Kalliope is somewhat elongated, approximately 166 km in diameter,[3] and slightly asymmetric, as evidenced by resolved images taken with the VLT at the European Southern Observatory.

[3] Since the asteroid is likely to be a rubble pile, accounting for a possible porosity of 20–40% leads to the material density of 4.2–5.8 g/cm3, which means that Kalliope is probably made of a mixture of metal with silicates.

[3] Spectroscopic studies have shown, however, evidence of hydrated minerals[9] and silicates,[10] which indicate rather a stony surface composition.

In 2022, it was discovered that 22 Kalliope is part of an asteroid family that formed about 900 million years ago.

[3] Linus was discovered on 29 August 2001 by Jean-Luc Margot and Michael E. Brown, while another team led by William Merline also independently detected the moon 3 days later.