Home of the Future
While no human being has walked on the moon since the last Apollo mission in 1972, NASA and many international agencies are contemplating a return. But these missions will not be sending astronauts to the lunar surface empty-handed; future visits have the goal of establishing a permanent colony on the moon. A majority of the estimated 20 billion tons of water available at the lunar poles would likely be broken down into raw materials—hydrogen and oxygen—in order to manufacture rocket fuel. Scientists want to one day be able to use the moon as an economical fueling station.
Current projections estimate that a small, semipermanent settlement on the moon could be completed by the late 2030s, and scientists have already developed many practical solutions for surviving in the harsh lunar environment. Without an atmosphere, the surface of the moon is unshielded from cosmic and solar radiation and experiences extreme temperature fluctuations from 121 degrees Celsius during the day to negative 157 degrees at night. Habitation will also need to provide protection from meteorites and to filter particles from the toxic lunar soil out of the air supply. One solution for moon habitats is to build them underground in lava tubes. Living quarters on the surface could be covered with moon rock. Engineers are working on a process that could convert the soil into bricks by using concentrated sunlight to change the soil into a solid building material.
Which of the following sentences would be the most effective conclusion to the passage?
Answer choices for the above question
A. These problems may seem unsurmountable, but scientists have decades to solve them.
B. Once these problems are solved, the first step toward humans establishing a colony on Mars will have been taken.
C. Scientists will continue to find ways to place a lunar colony, and everything that lies beyond it, within our grasp.
D. For every challenge that stands in the way of someday living on the moon, the only real barriers are cost and time.
