Story URL: http://news.medill.northwestern.edu/chicago/news.aspx?id=189857
Story Retrieval Date: 5/21/2013 2:15:57 PM CST
Comet Hartley 2 contains ocean-like water, leading astronomers to believe comets could have contributed more to Earth's water than previously believed.
Could Earth's water have come from comets?
New evidence from a comet known as Hartley 2 supports the theory that the balls of ice and dust delivered a significant portion of Earth's ocean waters, reported University of Michigan astronomers today online in Nature.
"Life would not exist on Earth without liquid water, and so the questions of how and when the oceans got here is a fundamental one," said astronomer Ted Bergin, one of the researchers from the University of Michigan in Ann Arbor. "It's a big puzzle, and these new findings are an important piece."
The Michigan researchers concluded comets could have been responsible for more than 10 percent of Earth’s water and believes this discovery could lead to more research related to space and water.
Larry Ciupik, an astronomer at the Adler Planetarium in Chicago, agreed with the findings.
“This means that there is a place where you can find pure ocean-like water,” he said. “At some point in the future, you can imagine people directing comets into Earth’s oceans to help subsidize whatever water you might need there. It’s that big of a deal that you could actually help with droughts.”
Ciupik said that this is an important discovery for researchers and future scientific endeavors.
“People are worried about global warming, right? Well, what if you wanted to cool down the ocean? You could do that with a very big ice cube,” Ciupik said. “Comets could be used to add water to places that don’t have much and provide environments for us to live more comfortably.”
Bergin and colleagues found that the ice on Hartley 2 has the same chemical composition as oceans on Earth. The comet ice and ocean water have similar D/H ratios, which is the proportion of deuterium, or heavy hydrogen, in the water. A deuterium atom is a hydrogen with an extra neutron in its nucleus.
“The prevailing theory is that the Earth formed dry, and, therefore, you need to look for other sources of water farther away,” Bergin said.
The researchers obtained their data from the Herschel satellite, an orbiting telescope launched about two years ago by a European Space Agency mission with NASA. The satellite can detect traces of water, allowing astronomers to observe at the far-infrared wavelengths.
Astronomers have debated and theorized about the source of Earth's oceans for decades. This was the first time ocean-like water was detected in a comet. Previously, asteroids were believed to have provided most of our ocean water. Six other comets measured in recent years had a much different D/H ratio than Earth’s oceans, meaning they could not have been responsible for more than 10 percent of Earth's water.
The astronomers hypothesize that Hartley 2 most likely formed in the Kuiper belt, near Pluto, about 30 times farther from the sun than the Earth.
“We have never until now had the measurement of a comet that came from the Kuiper belt,” Bergin said. “We had this potential other reservoir of water that could have potentially supplied water to the Earth, and we had no measurement of its isotopic signature or deuterium to hydrogen ration until now.”
The reservoir of material that has ocean-like water in the solar system is much larger than they thought before, Bergin said. However, researchers cannot identify exactly which asteroids or comets brought water to Earth.
“Our theoretical expectations were completely incorrect, and, as a theorist, I was humbled,” Bergin said. “Kuiper belt comets have a lower D/H ratio than models had predicted.”
Despite the human space shuttle program recently shutting down in the United States, Bergin said there is still a strong interest in science and astrophysics.
“As a nation, it is in our best interest to try and encourage more young people to consider science and to expose them to science as early as they can,” Bergin said. “It would be great if we could try to direct ourselves to a goal of getting more scientists.”