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	<question>
		<phrase isaudiomp3="1" mp3="AUDIO_REPOS/1.0.mp3"></phrase>
		<question isaudiomp3="1" rationale="0" picture="images/question1.jpg" mp3="AUDIO_REPOS/2063-1" exercise_type="" questionmode="" choicemode="" answerbankid="" answerbankmode="" rationalemode="" playonload="" mp3speed="" ttsspeed="" passage="1" show_passage="" show_passage_audioplayer="" passage_audio_type="" showvideo="" video="" enable_audio_recorder="" recorder_mode=""><![CDATA[]]></question>
		<saythis><![CDATA[]]></saythis>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[LOS ANGELES  -  Planetary scientists dream of sending a geologist to Mars to study its rocks by hand.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[Until then, they have to settle for examining meteorites  -  chunks of the Red Planet that land on Earth after hurtling through space and surviving the searing fall through our atmosphere.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[Though a little banged up, these meteorites provide a vital up-close view of our rust-hued neighbor.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[But it can be hard for geologists to interpret what they see when they can't agree on how old a rock is.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[Conflicting age estimates for certain rocks differ by up to 4 billion years  -  the vast majority of Mars' planetary existence.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[In a paper last month in the journal Nature, an international team of scientists sought to sort this out for a particular group of meteorites known as shergottites.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[Martian space rocks tend to be very old, but shergottites are thought to be remarkably young.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[Most scientists believe the shergottites were formed as a result of volcanic activity about 150 to 250 million years ago.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[This would place their formation during Earth's Jurassic period, when dinosaurs roamed the Earth.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[If so, shergottites are a sign that Mars might have been geologically active fairly recently.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[That in turn means it might still have been hospitable to some form of life, said Munir Humayun, a planetary geochemist at Florida State University who was not involved in the study.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[But a few researchers recently estimated that shergottites are actually about 4 billion years old  -  a finding that had far-reaching implications for scientists' understanding of Martian history.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA["Most of us understand that if there is to be life on Mars, it's not going to be roaming on the surface. ... but it could be thriving underground with the heat energy provided by volcanism," Humayun said.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[However, "if there hasn't been [volcanic activity in] 4 billion years, ... it would be very difficult to believe there was life left on Mars."]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[To settle the question, Desmond Moser of Western University in Ontario, Canada had his team examine a meteorite known as Northwest Africa 5298.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[They looked at very tiny deposits within it called baddeleyites.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[These tough, zirconium-rich minerals are "10 times smaller than the diameter of a human hair," said study co-author Axel Schmitt, a geochemist at the University of California, Los Angeles.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[Researchers generally measure relative amounts of pairs of radioactive elements in rocks to gauge how long a rock has been around since it fully crystallized.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[But that isotopic ratio can be reset by a big impact that melts the rock down, erasing the geochemical trail.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[That's why scientists picked the tiny baddeleyites: Once they form, they are durable little minerals.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[It's not easy to melt them down and reset their isotopic clock.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[By looking at the isotopic ratios of radioactive uranium and lead in this tough rock, the scientists found that it formed about 187 million years ago, give or take 33 million years.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[This confirmed that the baddeleyites were young.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[The scientists could also see evidence of the damage done to the meteorite by the event that may have released it from the Martian surface sometime around 22 million years ago.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[The shock from that impact muddled up the mineral structure inside, while keeping the chemicals themselves mostly intact.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[The result was something like shaking up a sealed gift box of chocolates.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA["It looks good on the outside, but all the pieces are dislodged on the inside," Schmitt said.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[The study further shows that the shergottites weren't old rocks, Humayun said.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[But that was what he had expected.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA["If they had found that it was 4 billion years old, I would eat my hat," he said.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[The researchers say they can use their method of dating these rocks to study other Martian meteorites.]]></answer>
		<answer isaudiomp3="1" picture="images/c1.jpg" mp3="AUDIO_REPOS/2063-1" isrationalemp3="1" rationalemp3="AUDIO_REPOS/right.mp3" rationaleimage="images/rationale/1.1.jpg" rationale="Right" value="1" choicesay=""><![CDATA[Their hope is that it will reveal new information about the Red Planet's geophysical inner life.]]></answer>
		
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