The marks they leave behind are the same as those found in ancient rocks in South Korea.

它们留下的印记和在韩国发现的古老岩石中的印记一模一样。

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Now they have discovered that the ancient rocks on Mars and in Australia share many similar minerals.

现在，他们在火星和澳大利亚的远古岩石群中均发现很多类似的矿物质。

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To help resolve this discrepancy, scientists investigated ancient rocks from Isua, Greenland, to see how the planet changed over time and when precious metals entered the picture.

为了解开这个矛盾，科学家们研究了格陵兰岛伊苏瓦(isua)地区的古老岩石，去观察地球是怎样随着时间而变化的，以及在什么时候贵重金属进入地球。

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To get below the ancient lunar rocks, NASA crashed a rocket into the moon's south pole.

VOA: special.2009.12.30

A one-hour trip in a small airplane makes it possible to see the park's red rocks, arches and flat areas where ancient Indian people once lived.

VOA: special.2009.04.15

Yet, some of the most promising locations to search for ancient life on Mars are places where water may have been in contact with volcanic rocks, ancient hydrothermal systems where conditions may have been conducive to life.

CNN: How the search for aliens can help sustain life on Earth

Rocks initially formed as layers of sediment laid down in an ancient sea can be deciphered by knowing that older layers are found beneath the younger layers.

BBC: Mars south pole

The twin landers, each the size of a desk and weighing 375 pounds (170 kilograms), will ramble dozens of meters a day, drilling into rocks and scooping up soil in preliminary field studies to help identify ancient oases.

CNN: Race to Mars begins a distant search for life