Scientists and engineers     1     (prepare) for possible travel into interstellar space, the area in between stars, in the distant future. Experts believe it will likely take many years before the technology and equipment are developed     2     (send) humans to this unexplored area of space. But if it does happen, massive spaceships     3     carry humans on long trips to distant stars.

Two American researchers, Andrew McKenzie from the University of Kansas and Jeffrey Punske of Southern Illinois University, have explored one possible problem with such travel. They considered the possibility    4     changes in human language could develop over time, thus    5    (cause) major communication problems with people on Earth.

Languages naturally changes as communities grow more isolated from each other, the researchers noted in the paper. The long isolation of a community could lead to enough differences in language to make    6    impossible for community members back home to understand.

The researchers noted that in addition to new words being used, the language of people traveling on spaceships and living in colonies    7     (experience) many other changes. For example, the sounds of different letters would likely change over time, affecting not only individual words, but the whole grammatical system.

The researchers say one possible solution to    8    (limit) communication problems would be to include language experts on spaceship crews. Another suggestion is to use sign language as a form of communication. McKenzie added that space travelers might question whether it is even worth trying to learn how to communicate with people on Earth. But he believes there will always be a need, even    9    it is very limited. “You have to learn a little Earth English to send messages back, or to read the instruction manuals and information    10    came with the ship,” he said.

There is no doubt that humankind dreams of making Mars our second home. However, sending people there will require all the skills, courage and     1     (intelligent) of the human race. While the Moon can be reached within days, it would take months to reach Mars,     2     (travel) through dangerous solar radiation. And even if the first settlers do reach Mars safely, staying alive will be     3    daily challenge, but as proved by the Biosphere experiment, not impossible.

As early as the 1980s, scientists were building Biosphere 2 in the Arizona desert. It consisted of a closed space    4     people, animals and plants could live together. The “closed” concept meant that the space was designed     5     (function) with its own oxygen, food and water, needing nothing from the outside world.     6     the two-year experiment was not a success, it did provide us with a better understanding of how humans might be able to live on another planet. More recently, scientists     7     (succeed) in growing a variety of plants in an environment similar to that on Mars. That     8     (definite) is a big step forward.