.....green plants ultimately. When it first appeared therefore, it would have been seen as a poison, it would have been a pollutant. But gradually, through Darwinian natural selection, living organisms have become more and more used to oxygen. They've been selected to thrive in the presence of oxygen, so that now, most living organisms can't live without oxygen.

Green plants can trap the sun's energy to produce not just the oxygen we breathe, but the food that supports the entire animal kingdom. The other great lifegiver on earth is water. Our water rich world is an oasis for life. Earth's sister planet Venus may also once have had water, but soaring temperatures caused by a runaway greenhouse effect had made it a hostile environment to living things.

Venus and earth had roughly similar potential for developing into life-supporting planets. But, only earth succeeded. At Lulworth Cove in England, Ellen Stophan is trying to figure out why.

This rock is Jurassic limestone that was formed over about a hundred million years ago in shallow seas. This rock is made mostly of carbonates, it has a lot of carbon dioxide in it. On Venus, most of the carbon dioxide is actually in the atmosphere. On earth, it's tied up in limestones like these that were formed in the Jurassic. Why did Venus end up with all its carbon dioxide in the atmosphere and earth with it tied up in big rocks like this is a question that we are puzzling with right now. We think it might have to do with something with the evolution of life on earth. Maybe the earth was just far enough away from the sun that it was cool enough that it allowed life to evolve, took that carbon dioxide out of the atmosphere. On Venus, all the carbon dioxide remained in the atmosphere, and we ended up with a planet that's baking on in its own heat.

When the sun sets, Venus is often the brightest object in the sky, outshining the night lights of Tucson, Arizona. It twinkles like a star because the planet's dense cloud cover is extremely reflective.

In 1967, Venera IV became the first space probe to penetrate the Venusian clouds and transmit data. The first probe to softland on the surface and send back information was Venera VII in December 1970. The Venera landers only transmitted data for about an hour before being destroyed by the planet's intense heat and pressure. In August 1990, the Magellan Mission began a radar survey of Venus, which allowed imaging experts of the Jet Propulsion Lab to create this simulation of the Venusian landscape.

No traces of life were found. But, scientists were delighted to become more closely acquainted with our neighbor planet.

Looking at Venus through a telescope is, it's magical, because, you know, it is the evening or morning star,and you know, seeing it as a planet itself is kind of exciting. But at the same time, since it's totally covered by a set of dense clouds one would like to see more, and, so , with....

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words in this passage:

lifegiver:给予活力之人[事, 物]

runaway: out of control. 失去控制的
[sometimes it may mean surprisingly big. eg:Her first novel's runaway (= surprisingly big) success came as a great surprise.]

cove:a curved part of a coast which partly encloses an area of water; a small bay山凹, 小湾

Jurassic:[地质]侏罗纪的, 侏罗系的

Tucson:图森[美国亚利桑那州南部城市]

Jet Propulsion Lab:简称JPL， 喷气推进实验所[美]