地球上的最后生物将是微生物 computer, 微生物, 地球

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The last surviving creatures on Earth will be tiny organisms living deep underground, according to scientists.

科学家认为，地球上最后生存的生物将是生活在地下深处的微生物，因为随着太阳变得越来越热，越来越亮，只有细菌才能在这种极端条件下苟延残喘。

Researchers used a computer model to assess our planet's fate billions of years from now.

They found that as the Sun becomes hotter and brighter, only microbes would be able cope with the extreme conditions that the solar changes would bring.

The research is being presented at the National Astronomy Meeting.

Jack O'Malley James, from the University of St Andrews in Scotland, said: "There won't be very much oxygen present, so they need to be able to survive in low or zero-oxygen environments, high pressures, and high salinities because of evaporating oceans."

Mass extinction

The future of life on Earth is tied to that of the Sun, and over time, our star will become more and moreluminous（明亮的）.

Scientists from the universities of St Andrews, Dundee and Edinburgh used this fact to create a forecast for our planet's future environment.

In a billion years' time, the heat from the Sun will become so intense, that the oceans start to evaporate.

"Once you get to this tipping point, you get a lot more water in the atmosphere and because water vapour is a greenhouse gas, that sets this runaway greenhouse effect... and you end up with the Earth heating up to 100C or more plus what we experience today," explained Mr O'Malley James, a PhD student.

This, he said, combined with falling levels of oxygen, would lead to the rapid loss of plants and larger animals.

Soon after, a group of microbes called
extremophiles（极端微生物）
would be the only life forms left.

These tiny organisms are found on Earth today, and can cope with hostile environments.

These, the scientists said, would be the only creatures that could withstand the heat, aridity and poisonous atmosphere of this future Earth. They believe that they would probably be clustered around the last drops of water deep underground.


Eventually as conditions worsen they too will vanish, and in about 2.8 billion years, Earth will be devoid of all life.
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