In Earth and Planetary Science Letters for April (vol. 679):
Libourel, G. Portail, M. Guigoz, V. et al. Low temperature brine formation by serpentinization on asteroid (162,173) Ryugu Art 119885 .119885
We know water existed in the early Solar System, and on some asteroids at that. We know silicates existed in the early Solar System, and in asteroids and comets to be specific. How do we know these? Because the combination of water and rock- hydrated minerals- still exists today. Meteorites contain clays (“phyllosilicates”) which are the ‘breakdown’ products when susceptible rocks are soaked in water. That water turns solid rock into clays, basically a mixture of mineral sheets and water bilayers at the microscopic scale. Clay is coherent but soft because, when you squeeze it, those mineral sheets are sliding against each other with water as a lubricant.
Now both Hayabusa2 and OSIRIS-REx have returned Ryugu and Bennu samples, respectively. Both samples include phyllosilicate minerals, basically the dominant component of both collections. Libourel et al. attempt to piece together the process by which we got our current samples. After solid rocks turn to clays, the remaining fluid gets concentrated in mineral solutes. Those solutes, and other minerals present in the young asteroid, result in secondary minerals. We now see those minerals.