Read the text below to answer questions 15-17.
Solar System’s Water is Older Than the Sun
Next time you’re swimming in the ocean, consider this: part of the water is older than the sun.
So concludes a team of scientists who ran computer models comparing the ratios of hydrogen isotopes over time. Taking into account new insights that the solar nebula had less ionizing radiation than previously thought, the models show that at least some of the water found in the ocean, as well as in comets, meteorites and on the moon, predate the sun’s birth.
The only other option, the scientists conclude, is that it formed in the cold, intersteller cloud from which the sun itself originated.
The discovery, reported in this week’s Science, stems from the insight of lead author Lauren Ilsedore Cleeves, a doctoral student at the University of Michigan, who realized that planetforming disks around young stars should be shielded from galactic rays by the strong solar winds, dramatically altering the chemistry occurring inside the disks, said Conel Alexander, with the Carnegie Institution of Washington.
“The finding... makes it quite hard for these regions in the disk to synthesize any new molecules. This was an ‘aha’ moment for us – without any new water creation the only place these ices could have come from was the chemically rich interstellar gas out of which the solar system formed originally,” Cleeves wrote in an email to Discovery News.
“It’s remarkable that these ices survived the entire process of stellar birth,” she added.
The finding has implications for the search for life beyond Earth, as water is believed to be necessary for life.
“If the sun’s formation was typical, interstellar ices – including water – are likely common ingredients present during the formation of all planetary systems, which puts a wonderful outlook on the possibility of other life in the universe,” Cleeves said.
In addition, it’s not just water that likely survived the solar system’s birth.
“The same must be true for the organic matter that we know is present in molecular cloud ices. So I think this strengthens the case that we have interstellar organic matter in meteorites and comets too,” Alexander wrote in an email to Discovery News.
Available in: http://news.discovery.com
Read the sentence taken from the text.
“The finding has implications for the search for life beyond Earth, as water is believed to be necessary for life.”
Choose the alternative in which the underlined word is conjugated in the same verb tense as the one above.