1. Can you describe this stakeholder in 200-250 words?
As stated earlier, this stakeholder is not one specific person or scientist. This stakeholder is a community of scientists that, more or less, make the same claims about comets and their impact on the evolution of the planet Earth. They have no specific website or headquarters. These scientists work at universities and institutions around the world; including NASA and the European Space Agency (ESA). One such scientist is Gören Pilbratt, a Project Scientist for the ESA's Herschel Program. He was a member of the team that discovered water with very similar chemical properties to Earth water on the comet Hartley 2. The discovery of this water was the main event that set the controversy in motion.
Recently, this stakeholder group has had their claims come under intense scrutiny. When discovering that comet Hartley 2 had water with similar chemistry to Earth water, many media and science publications wrote articles detailing the data from the space mission and how it could impact the scientific community. In 2014, however, the narrative changed. ESA's Rosetta mission discovered water on a different comet, 67P, that was very different from Earth water. After this discovery, many media publications stated wholeheartedly that Earth's water probably didn't come from comets at all.
Despite this, the stakeholder group still remains. More analysis of comets is needed before any precise answer to the controversy can be found.
2. Can you identify THREE specific claims being made by this stakeholder?
Claim #1: Comets have a great deal of ice water. The ESA is quoted in one of their published articles as saying that comet 67P does, "indeed include a significant amount of water ice."
Claim #2: Comets have water chemistry similar to that of Earth's water. Gören Pilbratt stated in another ESA article that, "The unique sensitivity and spectral resolution of the HIFI instrument flown on board Herschel enables us to observe different isotopologues of water in comets. As this result clearly demonstrates, HIFI observations are shedding new light on the possible origins of water on Earth."
Claim #3: The comets brought water to the Earth early in its history. According to planetary scientists, this process occurred during the Late Heavy Bombardment Period about 4.1 to 3.8 billion years ago. Carey Lisse of Johns Hopkins University Applied Physics Laboratory is quoted as saying, “Where the comets are hitting the rocky bodies is in the habitable zone around this star, so not only are life-forming materials possibly being delivered to rocky worlds, but also in the right place for life as we know it to grow".
3. Can you explain how valid these claims are?
Claims 1 and 3 have been backed by scientific study. The Rosetta mission did indeed find ice water on comet 67P and the theory that Earth was created from accretion and impacts of several rocky bodies in our solar system is well supported.
Claim 2, however, may be harder for scientists to believe. The Rosetta mission also found that water on comets can vary wildly. This would mean that even a handful of comets with heavier water than is seen on Earth could tip the balance. For many, the Rosetta mission appeared to doom the comet water theory to the dustbin of scientific theories.
4. Can you explain how these claims are similar and/or different to the other stakeholders?
The claims of Comet Theorists are very similar to the claims of scientists who believe that it was asteroids that instead brought water to the planet. Both stakeholders believe that it was celestial bodies that brought Earth most of its water, not processes such as volcanic activity. However, these claims stand in stark contrast to the claims of scientists who believe that volcanic processes released water vapor in to Earth's early atmosphere.
Don Davis. Planetoid crashing into Primordial Earth. Original work completed March 27th, 1991. Uploaded to wikimedia on October 9th, 2010. Image released to the public domain.
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