Another otherworldly theory – at https://phys.org/print443181994.html … the diamond from the sky may have come from the 'lost planet' (but they are not talking about Planet X or 9). In this instance the theory is that the solar system was full of planets, proto planets, or wannabe planets very early on (4.5 billion years ago). The diamond was in a meteorite found in the Nubian Desert of the Sudan and was created under extreme pressure.
More revealing is the story at https://phys.org/print443351201.html … astronomers have probed the gas filled haloes around galaxies in the hope of finding the missing matter thought to reside there – but to no avail. Where exactly is the dark matter. Curiously, scientists studying nearby galaxies in recent years have found them to contain three times LESS normal matter than expected – and the Milky Way contains a half less normal matter than expected. Perhaps the calculation need re-evaluating. However, there is no intention of abandoning the search for dark matter as it is thought it must be there. Has it been ejected from galaxies into the space between star systems? Is it yet hiding in places that have not come under intense scrutiny.