Assignment task:
(1) Life is the reason that Mars is interesting to us: we search for the possibility of life early in that planet's history and try to determine the potential of Mars as a home for life in the future. Ultimately, perhaps, the Martian surface could support a planetary-scale biosphere.
(2) The near-term robotic exploration of Mars is the first step toward realizing this vision. Robotic probes provide us with background information about Mars: where to search for evidence of past and present life and how to assess the future biological potential of the planet.
(3) One important way to assess the biological potential of Mars is to send life there. Thus, a goal for the near-term robotic program ought to be to send a seed to Mars and to grow it into a plant-ideally a flowering plant-using to the extent possible the sunlight, soil and nutrients available in the Martian environment.
(4) Why do such an experiment if the laws of physics and chemistry are the same on another planet? Isn't testing on Earth adequate? Certainly, testing on Earth is important, but we gain technical as well as psychological reassurance by demonstrating viability on Mars.
(5) NASA has a long tradition of flying technology demonstration missions. Mars Pathfinder was such a mission. On a future lander mission, NASA plans to fly a unit to test oxygen production from atmospheric carbon dioxide on Mars. A module capable of growing a single plant from seed would also be a demonstration mission.
(6) The best design for a plant growth module for Mars would make use of the Martian soil, with nutrients added as necessary. Carbon dioxide and water would be obtained from the Martian atmosphere, and the natural sunlight on Mars would provide for photosynthesis. * Because of the lower pressure on Mars, the plant would need to be in a small pressure vessel-its own little spacesuit. The design of this miniature greenhouse would allow light to enter and, true to its name, provide greenhouse warmth during the day. At night the growth module may need to draw on heat generated by the main spacecraft to keep the plant warm. The plant's growth and flowering would be monitored using the lander camera. Initial designs by groups at the University of Colorado and the Jet Propulsion Laboratory have shown that such a unit can be constructed. We could therefore send life to Mars on the next lander.
(7) There are many reasons for sending a flower to Mars. First, it would be highly symbolic. This plant would be the first organism from Earth to play out its existence on another world. It would be a true biological pioneer, an important step for life on Earth expanding to other planets. More practically, a plant growth module would directly test the toxicity of the Martian soil. It would also demonstrate the effectiveness of Martian carbon dioxide and water for a Martian greenhouse. These are essential steps toward a full-scale greenhouse to support a human base. Moreover, the growth of a plant in the Martian environment would help alleviate concerns about the danger of contaminating the Earth by the return of Martian samples.
(8) In all these respects a plant growth model would serve as a biological precursor to human exploration. Indeed, when humans go to Mars, it would make sense for them to arrive at a site that has already established a biologically based life support system, tested and fully operating-robotically. As on Earth, we humans function best when surrounded by other life-forms.
(9) A simple plant growth module would not be in violation of the planetary protection policy. NASA abides by the policy established in 1967 to prevent the inadvertent contamination of Mars by terrestrial microorganisms. For the Viking missions this involved the complete sterilization of the spacecraft. However, these missions showed that environmental conditions on the surface of Mars were hostile to life. No organism known could grow or reproduce under Martian conditions. As a result, the requirement for sterilization was replaced with a limitation on the number of microorganisms on spacecraft surfaces to less than 300 per square meter.
(10) The original purpose of the planetary protection policy was to preserve extraterrestrial environments as objects of scientific study. We appreciate that the accidental contamination of an alien ecosystem has ethical implications that extend beyond scientific exploration. Sending life beyond the Earth is an important step and not one we would want to take without consideration of consequences.
(11) The planetary protection guidelines do not explicitly prevent the controlled transport of biological materials to Mars or the use of biological materials in controlled experiments aboard spacecraft. A plant growth unit could be constructed in accordance with the bioload limits of the present planetary protection policy. In fact, to be sure it functions as intended, the system might well exceed these limits and even be treated to eliminate nearly all bacteria.
