The asteroid's efficiency in reflecting sunlight was its albedo.
Its "albedo," in other words, is 0·17, which is precisely that ascribed to the moon.
If the asteroid's albedo matched it, that would be one piece of evidence.
Its theoretical mean temperature, taking into account both distance from the sun and albedo, is 34° C. below freezing.
The telescopes showed Sennech's albedo down to a fraction of normal; that, he supposed, would indicate smoke in the atmosphere.
An albedo equal to that of Mars was assumed as the basis of the calculation.
If anything of the right size shows up, decelerate until we can get mass and albedo measurements.