Rosetta flew within 800 kilometers of the asteroid Steins,
yet no gravity data, or mass data on asteroid Steins has been released.

I still don't know the mean density, mass or surface gravity of Steins.
Was that part of Rosetta's mission a failure?
Why isn't ESA saying anything?

Spacecraft Galileo was considered a partial failure, yet returned 14,000 images, 30 gigabytes of data.
Galileo's flyby of the asteroid, Gaspra, revealed that it has a mass of 10^16 kilograms. It's dimensions are known as well, so a surface
gravity value and a mean density of Gaspra can be obtained I guess
using Newton's laws.

And spacecraft Galileo flew 1,600 kilometers from Gaspra.