Primigenia I (body 3) and Primigenia II (body 3 a) are similar sized, only with a 748 km difference in radius, with Primigenia I being slightly larger. However what is interesting is that both planetary bodies house complex life, in extremely different environments.

Primigenia II features a sulphur dioxide atmosphere that is constantly bombarded with carbon dioxide geothermal activity, which has helped foster life. Both Recepta Deltahedronix and Bacteria Tela are abundant near the geysers, which also feature Fumerola Carbosis.

According to the data collected so far, as of 3308/10/24 this is one of only five known thin atmospheric landable moons orbiting a parent Earth like world, and probably the only one closely resembling its parent in size and planetary characteristics.