The Goldilocks Effect

Compare Earth to its nearest planets—Venus and Mars. The atmosphere of Venus is so thick that observers cannot see the surface of Venus from Earth. (Our only images of Venus s surface have come from probes that parachuted through Venus s atmosphere to the surface, and then promptly melted.) As a result, Venus experiences a runaway greenhouse effect that keeps Venus too hot to support liquid water or (probably) Ufe as we know it. Humans could not Uve on Venus. 

On the other hand, at the present time Mars has very little atmosphere. (It is believed by some planetary scientists that Mars may have had an atmosphere in the past but lost that atmosphere to outer space.) Consequently, there is no greenhouse effect on Mars, and Mars stays permanently cold. Mars is so cold that all surface water on Mars is frozen. Humans could Uve on Mars only in space suits or in artificial shelters. 

Suppose the fairy-tale character Goldilocks were to visit Venus, Mars, and Earth. In the fairy tale, she said that Papa Bear s soup was too hot. Mama Bear s soup was too cold, but Baby Bear s soup was just right (and she ate aU of it, much to the dismay of Baby Bear). Goldilocks would draw the same conclusions about these three planets—Venus is too hot. Mars is too cold, but Earth is just right. The whole idea behind the efforts to reverse any accelerated global warming trends is to keep Earth the way it is— just right for the life that currently inhabits it. 

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Too little COj (as is the case on Mars), and Earth would be too cold—water would only be present as ice, which would make it difficult for Earth s surface to support life as we generally know it. Too much CO (as is the case on Venus), and Earth would be too hot—water would only be present in the gaseous state, which would also make it difficult for Earth to support life as we know it. It s the Goldilocks effect Venus is too hot. Mars is too cold. Earth is just right. To a large extent, it is CO that is helping to maintain the right balance. 

For 6 and 7, the half-lives for beta-blocking activity in an in-vivo dog model were found to be 30 min and 60 min, respectively. Assuming that this difference reflected simple steric effects, it was speculated that hydrolysis might be even quicker for esters placed further from the bulky phenyl ring. To address this hypothesis, compound series 8 was prepared. These compounds and their corresponding half-life data are shown in Fig. 9.2 [12]. The Goldilocks nature [20] of 8 where n= 2, likely reflects the removal of the steric impediment caused by the... 

On a Goldilocks planet the surface temperature is just right. Where volcanism occurs, water is ejected from the interior, but is held under the cold trap until it can be returned to new crust via hydrothermal systems. Old plate is dense and falls in the water returns to the interior. Much of this water fluxes melt and is returned at andesitic volcanoes. A small amount is retained by plate entering the deep mantle. This intake is controlled by the ambient temperature and in effect the system becomes self-fluxing. If it is locally too hot, abundant melt production removes water and heat. As the planet cools, andesitic melt production falls and the cooler deep mantle accepts more water, to allow melt production to continue at mid-ocean ridges. All this depends on a surface temperature that allows rehydration and cooling of the new plate. 

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