The discovery marks the first time water has been found on the surfaces of asteroids.
Prior possible water discoveries on asteroids could simply have been hydroxyl mistaken for water.
In one plausible explanation, impacts from icy comets and moons from the outer solar system could havebroughtwater here.
However, this would have required unstable orbits from outer planets like Jupiter.
The recent discovery expands the potential number of places in the inner solar system that harbor water.
Additional investigation could widen the net further.
