Re: Gravity mapping and the Earth

[John Kineman <***>]

Judith,

We have a gravity data program here at NGDC. Take a look at:
http://www.ngdc.noaa.gov/seg/gravity/welcome.shtml

One of the things you can do with gravity data is map the relief of the
Earth, because mountains add mass and thus increase the local gravity.
I used to be the gravity officer in the '70s. on the NOAA Ship
Oceanographer - you can actually measure gravity at sea using very
sophisticated equipment.

JK

Judith Rosen wrote:

> While at the Dentist's office last week, I started reading the Feb 2004
> National Geographic magazine and discovered a fascinating article-- with
> pictures-- about a joint US/German effort to use a pair of satellites to map
> the fluctuations in Earth's gravity. The project is called GRACE (Gravity
> Recovery and Climate Experiment). The color-coded map they provide is quite
> dramatic, with some fascinating surprises (to me, anyway) on it:
>
> Some areas of the ocean have "more gravity" than many mountain ranges, while
> other areas of the ocean have the least gravity on the surface. Land and
> water don't seem to have much correlation in gravitational terms; certain
> areas of land are very low on the gravity scale and certain areas of ocean
> are very high... Why?
>
> There is no mention of whether the gravitational effects of the moon over
> time (as the measurements were taken) were factored in and subtracted out or
> what kind of fluctuation the moon causes in various phases of its orbit,
> etc. I think the measurements are meaningless if they don't do all of that.
>
> Does anyone know of this project?
>
> Judith