[A] agreeable [B] characteristics [C] collected [D] confirms [E] confronted

[F] encountered [G] especially [H] harsh [I] implies [J] ingredients

[K] occasionally [L] periodically [M] presence [N] seasonal [O] substance

The journal Science reported a new study about the definitive evidence of organic matter on the surface of Mars.

The data was【C1】_____by NASA’s nuclear-powered rover Curiosity. It【C2】__earlier findings that the Red Planet once contained carbon-based compounds. These compounds—also called organic molecules (分子)—are essential【C3】__for life as scientists understand it. The organic molecules were found in Mars’s Gale Crater, a large area that may have been a freshwater lake over three billion years ago. The rover【C4】__traces of the molecule in rocks extracted from the area. The rocks also contain sulfur, which scientists speculate helped preserve the organics even when the rocks were exposed to the【C5】_____radiation on the surface of the planet.

Scientists are quick to state that the【C6】_____of these organic molecules is not sufficient evidence for ancient life on Mars, as the molecules could have been formed by non-living processes. But it’s still one of the most astonishing discoveries, which could lead to future revelations,【C7】_____when one considers the other startling findings that Curiosity uncovered around five years ago.

The rover analyses the air around it【C8】_____, and in 2014 it found the air contained another of the most basic organic molecules and a key factor of natural gas: methane. One of the【C9】__of methane is that it only survives a few hundred years. This means that something, somewhere on Mars, is replenishing (补充) the supply. According to NASA, Mars emits thousands of tons of methane at a time. The level of methane rises and falls at 【C10】_____intervals in the year, almost as if the planet is breathing it.

【C10】