(12) By developing ways to send life to Mars consistent with the goals of the planetary protection policy, a near-term plant experiment would pave the way for future research and study on the planet. Most important, the growth of a single flower on Mars would be a powerful symbol of the long-term goal of expanding life beyond the Earth, first to Mars and then elsewhere. It would rival the image of the Earth from space-the pale blue dot-as a symbol of our place and future in the universe.
Christopher P. McKay, "Flowers for Mars," excerpted from White and Billings, The Well-Crafted Argument, Boston: Houghton Mifflin, 2002, 393-395. Planetary Report, Sept./Oct. 2000. Used by permission of the Planetary Society.
1. What is the topic of this essay?
a sending a flower to Mars
b Mars
c growing plants
d life on other planets
A ". . . [A] goal for the near-term robotic program ought to be to send a seed to Mars and to grow it into a plant-ideally a flowering plant-using to the extent possible the sunlight, soil and nutrients available in the Martian environment." (paragraph 3)
B "Robotic probes provide us with background information about Mars. . . ." (para- graph 2)
C "NASA has a long tradition of flying technology demonstration missions." (para- graph 5)
D "We appreciate that the accidental contamination of an alien ecosystem has ethical implications that extend beyond scientific exploration." (paragraph 10)
2. What pattern organizes the supporting details in paragraph 7?
A series
B time order
C comparison/contrast
D cause/effect
3. Which of the following sentences includes a cause/effect transition?
A "As a result, the requirement for sterilization was replaced with a limitation on the number of microorganisms on spacecraft surfaces to less than 300 per square meter." (paragraph 9)
B "Moreover, the growth of a plant in the Martian environment would help alleviate concerns about the danger of contaminating the Earth by the return of Martian samples." (paragraph 7)
C "However, these missions showed that environmental conditions on the surface of Mars were hostile to life." (paragraph 9)
D "Most important, the growth of a single flower on Mars would be a powerful symbol of the long-term goal of expanding life beyond the Earth, first to Mars and then elsewhere." (paragraph 12)
4. What can you infer from paragraph 6?
A It's very cold on Mars at night.
B A plant on Mars would not need carbon dioxide to grow.
C Astronauts would have to go to Mars to check on the plant's progress.
D Sunflowers would probably grow well on Mars.
5. What is the implied main idea of paragraph 6?
A The conditions on Mars would allow a plant to grow if it were enclosed in a special greenhouse module.
B The University of Colorado's design for a plant growth module is better than the designs of any other group.
C Growing plants is a fun and rewarding hobby.
D Mars is the only other planet besides Earth where plants can grow.
6. What is the author's tone in this selection?
A serious
B amused
C angry
D sad
7. Which of the following sentences states a fact?
A "The original purpose of the planetary protection policy was to preserve extraterrestrial environments as objects of scientific study." (paragraph 10)
B "Thus, a goal for the near-term robotic program ought to be to send a seed to Mars and to grow it into a plant-ideally a flowering plant-using to the extent possible the sunlight, soil and nutrients available in the Martian environment." (paragraph 3)
C "The best design for a plant growth module for Mars would make use of the Martian soil, with nutrients added as necessary." (paragraph 6)
D "Sending life beyond the Earth is an important step and not one we would want to take without consideration of consequences." (paragraph 10)
8. Which of the following sentences does not offer a major supporting detail in paragraph 7?
A "It would be a true biological pioneer, an important step for life on Earth expanding to other planets."
B "More practically, a plant growth module would directly test the toxicity of the Martian soil."
C "It would also demonstrate the effectiveness of Martian carbon dioxide and water for a Martian greenhouse."
D "Moreover, the growth of a plant in the Martian environment would help alleviate concerns about the danger of contaminating the Earth by the return of Martian samples."
9. What can you infer from this selection about the author's proposal?
A He wants to send a flower seed to Mars in a robotic probe.
B He wants to send humans to Mars to try to grow flowers.
C He does not believe a plant can grow on Mars.
D He wants astronauts to explore Mars to search for flowering plants.