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Date:         Thu, 29 Jun 2006 12:15:12 EDT
Reply-To:     [log in to unmask]
Sender:       "Ecological Society of America: grants, jobs, news"
              <[log in to unmask]>
From:         Wirt Atmar <[log in to unmask]>
Subject:      Re: Wall Street Journal op-ed on "An Inconvenient Truth"
Content-Type: text/plain; charset="US-ASCII"

Malcolm writes: > Furthermore, we > have observational evidence that the temperature differences among earth, > venus and mars are better explained by their greenhouse gas levels than by > their distance from the sun. There is a grain of truth in that statement, but unfortunately only a grain. Solar distances *are* the primary determinant of a terrestrial planet's history. The "habitable zone," the hypothetical region allowing persistent presence of liquid water around a host star, is determined primarily by the solar flux (IR, visible, and UV) at a that distance, along with the planetary body's size. Whatever greenhouse gases might exist in the planet's atmosphere at any one time are a complex result of that distance, the planet's internal heat and the origination of life on its surface and its adopted biochemistries. Venus, Earth and Mars all had oceans at the time of their formations, but Venus and Mars lost theirs within the first 500 Ma to 2 Ga for two different reasons, as it is estimated that the Earth will also in 500 Ma to 1 Ga. The moderator of the list requested that I stop posting the Lecture of the Week notices because of its current emphasis on astrobiology. I have absolutely no complaint about that. It is never my intention to offend. However, I do disagree a bit about the irrelevance of the lectures to ecology. Geology was the science that informed the evolution of evolutionary ecological thought during Darwin's time; comparative planetology will be the science that will do the same during ours in the coming years. Last week's lecture in the series was by David Grinspoon (SwRI, Boulder) on the planetary history of Venus's oceans and atmosphere. This week's lecture is by Matt Golombek (NASA JPL), the geologist most responsible for the site selections of the current Mars rovers, on the Spirit Rover's traverse of the Gusev Crater. For the first time, we have geologists on Mars, albeit automated and slow as the devil, but they're doing a magnificient job. Spirit's results in the ancient cratered highlands, which Golombek describes, indicate that Mars died geologically 3.5 Ga ago, and that whatever water existed on Mars was gone by then. Similarly, next week's lecture is by Steven Squyres (Cornell), the PI for the rovers, and he will talk about Opportunity's traverse of the Meridiani Planum, on the other side of Mars, a region that was demonstrably once deep in water. The following week's lecture will be by David Catling (U. Washington) on the evolution of the three planetary atmospheres (Venus, Earth and Mars). While these lectures look at the complete histories of the planetary volatiles on the interior terrestrial planets and are only of ancillary value to conversations about global warming, they should still quite interesting to listen to by any ecologist and do set the philosophical stage for discussions about global atmospheric stabilities. The lectures are available at: http://aics-research.com/lotw/ Wirt Atmar


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