New Clues on the Origin of Water on Earth

Last week has brought new evidence about the existence of water on our planet. The Herschel Infrared Space Observatory using HIFI, a very sensitive instrument for detecting water in the universe, has revealed that the comet Hartley 2 contains the same kind of water as Earth’s oceans, allowing the scientist to assume that comets must have played a significant role in the origin of water on our planet. [1] Such a discovery not only offers clues about how water reached our planet, but also reveals the fact that water with similar chemical composition must be present elsewhere in the solar system and the universe.

The origin of water on Earth is still a debatable issue, mainly because our planet seems to have been very hot and dry at its beginnings, and therefore water could have not been present on the planet at that time. Water and other volatile substances must have reached the surface of the planet at a later date. While one hypothesis for the origin of water has always been an impact with a traveling celestial body, such as comets or asteroids, the comets that have been previously studied did not contain the same type of water. As an example, a study done by Caltech researchers on the comet Hale-Bopp revealed the comet contains large amounts of heavy water with a high level of deuterium, while our oceans have a significantly less quantity of it. [2] Of a total of six studied comets originating in the Oort Cloud, none of them has revealed regular water in their composition.

However, by studying the comet Hartley 2 with the help of the Herschel Infrared Space Observatory, scientists have discovered that the vaporized water in the comet’s coma contains both heavy water and regular water as the one on Earth’s surface. Hartley 2 comes from the Kuiper Belt, while the previously studied comets are believed to come from the Oort Cloud. It is now believed that comets in the Kuiper Belt have more regular water than the ones coming from the Oort Cloud. [3] The percentage of heavy vs. regular water in the comet has generated the conclusion that comets must have contributed with at least ten percent of Earth’s water, with asteroids being the primary source, and all the planets in the inner solar system must have gotten their water from the same source.

The Herschel Space Observatory will be studying other comets from the Kuiper Belt to make sure Hartley 2 is not an exception.

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Notes

[1] European Space Agency (ESA). Did Earth's oceans come from comets? October 5, 2011. http://www.esa.int/SPECIALS/Herschel/SEMER89U7TG_0.html (Accessed October 10, 2011), para. 8.

[2] Tindol, Robert. Earth's water probably didn't come from comets. Caltech, 2011. http://neo.jpl.nasa.gov/news/news008.html (Accessed October 10, 2011), para. 2-3.

[3] Brown, Dwayne, Clavin, Whitney. Space Observatory Provides Clues To Creation Of Earth's Oceans. NASA, October 5, 2011. http://www.nasa.gov/home/hqnews/2011/oct/HQ_11-338_Herschel_Comet_Water.html (Accessed October 10, 2011), para. 5.

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References

Brown, Dwayne, Clavin, Whitney. Space Observatory Provides Clues To Creation Of Earth's Oceans. NASA, October 5, 2011. http://www.nasa.gov/home/hqnews/2011/oct/HQ_11-338_Herschel_Comet_Water.html (Accessed October 10, 2011).

European Space Agency (ESA).  Did Earth's oceans come from comets? October 5, 2011. http://www.esa.int/SPECIALS/Herschel/SEMER89U7TG_0.html (Accessed October 10, 2011).

Tindol, Robert. Earth's water probably didn't come from comets. Caltech, 2011. http://neo.jpl.nasa.gov/news/news008.html (Accessed October 10, 2011).