Stakeholder #2, Blog Post 3.7

A good controversy does not have only one side arguing their case. Such a scenario would be just plain silly! The second stakeholder in my controversy are scientists who claim that it was asteroids, not comets, that brought water to the early Earth. This group has arguably grown the most from this controversy.

1.  Can you describe this stakeholder in 200-250 words?

Similar to stakeholder #1, this stakeholder is not any one specific person. It is a group of scientists that claim that asteroids brought water to Earth instead of comets. One such place to find many scientists who are a part of the stakeholder group is the European Space Agency (ESA). Kathrin Altwegg, the principal investigator for the Rosetta/ROSINA program, could be considered a "member" of the stakeholder group. She has made claims (listed under question 2) that the data from the Rosetta mission provides solid evidence that comets could not have brought water to the early Earth. Instead, it was asteroids.

This stakeholder group has popped up very recently. While there was a spattering of scientists who believed that asteroids were the main delivery system of water before the Rosetta mission, the data from the mission persuaded many more scientists to join the group. While the stakeholder group is young, it also has very recent data to back up their claims and a great deal of support. It will be interesting to see how future data will affect this stakeholder group.

2. Can you identify THREE specific claims being made by this stakeholder?

Claim #1: Asteroids were the main system of water delivery to the Earth, not comets. Kathrin Altwegg is quoted, "Our finding also rules out the idea that Jupiter-family comets contain solely Earth ocean-like water, and adds weight to models that place more emphasis on asteroids as the main delivery mechanism for Earth’s oceans.”

Claim #2: Despite claims that asteroids have less ice water than comets and are therefore not reliable mechanisms for water delivery, this stakeholder group claims that asteroids very well could have brought water. Kathrin Altwegg again stated that, "Today's asteroids have very little water — that's clear. "But that was probably not always the case. During the Late Heavy Bombardment 3.8 billion years ago, at that time, asteroids could have had much more water than they could now."

Claim #3: The water was delivered during the Late Heavy Bombardment Period (4.1 to 3.8 billion years ago). Charles Choi writes in his Space.com article, "prior studies have hinted that cosmic impacts could have easily brought water later, during a violent era known as the Late Heavy Bombardment, about 800 million years after Earth's formation."

3. Can you explain how valid these claims are?

Claim #3 is generally accepted as being a backed claim. Claims 1 and 2, however, might be a bit harder to back up. While the Rosetta mission did provide evidence against comets bringing water to Earth, more studies must be done. Only a handful of comets have ever been studied thoroughly enough to make predictions.

As well, it is hard to speculate just how much ice water asteroids contained 4.1 to 3.8 billion years ago. It could have been substantially more than we see in asteroids today, or the same amount we see in asteroids today. Claim #2 is therefore mostly conjuncture.

4. Can you explain how these claims are similar and/or different to the other stakeholders?

The Asteroid stakeholders and Comet stakeholders have at least one belief in common: both groups claim that celestial bodies in our solar system brought water to the early Earth. The difference is: what kind of bodies they were.

Asteroid stakeholders would be opposed to those scientists who claim that volcanic activity brought water to the Earth's surface. Earth didn't just start off with water, they claim. It had to come from somewhere else.

sammydavisdog. Hubble Finds Smallest Kuiper Belt Object. February 1st, 2010 via Flickr. Attribution License.