Scientists from the MESSENGER mission continue to analyze the data from the spacecraft's first flyby of Mercury on January 14, 2008. Initial data about the planet's gravity field grabbed the science team's attention, as the actual gravity data differed from predictions based on the Mariner 10 flyby in 1975. Any unknowns in [...]

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I wish they were more specific: Was the mascon modeled to account for greater or less gravitational braking than expected? We have discussed this before, but we still don't have an answer. (Since I predicted less, I would really like an answer!)

Modeling of a mascon could be consistent with either result, just as the timing in the push near the apex of a swing can either increase or decrease the momentum of the swinger.

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jwj

If you always believe what you already know, you can't learn anything - Liz

The mascon was modeled to make the path data match gravitational acceleration. You should be able to tell wether Messenger was faster or slower off of the position of the mascon at closest approach.