Halley's comet is a potato-shaped lump about ten miles long with a mass estimated at 10 billion tons, most of which is water ice.
I generally eschew this construction fearing that it is wrong except for some specific cases. I was surprised that the above sentence is grammatically correct.
Shouldn't something like this be more appropriate :
Halley's comet is a potato-shaped lump about ten miles long with a mass
estimated to be around10 billion tons, most of whichD is water ice.
PS: Also can these uses of 'estimated at' be grammatically correct too?
is estimated at50 kgs OR The elephant's weight
is estimated at500 kgss