How old is the planet Mercury?
It is believed that all of the planets, from Mercury to Neptune,
formed around the same time, about 4.95 billion years ago.
Presumably, Mercury is of similar age to Earth.
The only way to be sure, of course, would be to land on the surface
and use radioisotope dating to determine the age of the rock. Such
a mission is not planned and probably will not be undertaken in the
next 25 years.
it is40000000,56780 years old!