On November 4, 2010, at about 10:00 EDT, NASA's EPOXI spacecraft did a flyby of comet 103P/Hartley 2, which had been observed for months by the Hubble Space Telescope. It was only the fifth time that a spacecraft has visited a comet. The small comet called Hartley 2 came within 434 miles of the spacecraft, and scientists are hoping that data from the encounter will help them better understand more about the formation of the solar system, as well as the role of comets in Earth's early history, specifically the question of whether comets were the main factors providing the planet with molecules conducive to life.
Comets and Oceans
Because comets are essentially large balls of ice, for many years experts hypothesized that comet impacts on the early Earth may have provided some or most of the water that eventually filled the planet's oceans. Because comets also generally contain some organic compounds, there was also speculation that comets seeded the waters with the building blocks of life. However, closer studies over the past two decades revealed that the ratio of deuterium to hydrogen atoms in the comets observed does not match the ratio seen in oceans on Earth.
Kuiper Belt vs. Asteroid Belt
But these comets, like most other short-period comets, originated in the remote Kuiper belt beyond the orbit of Neptune. Data from comets emerging from the closer asteroid belt beyond the orbit of Mars show a wider range of deuterium-hydrogen ratios, some of which are similar to the ratio found in Earth's oceans.
Researchers point out that this does not necessarily mean that all or even most of the water in the oceans originated from asteroid belt comets; the ratio of deuterium to hydrogen might not be consistent over time, for example. Additionally, the ratios of some other comets originating from the very distant Oort cloud have yet to be measured.
Hartley 2 and Organic Compounds
It is still unclear how much, if any, of the water and organic molecules on Earth originated from comet impacts. The November 4th flyby of Hartley 2 — the roughly 1-mile-wide ice chunk that looks something like a chicken drumstick and strangely spews a large amount of gas laced with cyanide — will hopefully shed more light on the question, and bring researchers closer to an understanding of life's origins on the planet.
Sources:
Choi, Charles Q. "How Earth May Owe Its Life to Comets." LiveScience. 3 Nov. 2010. Web. 04 Nov. 2010.
Wall, Mike. "First Close-up Photos of Comet Hartley 2 Reveal a Space Peanut." LiveScience. 4 Nov. 2010. Web. 04 Nov. 2010.
Jenny Ashford - Jenny Ashford is a writer and graphic artist from central Florida. Her main area of interest in her Suite 101 articles is science, with a ...
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