First, even though the reading passage suggests that round-trip to Mars needs enough supplies of food, water, and oxygen since it will take at least two years, the professor argues that astronauts can use hydroponics, the way to cultivate plants without soil, to to solve this problem. This is because by growing crops, astronauts maintain their food supplies. Besides, such kind of eco-system can provide them with drinking water and oxygen. Obviously, the professor's argument disproves its counterpart in the reading.
Moreover, despite the statement in the reading that astronauts will suffer from negative effect in the zero-gravity environment of space during the two-year mission, the professor contends that this condition can be changed. She supports this point with the fact that exercising and replenishing vitamin can relieve such suffering.
Finally, the professor asserts that the threat of space radiation can be controled whereas the author of the reading claims that astronauts would definately be harmed by it. The professor suggests that astronauts only face the solar radiation occasionally and that they can hide in the shielder when it occurs.
In conclusion, the professor clearly identified the weakness in the reading passage and convincingly shows that the problems mentioned in the reading can be solved.
