The oceans cover about 70 percent of the Earth's surface. Ocean water contains salts and we say that ocean water has a certain salinity. You are very familiar with a salt: NaCl. But there are other salts in the oceans. Scientists estimate that if the salt in the oceans could be removed and spread evenly over the Earth's land surface it would form a layer more than 500 feet thick, about the height of a 40-story office building (NOAA). Scientists also believe that the amount of salt in the Earth's oceans remains pretty constant. Salt water - fresh water. Where did the salt in the oceans come form?

The salt in the oceans comes from weathering and the erosion of the earth's crust.

Explanation:

The weathering can be described as the breaking down of rocks.

During the weathering of rocks, minerals will be dissolved from the land and salt is one of them. These minerals (salt included) will then be delivered into the oceans by erosion of the Earth's crust.

Erosion can be aided by wind, ice or water. Erosion removed weathered materials. When these weathered materials are removed, new materials (rocks) will be exposed to weathering thereby promoting continuous weathering processes

i'd say that the moon rock is about 2.2 billion years old.