Unsolved mysteries of our planet

1. We have not reached the Earth’s mantle
Seismologists believe that the inner core of our planet is solid and the outer is liquid and hot. Located above the mantle on which it slides, the crust of the Earth. However, we still do not know what is in this mantle, because not once in there did not get. It is located at a depth 30-2 900 km, and the deep “hole” that people dug is the Kola superdeep borehole in Russia, which goes back only some of 12.3 km.