists find the following information from 5 distinct samples after landing on the comet. Each sample was taken at a single geographical location, but 5 meters deeper than the last. Sample 1 was taken at a depth of 1 meter below the surface.
Sample # |
Water Ice? |
Concentration of Organics |
1 |
No |
N/A |
2 |
Yes |
1 mg/L |
3 |
No |
N/A |
4 |
Yes |
4 mg/L |
5 |
Yes |
10 mg/L |
These samples were compared to 5 similar samples from the surface of Mars. Scientists posited that this comparison would be meaningful because we know that life does not exist on Mars the same way that it does on Earth. Thus, they are comparing a known non-biological celestial body, Mars, with another celestial body, the comet, which may be seeding life on suitable plants.
Sample # |
Water Ice? |
Concentration of Organics |
1 |
No |
N/A |
2 |
No |
N/A |
3 |
No |
N/A |
4 |
No |
N/A |
5 |
Yes |
1 mg/L |
How far below the surface of the comet was the third sample measured?
10 meters
12 meters
11 meters
15 metes
11 meters
The passage indicates that the samples are taken 5 meters below the sample above them. The first sample was taken at 1 meter below the surface, the second was taken at 6 meters below the surface, and the third was taken at 11 meters below the surface.
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