For the curious, Richard Lachapelle, B.Sc, Eng. Applications Geophysicist at Scintrex Limited has provided the following expanation:
The attached document, taken from a geophysics course at the University of Alberta, gives an approximate method to determine the excess mass of a spherical object (an approximation of the Chelyabinsk meteorite).
The formula is M=g * z2/G,
where: M is the excess mass, in Kg
g is the gravity anomaly in m/s2, as measured by the
CG-5 Autograv Gravity Meter illustrated in the pictures in the link below
Z is the distance from the gravity sensor to the centre of the meteorite
(in meters)
G is the Universal Gravitational Constant
Here's an image of the first page of the method's description.
- Gravity Anomalies
If anyone wants a copy of the original pdf document, then drop me a private message.
Many thanks to Richard, and the team at Scintrex, for the excellent explanation.
Next question is obviously what was the result. Any offers? I's say at least ten Lake House meteorites mass....