Why Are Earth's Oldest Rocks Younger Than Mars's?

[Kessler]

Having trouble with some homework. Why are there no rocks found as old as Earth is (apx. 4.5bil yrs)? Why are most rocks on Mars at least 3mil yrs old?

 

[ray b]

stuff happens
rocks doNOT just sit there
they turn to sand/dirt/dust over 4.5 B Y
melt or get buryed and pressed into other forms

 

[mgb_phys]

Weathering and plate techtonics
There isn't much of Earth's surface that has been surface for 4Billion years.
Mars is relatively inactive, the surface has largely always been the surface.