Scientists are considering the possibility of sending humans to Mars in the coming decades. Although there have been successful manned missions to the Moon in the 1960s and 1970s, Mars is 150 times further away from Earth than the Moon is. Thus the project of sending humans to Mars would require solving an array of problems the Moon missions did not have to face. One problem is that a round-trip to Mars and back is likely to take at least two years. The trip to the Moon lasted only a few days, and it was easy to bring enough supplies of food, water, and oxygen; but the cargo capacity of space vehicles is too limited to put on board the food, water, and oxygen required by a crew for a period of two years. Without those essentials, though, a Mars mission is impossible. A second problem is that astronauts on the Mars mission would be in the zero-gravity environment of space for many months at a time. Spending a long time in the zero-gravity environment has negative effects on the human body, such as decreased muscle mass and lower bone density. Over the course of a two-year mission, the effects would be so severe, they would make it impossible for humans to make the trip without experiencing grave medical problems. Finally, astronauts on a mission to Mars would be exposed to dangerous levels of space radiation, much of which comes in the form of charged particles emitted by the Sun. Earth’s magnetic field, which normally protects us from dangerous solar radiation, would not be able to protect a spaceship traveling in interplanetary space. Constructing a shield that would protect the whole spaceship from space radiation is at present impossible because it would add too much weight to the ship.
Summarize the points made in the lecture, being sure to explain how they respond to the specific concerns presented in the reading passage.
In the lecture, the professor casts doubt on the reading passage’s idea that a manned mission to Mars would be impossible due to challenges related to supplies, zero gravity, and solar radiation. The professor asserts that scientists have proposed viable solutions to each of these issues.
Firstly, the passage claims that a round trip to Mars would take at least two years, and space vehicles lack the cargo capacity to store enough food, water, and oxygen for the crew. By contrast, the professor asserts that astronauts could use hydroponics, a method of growing plants in water instead of soil. This technique requires little space and would allow astronauts to cultivate their own food. Additionally, hydroponically grown plants would recycle wastewater into clean drinking water and produce oxygen, ensuring a sustainable supply of essential resources.
Secondly, the author of the passage points out that prolonged exposure to zero gravity would cause severe health issues, such as muscle loss and reduced bone density, making long-duration space travel dangerous. However, the lecture notes that astronauts on space stations have already learned to manage these effects through regular exercise and by taking vitamins and minerals like calcium, which slow down bone density loss. These techniques would help astronauts maintain their health during a Mars mission.
Lastly, the reading states that astronauts would be exposed to dangerous levels of solar radiation, and constructing a protective shield for the entire spacecraft would be impractical due to weight concerns. On the contrary, the professor contends that the Sun only releases dangerous radiation intermittently. The spacecraft could be equipped with instruments to monitor solar activity and a small, lightweight shielded shelter. Astronauts would stay in the unshielded areas under normal conditions and move to the shielded shelter only during periods of high radiation.
会员福利内容准备中，丰富答题思路即将上线